Glossary of astronomy

2813: 6979: 322: 12141: 5427: 7677: 3940: 10507: 9432: 9292: 3388: 16724: 13627: 16736: 1817: 9003: 8694:, which can be difficult to continuously track because of their size and great distance from Earth. Very short observation arcs, e.g. where the time between the initial observation and the most recent observation is less than 30 days, are of limited descriptive power because they represent only a very small fraction of the total path traced by the object in its 1481: 13606:, and is useful in specifically identifying small bodies observed before and after planetary encounters, as its numerical value remains largely constant throughout the body's lifetime. It is also used to distinguish between different kinds of orbits which are characteristic of different classes of bodies. 12435:

that has an anomalously high rate of star formation. The criteria for a starburst is a star formation rate that would normally consume the galaxy's available supply of unbound gas within a time period shorter than the age of the galaxy. Most starbursts occur as a result of galactic interactions, such

13992:

that is observed to vary in brightness. This variation may be periodic, with one or more cycles that last hours, days, months, or even years. Some stars vary in an irregular manner, while others undergo cataclysmic changes in brightness. Other forms of variability are intrinsic changes to the star's

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The time period immediately before sunrise and after sunset during which, despite the Sun being completely below the horizon, the scattering of sunlight by the Earth's atmosphere supplies significant illumination to the ambient environment. Several definitions of twilight are commonly distinguished,

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which appear near each other on the celestial sphere, either because the two stars coincidentally lie along nearly the same line of sight from the Earth, though they are in fact physically distant from each other, or because the two stars are actually located in physical proximity to each other, by

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The human eye as used without any magnifying or light-collecting optical aid, such as a telescope, nor any eye protection. Many astronomical objects emit or reflect visible light that is sufficiently bright to fall within the limits of normal human visual perception, allowing observers to see them

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A branch of astronomy that uses analytical and computational models based on principles from physics and chemistry to describe, explain, and model the properties of astronomical objects and phenomena, with the ultimate goal of accurately predicting the observable or testable consequences of those

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between the Sun and the Earth. Because all three bodies are continuously moving, the shadow of the Moon traces out a narrow path across the Earth's surface, and from any given location within or very close to this path, the eclipse is visible only for a short duration. Depending on the observer's

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that are cooler and less massive. The term originated from historical stellar models that assumed stars began their early life at a high temperature then gradually cooled off as they aged. It may be used to refer to the higher-temperature members of any particular population or category of stars,

314:) to 1 (indicating total reflection). The albedo reported for an astronomical body may vary widely by the spectral and angular distribution of the incident radiation, by the "layer" of the body being measured (e.g. upper atmosphere versus surface), and by local variation within these layers (e.g. 3694:

and change over time. The primary use of astronomical quantities specified by epochs is to calculate other relevant parameters of motion in order to predict future positions and velocities. In modern usage, astronomical quantities are often specified as a polynomial function of a particular time

10786:

A grid of fine lines or crosshatches engraved upon a transparent glass plate, which when placed in front of film during a photographic exposure produces a corresponding grid in the resulting photograph by creating permanent shadows on the film negative. These grids are used in some photographic

6329:, which is a plot of stars having the same mass but differing ages. In fact, multiple evolutionary tracks can be used to build isochrones by putting curves through equal-age points along the tracks. When the mass of a star can be determined, an isochrone can be used to estimate the star's age. 10825: 3594: 1315:

A gaseous envelope held in place by the gravity of a planet. This shell of gas has no clearly defined exterior boundary, but instead grows increasingly tenuous with altitude. The term can also be applied to a stellar atmosphere, referring to the visible outer layers of a

9641:

is not an accurate representation of the body's actual orbit. Perturbing forces may include the gravitational forces exerted by any number of additional bodies, the off-center gravitational forces which are consequences of bodies not being perfectly spherical, and/or

8386:

A type of elementary particle, electrically neutral and with an extremely small rest mass, that interacts with other particles only via the weak interaction and the gravitational interaction. Neutrinos therefore typically pass through normal matter unimpeded and

5528:

and other elements. Because O-type stars have relatively short lifetimes (typically a few million years), the presence of an H II region indicates that massive star formation has taken place recently at that location. H II regions are often found in the arms of

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The minimum speed that must be achieved for a free, non-propelled object to escape from the gravitational influence of a massive body, i.e. to achieve an infinite distance from it; more generally, escape velocity is the speed at which the sum of an object's

3417:

23.4 degrees with respect to the ecliptic. To an observer on Earth, this means that the path the Sun appears to follow upon the celestial sphere is not a straight line (i.e. the ecliptic does not appear "flat"). Twice during each complete orbit, at the two

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in the Northern Hemisphere, is the annual date featuring the longest duration of daylight and the shortest duration of nighttime for any given point in the Northern Hemisphere; the reverse is true in the Southern Hemisphere, where the June date is the

6963:). There are also intermediate phases, during which the visible side may be only partially sunlit, e.g. when the Moon appears as a crescent. During the part of the lunar cycle in which the illuminated portion is growing larger, the Moon is said to be 10518:

when its position as viewed from Earth is at a right angle to the direction of the Sun. In such cases the moon or planet appears to be in its quarter phase (or nearly so), where half of the body is illuminated by the Sun and the other half is in

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positioned at a focal point of each ellipse. The word "orbit" can variously refer to the elliptical trajectory itself or the act of following this trajectory, and can refer to a stable, regularly repeating trajectory as well as a non-repeating

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at which a smaller object will maintain a constant position relative to the larger bodies. At other locations, a small object would eventually be pulled into its own orbit around one of the large bodies, but at the Lagrangian points the

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all align in a way that causes the small object to become "locked" in a stable or nearly stable relative position. For each combination of two orbital bodies, there are five such Lagrangian points, typically identified with the labels

12523:, located above the stellar core, radiation zone, and convection zone. Although it constitutes only a small portion of the star's mass, for some evolved stars the stellar envelope can encompass a significant fraction of the radius. 8876:

The positioning of two celestial objects on opposite sides of the sky, from the perspective of an observer. This occurs, for example, when a planet makes its closest approach to the Earth, placing it in opposition to the

7101:, where the lower the value, the brighter the object. By convention, a first magnitude star is 100 times as bright as a sixth magnitude star. Magnitude 6 is considered the lower limit of objects that can be seen with the 6445:(or sometimes a straight line) in three-dimensional space. Kepler orbits are idealized mathematical constructions which consider only the point-like gravitational attraction of two bodies, neglecting more complex orbital 942:

A field that studies the geology of solidified bodies such as the planets and their moons, asteroids, comets, and meteorites. Investigations are centered around the composition, structure, processes, and history of these

11640:, in which a portion of the Earth passes through the shadow cast by the Moon, temporarily blocking sunlight, fully or partially, from reaching that portion of the Earth's surface. A solar eclipse occurs when the Moon is 10699:

point and extends toward the higher luminosity and lower temperature range until reaching the red-giant tip. This branch consists of older stars that have evolved away from the main sequence but have not yet initiated

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seconds each. Because these are units of constant duration, the Julian year is also constant and does not vary with a specific calendar or with any of the other means of determining the length of a year, such as the

2465:

as a bright glow surrounding the lunar disk. The temperature of the corona is much higher than that of the stellar surface, and the mechanism that creates this heat remains subject to debate among astronomers.

11579:) on consecutive days. Because the Earth's orbit around the Sun affects the angle at which the Sun is seen from the Earth, the Sun appears to take slightly longer to return to the same position than do the 7657:

and is estimated to contain 100–400 billion stars and at least that number of planets. The Solar System is located on the inner edge of one of the Milky Way's spiral arms, about 27,000 light-years from the

12144:

The Earth's atmosphere permits certain wavelengths of electromagnetic energy to pass through but reflects or absorbs others, making it difficult or impossible to detect them from the surface. As a result,

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between the orbital periods of two planets (small bodies), both of which are orbiting a large central star. The inner planet completes two revolutions in the time it takes the outer planet to complete one.

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of gas will begin to undergo collapse and form stars. A cloud can become unstable against collapse when it cools sufficiently or has perturbations of density, allowing gravity to overcome the gas pressure.

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Rodono, M.; et al. (September 1986), "Rotational modulation and flares on RS CVn and BY Dra-type stars. I - Photometry and SPOT models for BY Dra, AU Mic, AR Lac, II Peg and V 711 Tau (= HR 1099)",

8552:

The quantity of some specified particle or object class per unit volume. For atoms, molecules, or subatomic particles, the volume is typically in cm or m. With stars, cubic parsecs (pc) are often used.

3781:, and a right-handed convention. This system is widely used to specify the positions of celestial objects as viewed from Earth. It may be implemented in either spherical or rectangular coordinates. 1189:, and their appearance in scientific literature has become increasingly infrequent. Exceptions include the symbols for the Sun (☉), the Earth (🜨), and the Moon (☾), which are sometimes used for 8122:. Because these four extrasolar messengers are created by different astrophysical processes, their presence or absence during a celestial event can reveal useful information about their sources. 9662:

or angle between an orbiting body and the Sun as viewed from a particular perspective, such as the Earth. It determines the amount of a planet or moon's visible surface that lies in shadow.

9331:, or its speed relative to the center of mass of the most massive body in the system. The term may be used to refer to either the mean orbital speed, i.e. the average speed over the entire 5867:

at a ground observer's particular location, the concept of the hour circle is employed to describe the longitudinal position of a celestial object relative to the observer's local meridian.

1551:, the barycenter may actually be located within the radius of the star, such that the planet appears to orbit the star itself, though both bodies actually orbit the shared barycenter. 5211:

or to the position of an observer, i.e. as defined by a straight line between the center of the Earth (or the observer) and the object at a given time, without any corrections for

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and a vast region of space beyond it. Its outer limit is often considered the boundary between matter originating from the Sun and matter originating from the rest of the galaxy.

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The apparent boundary between the surface of a celestial body and its sky when viewed from the perspective of an observer on or near that body's surface; more specifically, the

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within its core. Astronomers can determine the mass, age, platemperature, chemical composition, and many other properties of a star by observing its motion through space, its

9512:

For a variable star, this is the highest amplitude achieved during a rise in luminosity, followed by a decline. This data point can provide useful distance information for a

173:

star having spectra dominated by Balmer absorption lines of hydrogen. Stars of spectral class A are typically blue-white or white in color, measure between 1.4 and 2.1 times

5191:) disk with the same cross-section. It is a measure of how much of the incoming illumination is being scattered back toward an observer and has a value between zero and one. 10937:

matches an orbiting body's gravitational self-attraction. Inside this limit, the tidal forces will cause the orbiting body to disintegrate, usually to disperse and form a

6840:. The angle is typically measured eastwards from the reference direction to the ascending node (i.e. counterclockwise as seen from the north). It is one of six canonical 2306:

or share a common origin, or they are known to be gravitationally bound (in which case their proper motions may be rather different but average to be the same over time).

873:

An interdisciplinary field that studies the origins, evolution, distribution, and future of living systems in the universe, encompassing research on organic compounds in

10356:

and has since undergone internal melting to produce an interior of non-uniform composition. Protoplanets represent an intermediate step in the formation of a full-sized

7279:, the mean anomaly does not correspond to a real geometric angle but is instead a contrived parameter used to make calculating the position of the orbiting body in the 7444:

by collisions with air molecules in the upper atmosphere, leaving an ionization trail as a result of its rapid motion and sometimes also shedding material in its wake.

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that is illuminated by direct sunlight as viewed from Earth. This shape is referred to as a phase because it gradually changes in a regular cycle over the course of a

14085:. Since most absorption lines are caused by elements other than hydrogen and helium—what astronomers refer to as "metals"—these are sometimes called metal weak stars. 13380:

galaxy where the spiral arms are found and where most of the star formation takes place. It is about 300–400 parsecs (980–1,300 light-years) deep and centered on the

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on consecutive nights. The Earth's sidereal day is equal to approximately 86,164.09 seconds (23 hours, 56 minutes, 4.09 seconds), about four minutes shorter than the

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The main physical body of a gravitationally bound, multi-object system. The primary constitutes most of the system's mass and is generally located near the system's

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and the other known planets, such that it appears to be "detached" from the rest of the Solar System. Detached objects are thus distinct from other populations of

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over the course of one day. Diurnal motion is caused by Earth's rotation about its own axis, such that every object appears to follow a circular path called the

2421:

surrounding a specific and identifiable grouping of stars. The names of constellations are assigned by tradition and often have an associated folklore based in

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A concentration of mass formed out of the contraction of a collapsing interstellar cloud. Once sufficient mass has fallen onto this central core, it becomes a

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Bychkov, V. D.; et al. (April 2009), "Catalogue of averaged stellar effective magnetic fields - II. Re-discussion of chemically peculiar A and B stars",

6182:. This effect causes more distant objects such as stars to appear redder and dimmer than expected. It is not to be confused with the separate phenomenon of 2405:

as observed from a third body (usually the Earth), such that, from the observer's perspective, the objects appear to closely approach each other in the sky.

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A list of astronomical objects, typically grouped together because they share a common type, morphology, origin, means of detection, or method of discovery.

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as they pass in front of their host stars. A transit by an object that appears roughly the same size or larger than the body it is transiting is called an

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A concentration of mass so compact that it creates a region of space from which not even light can escape. The outer boundary of this region is called the

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The process of separating out different constituents of a planetary body, causing it to develop compositionally distinct layers (such as a metallic core).

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which are so distant from observers on Earth that they do not appear to move relative to each other, as opposed to the "foreground" of objects within the

16766: 14383: 8682:, which defines the length of the path traced by the object between these same observations. The term is primarily used in the discovery and tracking of 8627:

which are not gravitationally bound to each other, but move together through space in a loose association. The OB in the name is a reference to stars of

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from the Earth's surface without any special equipment. Vision corrected to normal acuity using eyeglasses or contact lenses is still considered unaided.

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2. The hazy band of light itself, which from Earth appears as a band because the galaxy's disk-shaped structure is viewed side-on from within.

308:

away from the body. It is a dimensionless quantity typically measured on a scale from 0 (indicating total absorption of all incident radiation, as by a

16888: 12009:

and flowing outwards at up to 900 kilometres per second (2,000,000 mph) into interplanetary space. Phenomena influenced by the solar wind include

11390:), measured as the time it takes for the fixed stars, as viewed from a particular point on the object's surface, to return to the same position in the 2219:. Because the energy output of a star varies by frequency as a function of temperature, the color index can be used to indicate the star's temperature. 2331:

with a very high mass relative to its radius, compared to most ordinary atomic matter. The term typically refers to very high-density objects such as

1852:; this means that the path of the Sun, as viewed from Earth, appears to move both above and below the celestial equator during the course of the year. 16654: 13144:

as observed from Earth, but can in principle be calculated with respect to the sky as observed from any body. It is related to but distinct from the

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2. An astronomical event during which a celestial body or object passes visibly across the face of a much larger body. An example is the

11195:(or any other distant luminous object) as viewed through a medium, such as the Earth's atmosphere, caused by the passing of light through layers of 13272:

on the spectra of other stars. For example, water vapor in the atmosphere creates significant telluric absorption bands at wavelengths above 6800

11119:

A broken arc of illuminations seen at the limb of very young or very old lunar crescents. The visual similarity to the moments before and after a

16661: 11951:, as viewed from a given location on the Earth's surface. Because the duration of this interval changes during the Earth's orbit around the Sun, 8846:

A measure of the resistance of a medium to the radiative transmission of energy. Within a star, it is an important factor in determining whether

7534:

within an astronomical object. Note that this definition includes elements that are not traditionally considered metallic by chemical convention.

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that display pulsation frequencies of two different classes of variables. An example are variables displaying characteristic frequencies of both

1769:. The focus remains stationary as the telescope is re-oriented, which is advantageous for the stable mounting of heavy spectroscopic instruments. 1587:. It depicts a starting condition of extremely high density and temperature, followed by an ongoing expansion that led to the current conditions. 10334:

The rate of angular motion of an object over an interval of time, usually years. For stars, this is typically given in milliarcseconds per year.

16759: 10433:

that emits a beam of electromagnetic radiation. This beam is observed only when it is pointing toward Earth, making the object appear to pulse.

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telescopes to produce reference markers in photographs of distant stars, allowing precise and convenient measurement of astrometric positions.

6990:

are caused by the visible side of the Moon being alternately illuminated by sunlight and immersed in shadow during its orbit around the Earth.

16918: 15058:

Rufener, F.; Bartholdi, P. (June 1982), "List of 333 variable, microvariable or suspected variable stars detected in the Geneva photometry",

11567:, measured as the time it takes for the Sun, as viewed from a particular point on the Earth's surface, to return to the same position in the 10603:. Positive values are used to indicate a receding object. An object such as a star can undergo changes in its radial velocity because of the 14325:

A band of light in the night sky, thought to be sunlight reflected from cometary dust concentrated in the plane of the zodiac, or ecliptic.

11424:, e.g. the Earth's orbital period around the Sun. The name "sidereal" implies that the object returns to the same position relative to the 482:

A measure of the brightness of a celestial body as seen by an observer on Earth, adjusted to the value it would have in the absence of the

15579: 13769:

of the ellipse. The true anomaly is one of three angular parameters that define a position along an orbital path, the other two being the

7885:, only one side of the Moon is ever visible from the Earth. Sunlight reflected from its surface makes the Moon appear very bright in the 14998:

The large scale structure of the universe; Proceedings of the Symposium, Tallinn, Estonian SSR, September 12-16, 1977. (A79-13511 03-90)

9253:, etc., or any combination thereof) exist in some definite mathematical relationship with each other. Most commonly, the term refers to 15995: 11305:

system or star–planet system. When the distance between the orbiting bodies is unknown, the semi-major axis may be given as an angle.

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that had the visual appearance of a galaxy with a particularly bright, star-like nucleus. As a group, they are intermediate between

241:. The material is acquired from a source external to the central object, and friction causes it to spiral inward towards the object. 5692:

allows its age to be estimated. Stars of similar types are also found grouped together in specific regions of the chart, including

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Silaj, J.; Jones, C. E.; Tycner, C.; Sigut, T. A. A.; Smith, A. D. (March 2010), "A Systematic Study of Hα Profiles of Be Stars",

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around a planet. Though the smaller body is often said to orbit the larger body itself, both bodies actually follow approximately

8777:

is hidden by another, nearer body or object that passes between it and the observer, thereby blocking the first object from view.

1124:. Though the terms astronomical "object" and astronomical "body" are often used interchangeably, there are technical distinctions. 16373: 14941:

Forbes, John C.; Loeb, Abraham (February 2019), "On the Existence of Brown Dwarfs More Massive than the Hydrogen Burning Limit",

13386:. Stars belonging to this population generally follow orbits that lie close to this plane. This is in contrast to members of the 3748: 3454: 11591:. The length of the solar day is also not constant, but rather changes over the course of the year because the Earth's orbit is 8603:

values over time, showing how observed data differ from theoretical values which have been calculated according to a particular

17023: 14502: 8188:. Thus, where the zenith is directly above an observer, the nadir is underfoot. The zenith and nadir form the two poles of the 7550:

that has survived its passage through the atmosphere to reach the surface of a planet or moon, usually ranging in size from 50

5829:, the hour angle is one of many ways commonly used to specify the longitudinal position of an object upon the celestial sphere. 3963: 1220:

around the Sun, the astronomical unit is now more rigidly defined as exactly 149,597,870.7 kilometres (92,956,000 miles; 4.8481

650:(in geocentric and heliocentric orbits) or at which the orbiting object moves away from the observer (in orbits outside of the 2550:

or has fallen on Earth, generally composed of fine particles of solid matter far smaller than those found in terrestrial dust.

16946: 16941: 15503: 14393: 6176:

An effect produced by the incremental absorption and scattering of electromagnetic energy from interstellar matter, known as

3017:(in geocentric and heliocentric orbits) or at which the orbiting object moves toward the observer (in orbits outside of the 14415: 8830:

and a spherical outer Oort cloud. The outer limit of the Oort cloud is often considered the cosmographical boundary of the

2855:

are measured in positive degrees from 0° to 90°, while coordinates to the south are measured in negative degrees. See also

13132:. Synodic period is most commonly used to indicate the elapsed time between a given body's consecutive appearances in the 3531:

shape and a smooth, nearly featureless appearance. They are one of three main morphological classes of galaxy, along with

16863: 16818: 12153:

instruments are often placed in orbit, above the atmosphere, where detection of all parts of the spectrum is uninhibited.

9337:, or the instantaneous speed at a particular point in the orbit. Maximum instantaneous orbital speed typically occurs at 7612:. Detecting microvariability typically requires a sufficient number of observations to rule out random error as a source. 14466:

Noyes, R. W.; et al. (April 15, 1984), "Rotation, convection, and magnetic activity in lower main-sequence stars",

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and gases which are stripped from gas clouds and star clusters because of interaction with the gravitational field of a

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that originated in outer space and survived its passage through the atmosphere to reach the surface of a planet or moon.

6696:

A unit of length used to express astronomical distances that is equivalent to the distance that an object moving at the

2599:. Collisions of cosmic rays with the Earth's atmosphere can produce dramatic effects both in the air and on the surface. 1370:. The phenomenon is similar to but much larger in magnitude than other changes in the alignment of Earth's axis such as 17048: 16988: 16961: 15649: 15622: 15564: 15464: 15409: 15310: 15096: 14766: 14636: 14556: 14423: 9976:, with the aim of understanding their formation, composition, topography, dynamics, and interactions with other bodies. 15163:

Miller, J. S. (December 1981), "The galaxy components of BL Lacertae objects, N systems, and quasi-stellar objects.",

11829:

equals 2/3), or approximately 695,700 kilometres (432,300 mi). It is commonly used to express the radii of other

10095:

whose internal strength is dominated by self-gravity and whose orbital dynamics are not significantly affected by gas

10089:

Any solid object (generally larger than 1 kilometre (0.62 mi) in diameter) that arises during the formation of a

5273:

such that, to an observer on Earth's surface, the orbiting object appears motionless, in a fixed position in the sky.

16913: 16873: 16798: 15733: 15283: 15035: 14841: 14729: 14450: 12588: 1993: 9617:

The complex motion of an astronomical body that is subject to forces other than the gravitational attraction of its

1949:, i.e. the two points in the sky that are directly overhead the terrestrial North and South Poles, around which all 17084: 16983: 16901: 16896: 16492: 14350: 12194:

as they would appear from a particular date, time, and location on Earth. It relies on the mathematical methods of

11228: 9771:

An imaginary plane that is perpendicular to the line of sight. Typically this is used as a reference plane for the

7651:

that cannot be individually distinguished by the naked eye. The Milky Way Galaxy has a diameter of 100,000–200,000

6125: 14896:

Sánchez Arias, J. P.; et al. (January 2017), "Asteroseismology of hybrid δ Scuti-γ Doradus pulsating stars",

8417:, but with a radius of only 12 km (7.5 mi), making them among the densest known objects in the universe. 7023:. A MACHO is a body that emits little or no radiation and drifts through interstellar space unassociated with any 5741:. It is computed with respect to the next most gravitationally attractive object, such as the nearest star or the 2157:. Schröder et al. (2009) divide solar-type stars into four groups depending on their activity index: very active ( 1458:

An angular measurement of an object's orientation along the horizon of the observer, relative to the direction of

16310: 14700: 14340: 13120:

The time it takes for a body visible from another body (often the Earth) to complete a cycle with respect to the

12969:, including that produced by the effects of rotation. It is typically expressed in units of acceleration such as 11340:

of the Earth begins to tilt away from the Sun, and typically occurs on or near September 22 each year. It is the

11209:, since light rays near the horizon must travel longer paths through the atmosphere before reaching the observer. 8411:

with no electrical charge. Typically, neutron stars have a mass between about 1.35 and 2.0 times the mass of the

6809: 5632: 4847:. Galaxies may contain hundreds of billions of stars and are categorized according to their visual morphology as 4187:. These field stars are important to identify in order to prevent them from contaminating the results of a study. 3892:

is equal to zero. It is a function of the mass of the body and of the distance between the object and the body's

13950:

Universe, whose spatial extent is unknown because it is not directly measurable; this is distinguished from the

10599:

The velocity of an object along the line of sight to the observer, which in astronomy is usually determined via

5308:, such that the orbiting object appears to return to exactly the same position in the sky after a period of one 1354:

over a cycle of approximately 25,772 years, which is caused predominantly by the gravitational influence of the

351:

A large area on the surface of a reflecting object that shows a significant contrast in brightness or darkness (

17074: 15988: 15866: 15537: 15257: 6397: 3889: 15208:

The Light-Time Effect in Astrophysics, Proceedings of ASP Conference Series, held in Brussels 19-22 July 2004.

11265:

The angle at the position of an observer subtended by the equatorial radius of the Sun, the Moon, or a planet.

3424:, the Sun's path appears to intersect the celestial equator, though the two planes are never in fact coplanar. 1181:. Many of these symbols were commonly used historically, though in the modern era they are usually limited to 17043: 17033: 16858: 16853: 16596: 14109:

process with its constituent atoms, so the object's energy output normally comes from radiative cooling. See

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which are left over from the formation process. There is no precise distinction between a planetesimal and a

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in the same time it takes Neptune to complete three. Resonance may act on any time scale, from short-term to

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through the coordinated observation and interpretation of four disparate classes of "messenger" signals with

6875: 6364: 2267: 2809:

being emitted from the star system, as the orbiting debris re-radiates the star's energy into space as heat.

1411:

The angle between an object's rotational axis and its orbital axis, or, equivalently, the angle between its

16908: 16868: 16262: 15025: 12055:

is either 90 degrees or 270 degrees. The solstices occur on or near June 20 and December 21 each year. The

10320:. The actual separation of the two objects depends on the angle of the line between the two objects to the 10162: 5446: 3735: 2251: 15802:

Yuan, Feng; Narayan, Ramesh (September 2004), "On the Nature of X-Ray-Bright, Optically Normal Galaxies",

7204:

of the Earth begins to tilt toward the Sun, and typically occurs on or near March 20 each year. It is the

3348:. Hence, the position of the Sun as viewed from the Earth defines the intersection of this plane with the 2587:

and atomic nuclei which move through space at nearly the speed of light, and which may originate from the

16956: 16951: 16848: 16833: 13154:) and the body from which it is being observed (e.g. Earth) are independently orbiting a third body (the 12594:

1. The region within the volume of a star that transports energy from the stellar core to the

11019: 10804: 10279: 10215: 7700: 7002: 4580: 2554: 1467: 11647:

location and on the apparent sizes of the solar and lunar disks in the sky, an eclipse may appear to be

10609:

of another body, or because of radial pulsations of its surface. The latter, for example, occurs with a

8574:

which results from the combined effects of small, short-term variations. Nutation is distinguished from

7580:, usually weighing less than one gram. If it survives to reach a planetary surface, it is then termed a 1955:

appear to revolve during the course of a day. The celestial poles form the north and south poles of the

17008: 16978: 16739: 16647: 16429: 16221: 15725: 14345: 14189: 14102: 12954: 12252: 6730:-scale distances in non-specialist publications, the unit of length most commonly used in professional 5524:

from these hot stars ionize gas in the surrounding environment, and the nebular gas shines brightly in

4595: 3429: 2812: 2630: 2196: 15749:

Pace, G.; et al. (April 2003), "The Wilson-Bappu effect: A tool to determine stellar distances",

15480: 13086:. As it does on Earth, an object's synodic day may change slightly in duration over the course of the 5279:

are often placed in geostationary orbit so that antennas on Earth do not have to rotate to track them.

3441:

commonly used to specify the apparent positions, orbits, and axial orientations of objects within the

3078:

is so distant that the object is only moderately or weakly affected by the gravitational influence of

1299:(rather than the positions or motions of objects in space, which is more specifically the emphasis of 16668: 16485: 16450: 16443: 16290: 15981: 15532:, Space Telescope Science Institute Symposium, vol. 12, Cambridge University Press, p. 97, 13791: 12970: 12132: 11612:(averaged over the Earth's orbital period) is currently equal to 86,400 seconds, or exactly 24 hours. 11168: 10651: 10321: 9903: 9229:

bodies exert regular, periodic gravitational influences on each other such that one or more of their

8103: 8078: 4871:

are between 1,000 and 3,000 parsecs (3,300 and 9,800 ly) in diameter though some, including the

3971: 3865:

the equator, and the durations of day and night are approximately equal all over the planet. Compare

3508: 15665:

Heller, R.; et al. (April 2011), "Tidal obliquity evolution of potentially habitable planets",

13684:, which was visible from Earth in 2004 and 2012. Because a transit results in a decrease in the net 9288:, and often leads to either long-term stabilization of the orbits or their eventual destabilization. 7907:

is often used specifically to describe the orbit, gravity, and other properties of the Earth's Moon.

7839:

A dimensionless quantity that characterizes the radial distribution of mass inside a planet or moon.

3670:

A moment in time used as a reference point for some time-varying astronomical quantity, such as the

792:; and bodies similar to asteroids in size and composition but which lie beyond Jupiter are known as 536:. The term may also be used to refer to the value of the distance rather than the point itself. All 16843: 16813: 16691: 16457: 15112: 13538: 10836:

orbit, a satellite (red) orbits in the direction opposite the rotation of its primary (blue/black).

10563: 9611: 9411:, characterized generally by extremely low densities of particles, extremely low temperatures, and 7824: 5525: 5257:, which maintains a constant altitude of 35,786 kilometres (22,236 mi) directly above Earth's 4431: 2216: 377:. The spectrum of the Am stars shows abnormal enhancements and deficiencies of certain metals. See 368: 265: 15641:

Dynamics of the Milky Way: Tidal Streams and Extended Distribution Functions for the Galactic Disc

15138: 14548:

Astronomical Applications of Astrometry: Ten Years of Exploitation of the Hipparcos Satellite Data

9421:

is intergalactic space, and even galaxies and star systems consist almost entirely of empty space.

6978: 5419:, which can bend passing light from a distant source by a noticeable degree. The effect, known as 16998: 16973: 16808: 16803: 16552: 16338: 16197: 16176: 16135: 16099: 16067: 15527: 14258: 14123: 13716: 13417:

The transfer of momentum between an astronomical body and an orbiting satellite as the result of

12871: 12711: 12078: 11533: 11142: 10797:

Orbital or rotational motion of an object in the direction opposite the rotation of the object's

10460: 10203:

refers to a steady change in the orientation of an orbit, such as the precession in the orbit of

9866: 9799: 9650: 9587: 8725: 7873:, completing a full orbit every 27.3 days. The Moon's gravitational influence is responsible for 7639:. The name describes the galaxy's appearance from the Earth: a hazy band of light visible in the 7134: 6356: 5944: 4223:

lower (i.e. brighter) than 1.50. There are 22 stars that are classified as first magnitude stars.

4191: 4107: 3992: 2772:, at which it reaches its lowest point, nearly 12 hours later. When not otherwise qualified, the 2377: 1565:

were generated in the early Universe, including the means by which baryons outnumber antibaryons.

762:. Asteroids are somewhat arbitrarily distinguished from many different types of similar objects: 389: 245: 15086: 10272:

Orbital or rotational motion of an object in the same direction as the rotation of the object's

10111:

during the process of planet formation, but is also sometimes used to refer to various types of

8457:, and more specifically when clear weather and low levels of ambient light permit visibility of 1088:

A type of naturally occurring physical entity, association, or structure that exists within the

17028: 17013: 16605: 16478: 16471: 16394: 16188: 15587: 14238: 14145:. This linear relation makes it useful for determining the distances of G, K, and M-type stars. 14014: 13876: 13798: 13643: 13265: 12657: 12556: 12527: 11288:. It is expressed in units of length and often used to give a physical dimension to a two-body 11200: 11146: 10467: 10449: 10388: 10181: 7992: 6170: 5884: 5589: 5398: 5394:

in having a much higher combined mass, with a typical lifespan extending for billions of years.

5188: 4532: 4267: 3956: 3610: 2825: 2517: 2286:

A term used to indicate that two or more stars share the same motion through space, within the

2236: 2106: 2063: 1683:. At rotational velocities beyond this point, the star begins to eject matter from its surface. 1054: 888: 15719: 15608: 15454: 14752: 14715: 14440: 11875:

and all of the objects that orbit it, either directly or indirectly, including the eight true

4147:. An increase in faculae as a result of a stellar cycle increases the star's total irradiance. 2167:

above −4.2), active (−4.2 to −4.75), inactive (−4.75 to −5.1), and very inactive (below −5.1).

2053:, and generally also have unstable orbits because they cross the orbits of one or more of the 39:. The field of astronomy features an extensive vocabulary and a significant amount of jargon. 16883: 16575: 16269: 16207: 16030: 15856: 15554: 15399: 15273: 14546: 14503:"Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo" 14409: 14355: 13348: 13269: 12475: 11500: 10944: 10696: 10060: 9672:

generally have low phase angles as seen from Earth, so they often appear as a slim crescent;

9499: 9379: 8556: 8421: 7331:

The measurement of positions of celestial objects based on observation of the times of their

7085: 6624: 4574:. It is approximately 8,200 parsecs (27,000 ly) away from Earth in the direction of the 4328: 3497: 3399:(grey) is defined by the Earth's orbit around the Sun, and is distinct from the plane of the 2478: 2303: 983:

The branch of astronomy that involves precise measurements of the positions and movements of

898: 546: 483: 15772: 15688: 15639: 15439: 15339: 15300: 15071: 14919: 14869:

Chebotarev, G. A. (April 1964), "Gravitational Spheres of the Major Planets, Moon and Sun",

14521: 14129:

A correlation between the width of the singly ionized calcium K-line (Ca II K) at 3933

13821:

width. It can be used to estimate the distance of the galaxy, and hence forms a rung on the

13435:

orbit will gradually recede from its primary while slowing the rotation rate of both bodies.

11008:

in which they formed, or otherwise have never been gravitationally bound to any star system.

10304:

The observed physical separation between two astronomical objects, as determined from their

5823:, and the plane containing Earth's rotational axis and the object of interest. Analogous to 1100:, consisting perhaps of multiple bodies or even other objects with substructures, such as a 17053: 17038: 17003: 16993: 16838: 16567: 16499: 16317: 16255: 16046: 16023: 16016: 15920: 15821: 15768: 15684: 15614: 15435: 15362: 15335: 15211: 15172: 15067: 15001: 14960: 14915: 14878: 14660: 14591: 14517: 14475: 14335: 13653: 13582:

in which the three bodies all differ greatly in mass. The parameter is calculated from the

13276:. These features need to be corrected for in order to more accurately measure the spectrum. 12308: 12096: 11101: 10610: 10600: 10400: 9807: 9513: 8965: 8870: 8860:

A gravitationally bound group of up to one thousand stars that formed together in the same

8535: 8062:

which travel together through space. Although the members were formed together in the same

7305: 6676: 5880: 5283: 4638:, usually home to a very dense concentration of stars and gas. It almost always includes a 4298: 4227: 4213: 3297: 2359: 1846:. Note that the Earth's rotational axis is not perpendicular to the ecliptic but rather is 1766: 1463: 1296: 706: 593: 15886: 13310:

slows to subsonic speeds (relative to the Sun) as a result of interactions with the local

6975:. The phase of the Moon at any particular time appears the same from every point on Earth. 6085:, both appear to travel with the Sun across the sky. This is in contrast to the so-called 2427: 321: 8: 17018: 16968: 16878: 16828: 16698: 16640: 16436: 16387: 16283: 16230: 16053: 15861:, Astronomy and Astrophysics Library, Springer Science & Business Media, p. 39, 14721: 14007: 13618: 12730: 12570: 12167: 11686: 11203:

caused by small-scale fluctuations in air density, and are much more pronounced near the

10372: 10224: 9741: 9031: 8755:, which is concerned with calculating the measurable implications of astronomical models. 8716: 6135: 6034: 5270: 5227: 5107: 5004: 4738: 4502: 4126: 3896:. An object which has achieved escape velocity is neither on the surface nor in a closed 2211:

A numeric value that is used to compare the brightness of a star measured from different

1857: 1622: 1345: 1128: 1073: 658: 325: 36: 32: 16751: 15825: 15366: 15215: 15176: 15005: 14964: 14882: 14664: 14595: 14572:

Townsend, R. H. D.; et al. (May 2004), "Be-star rotation: how close to critical?",

14479: 13264:

with nearly featureless continuum spectra that can be used to correct for the effect of

11470:, i.e. the time interval between two successive returns of the fixed stars to the local 6166:, but is enhanced by traces of other elements contributed by matter expelled from stars. 5426: 3743: 3597:

A relatively small body (such as a planet) orbiting a larger one (such as a star) in an

3437: 656:). The position of the ascending node with respect to a reference direction, called the 17079: 16727: 16626: 16331: 16301: 16248: 16183: 16131: 16106: 15837: 15811: 15784: 15758: 15700: 15674: 15380: 15188: 14978: 14950: 14905: 14678: 14609: 14581: 14312: 14037: 13946:

that describe them. When not otherwise qualified, "the Universe" usually refers to the

13578: 13402: 13320: 13198: 12502: 12389:

system. In the broadest sense, very large groups of stars bound by gravitation such as

12195: 11232: 11227:

Any change in movement that happens over a very long time period. Examples include the

10305: 10208: 9708: 9690: 8958: 8607:. It is often used as a diagnostic tool to determine the accuracy of the model. With a 8491: 8408: 8107: 7817: 7676: 6323:

positions of stars having the same age but differing masses. This is in contrast to an

6099: 5463: 5407: 5184: 4786: 4475: 4220: 3906: 3660:

at various dates and times. Modern ephemerides are often provided by computer software.

3617: 2171: 1907: 947: 467: 305: 183: 14673: 12884:

which possess masses ranging from hundreds of thousands to many billions of times the

12140: 10849: 3493:

to the ecliptic. It may be implemented in either spherical or rectangular coordinates.

3090: 2841: 1957: 1797: 1625:, a type of optical illusion which is entirely distinct from true binary star systems. 31:, their sub-disciplines, and related fields. Astronomy is concerned with the study of 16633: 16619: 16418: 16403: 16380: 16324: 16092: 15862: 15729: 15704: 15645: 15618: 15560: 15533: 15460: 15405: 15384: 15375: 15306: 15279: 15253: 15249: 15192: 15092: 15031: 14982: 14762: 14725: 14682: 14632: 14604: 14552: 14446: 14419: 14389: 14247: 14234:

that is directly overhead from the perspective of a particular location on the Earth.

14116: 13943: 13280: 13235:(i.e. in the tangent plane). This component can be computed from the body's observed 12991: 12759: 12619: 12260: 11585:, which results in the solar day being on average about four minutes longer than the 11309: 10791: 10685: 10404: 10195: 9943: 9217: 9059: 8271: 8222: 7843: 7766: 7129: 6672: 6586: 6340: 6313: 6305: 5894: 5889: 5876: 5747:. Satellites moving outside this radius tend to be perturbed away from the main body. 4427: 4318: 4257: 4163:

that does not belong to a larger cluster of galaxies and is gravitationally isolated.

4053: 4019: 3914: 3722: 3672: 3664: 3515: 3368: 2959: 2668: 2664: 1773: 1727: 1680: 1676: 1529:

of each body participating in the system; its location is strongly influenced by the

1382: 1199: 999: 854:

to distinguish it from other asteroid populations in other parts of the Solar System.

496:

The closest approach of one celestial object to another, as viewed from a third body.

15841: 15788: 14613: 13338:

from its dark side. The line moves as the object rotates with respect to its parent

13204:

The straight-line configuration of three celestial bodies in a gravitational system.

12051: 10491:

as viewed from the Earth. The term is used especially to describe the position of a

10475: 9812: 7606:, in which the amplitude of the fluctuations amounts to just a few thousandths of a 7121:

which form a continuous and distinctive band on plots of stellar temperature versus

5567: 4801:. Galactocentric distance may also refer to a galaxy's distance from another galaxy. 4272: 3924:

of a particular mass and composition is expected to follow during the course of its

3831: 2401: 2229:

A relatively small, icy body that displays extended features when it approaches the

1807:, this plane is currently inclined at an angle of 23.44 degrees with respect to the 1715: 1014:

A type of naturally occurring physical entity, association, or structure within the

16538: 16517: 16352: 16345: 15829: 15776: 15692: 15370: 15180: 14968: 14923: 14668: 14599: 14525: 14483: 13860: 13814: 13766: 13675: 13461: 12693: 12668: 12579: 12423: 12294: 12256: 12217: 11765: 11129: 11012: 10771: 10677: 10453: 10204: 9980: 9913: 9724: 9354: 9192: 9170: 8987: 8840: 8604: 8159: 6545: 6246: 6224: 6192: 6059: 5960: 5808: 5758: 5550: 5423:, can make background objects appear to an observer to take on a ring or arc shape. 5358: 5171: 5114: 4613: 3712: 3547: 3339: 3335: 2486: 2450: 2135: 1965: 1520: 1443: 1367: 1320: 1254: 1217: 41: 15956: 15904: 15696: 14927: 14530: 11969:

were employed by astronomers as time reckoning systems before the introduction of

8743:

and other astronomical instruments. It is concerned with recording data about the

6374:. It is therefore widely used as the basis for defining the standard astronomical 5807:

that passes through the celestial object; or, equivalently, the angle between the

16684: 16359: 16276: 16214: 16169: 16113: 15780: 15206:

Sterken, C. (July 2005), Sterken, C. (ed.), "The O-C Diagram: Basic Procedures",

15041: 14182: 14177: 14017:

of velocities about the mean velocity for a group of objects, such as stars in a

12946: 12830: 12702: 12184: 11889: 11406: 11269: 11046: 10910: 10841: 10644: 10636: 10617: 10593: 10558: 10540: 10257: 10113: 9920: 8847: 8672: 8655: 8483: 8280: 8263: 7804: 7708: 7378: 7155: 6478: 6052: 5454: 5118: 5030: 4997: 4993: 4981: 4652: 4650:

in a compact region than its surroundings. This excess luminosity is known as an

4640: 4604: 4564: 4539: 4494: 4439: 3939: 3877: 3859:

each year. On the day of an equinox, the center of the visible Sun appears to be

3582: 3483: 3280: 3104: 3035: 2990: 2952: 2920: 2893: 2806: 2287: 2264: 2240: 2078: 2001: 1743: 1344:. The term often refers in particular to the gradual shift in the orientation of 830: 764: 289: 16:

List of definitions of terms and concepts commonly used in the study of astronomy

15404:, Cambridge Astrophysics, vol. 34, Cambridge University Press, p. 25, 15210:, vol. 335, San Francisco: Astronomical Society of the Pacific, p. 3, 14081: 13823: 13429:

for both bodies as well as modification of their mutual orbit. A satellite in a

12087: 11945:, i.e. the time interval between two successive returns of the Sun to the local 10780: 8629: 8481:. The night sky remains a fundamental setting for both amateur and professional 6760: 6681: 5125: 5059:

explosions of high-mass stars. Short GRBs may also result from the collision of

4763: 4547: 3805:

Either of the two precise times of year when the imaginary plane of the Earth's

3084: 2982: 1212:

or secondarily between the Earth and distant stars. Originally conceived as the

1191: 16531: 16464: 16366: 15088:

Astronomy for beginners : all you need to know to get started in astronomy

14973: 14319: 14262: 14106: 14030: 14029:. This value can be used to derive the combined mass of the group by using the 13939: 13840: 13691: 13388: 13114: 12804: 12781: 12664: 12335: 12158: 12119: 11994: 11655: 11221: 11159: 10980: 10096: 9889: 9844: 9686:

usually have high phase angles, so that little of the shadowed side is visible.

9643: 9120: 8751: 8708: 8615: 8546: 8151: 7816:

in which the prevailing physical conditions allow molecules to form, including

7568: 7538: 7359: 7138: 6746: 6650: 6590: 6255: 5674:

for temperature. Single stars of known mass and composition follow predictable

5646: 4964: 4881: 3893: 3885: 3825: 3475:, and a right-handed convention. This system is convenient because most of the 3394: 3122: 2867: 2799:

of dust and debris orbiting its host star. It is created by collisions between

2443: 1925: 1700: 1510: 1213: 623: 345: 217: 13094: 12896:, where they can have a profound effect upon the evolution of the surrounding 12751: 10916: 10747: 9571: 9237: 7516:. This makes many meteor showers predictable events, as they recur every year. 7440:, usually as a long streak of light produced when such an object is heated to 6616: 6291:. Irregular moons are thought to be captured from other orbits, as opposed to 6275: 5905:

A critical mass below which an astronomical object cannot sustain its surface

5275: 5253: 5018: 4345: 4290: 3650: 3570: 3306: 2671:. At this rotation rate, mass can be readily lost from the equator, forming a 2368: 2084: 2037: 1899: 1762: 1136: 968: 794: 451: 17068: 16589: 14130: 14076: 14000: 13980: 13952: 13818: 13725: 13633: 13602: 13448: 13312: 12965: 12776: 12725: 12437: 12208: 11953: 11826: 11712: 11682: 11649: 11616: 11480: 11440: 11259: 11121: 10741: 10701: 10659: 10640: 10631: 10579: 10352: 10328: 10167: 10101: 9923:

formed from a glowing shell of expanding plasma that has been ejected from a

9407: 9309: 9163: 9137: 9094: 8893: 8773: 8745: 8733: 8608: 8542:

A compact and dense concentration of stars located at the center of a galaxy.

8515: 8459: 8355: 8330: 8163: 8147: 8092: 8010: 7486: 7441: 7367: 7173: 7109: 7097: 7057: 7020: 6870: 6818: 6269: 6113: 6043: 5731: 5606: 5439: 5322: 4989: 4893:

bound together by gravity. Galaxy clusters are distinct from similarly named

4867: 4825: 4725: 4687: 4666: 4370: 4027: 3984:. Atmospheric extinction varies by the wavelength of the radiation, with the 3976: 3684: 3644: 3489: 3130: 2902: 2828:, and artist's impressions of the disks' orientations around their host stars 2706: 2409: 2385: 2143: 1985: 1875: 1583: 1435: 1301: 1279: 1240: 1090: 1046: 1016: 909: 802: 15045: 14135: 12596: 11185: 11052:

The time that an object takes to complete a single revolution about its own

10479:

that differ by 90 degrees as viewed from a third body, e.g. when a planet's

10052: 9291: 9203: 9112: 9088: 9051: 9022: 8509: 8336: 7812: 6894: 6836: 6472: 6348: 6325: 5676: 5658: 5466:

to collect observational data about astronomical objects and events such as

5433: 4911:. Galaxy groups and galaxy clusters can themselves cluster together to form 4492:, as opposed to everything outside of the Milky Way, which is the domain of 4011: 3946: 3387: 3356: 3013: 2875: 2795: 2746:. During each day, the Earth's rotation causes every astronomical object to 2673: 1154: 959:

where evidence for an unseen orbiting companion is revealed by its periodic

810: 768:

primarily composed of dust and ice instead of mineral and rock are known as

646: 197: 16545: 16524: 16142: 14849: 14200: 13852: 13771: 13734: 13696: 13530: 13472: 13294: 13225: 13164: 12959: 12932: 12821: 12745: 12737: 12649: 12353: 12114:. Instead, the evidence for the binarity comes from shifts observed in the 12017: 11907: 11857: 11848: 11799: 11669: 11360: 11326: 10998: 10951: 10887: 10859: 10831: 10729: 10721: 10705: 10316: 10291: 10127: 10083: 10028: 9966: 9789: 9479: 9412: 9299: 9181: 9068: 8911: 8854: 8822: 8767: 8564: 8527: 8391: 8334:

of indistinct nebulosity. In modern usage, the term typically refers to an

8302: 8239: 8041: 7957: 7932: 7869: 7852: 7774: 7758: 7726: 7296: 7224: 7215: 7190: 7011: 6570: 6508: 6406: 6319: 6281: 6263: 6227:

vector, and which may be regarded as the weighted average of all planetary

6066:. The name originated from the fact that these planets orbit closer to the 5851: 5840: 5791: 5682: 5330: 5292: 4972: 4921: 4849: 4400: 4343:

while traveling from north to south each year. It is directly opposite the

4339: 4306: 4288:

while traveling from south to north each year. It is directly opposite the

4284: 4151: 3926: 3855: 3813: 3771: 3765: 3727: 3539: 3465: 3407: 3374: 3259: 3230: 3195: 2976: 2851: 2680: 2469: 2327: 2310: 2092: 1893: 1829: 1780: 1758: 1695: 1662: 1555: 1377: 1334: 1263: 1096: 991: 927: 918: 902: 893: 884: 858: 614: 294: 14301: 14283: 14019: 13783: 13761: 13661: 13584: 13128: 13048: 12975: 12892: 12462: 12403: 12190: 11865: 11517: 11432: 11380: 11290: 11237: 11217:

Continuing, or changing in a non-periodic way, over a long period of time.

11060: 11054: 11004: 10986: 10899: 10691: 10368:

as they collide with each other and gradually coalesce into larger bodies.

10189: 9972: 9826:

is used in reference to a planet-like object that is not orbiting the Sun.

9759: 9753: 9729: 9637: 9463: 9438: 9431: 9231: 9009: 8979: 8917: 8570: 8178: 7281: 7239: 7025: 6842: 6796:, and which therefore represents the distance of the orbit's longest axis. 6792: 6610: 6219: 5939: 5813: 5785: 5779: 5743: 5537: 5415: 5378: 5201: 5151: 4944: 4861: 4843: 4522: 4312: 4251: 4205: 3998:

The branch of astronomy that studies objects and phenomena outside of the

3843: 3759: 3717: 3678: 3600: 3401: 3350: 2754: 2509: 2417: 1945: 1939: 1822: 1785: 1535: 1525: 1340: 1102: 664: 605:

by humans, often around the Earth but also around other bodies within the

585: 538: 16787: 16612: 15816: 15763: 14848:, U.S. Naval Observatory and H.M. Nautical Almanac Office, archived from 14586: 14208: 14097: 14089: 13995: 13959:

2. One of many hypothetical parallel universes which exist as

13614:

With reference to, or pertaining to, a point on the surface of the Earth.

13439: 13431: 13425: 13054: 13031: 13023: 13017: 12862: 12798: 12605: 12362: 12124: 12070: 12063: 12049:

as seen from Earth; or, equivalently, when the Sun's apparent geocentric

11959: 11839: 11785: 11703: 11661: 11605: 11557: 11368: 11249:

With reference to, or pertaining to, the geometric center of the Earth's

10925: 10867: 10816: 10735: 10669: 10575: 10506: 10493: 10338: 10149: 9936: 9699: 9674: 9664: 9517: 9484: 9402: 9386: 9243: 9155: 9106: 8862: 8827: 8759: 8521: 8504: 8064: 7717: 7682: 7660: 7520: 7383: 7164: 7016: 6943:: as the orbital positions of the Moon around Earth and Earth around the 6916: 6800: 6455: 6087: 5949: 5833: 5825: 5714: 5598: 5559:, i.e. the arithmetic mean position of all points within the approximate 5518: 5514: 5501: 5316: 5304: 5265: 5117:

of the Earth, i.e. the arithmetic mean position of all points within the

4954:, and galaxy groups and clusters can themselves cluster together to form 4950: 4819: 4791: 4705: 4510: 4406: 4353: 3985: 3981: 3247: 3172: 3113: 2858: 2833: 2787: 2689: 2526: 2395: 2351: 2298: 2205: 2147: 2013: 1687: 1591: 1292: 1246: 880: 671: 315: 155: 14501:

Schröder, C.; Reiners, Ansgar; Schmitt, Jürgen H. M. M. (January 2009),

14289: 14141: 13846: 13590: 13382: 13146: 13088: 13070:). The synodic day may be described as the time between two consecutive 13011: 11971: 11923: 11691: 11448: 11414: 11199:

in the medium. Most terrestrial scintillation effects are the result of

10763: 10552: 10099:. The term is most commonly applied to small bodies thought to exist in 9861: 9747: 9333: 9259: 9100: 8033: 7762:

is not a minor planet because it orbits another body instead of the Sun.

7582: 7418: 7269: 7263: 7245: 6830: 6698: 5845: 5298: 5248: 4143: 3837: 3777: 3605:, with the larger body located at one of the focal points of the ellipse 3576: 3471: 3288: 3154: 3096: 3026: 2748: 2259: 2031: 1425: 1165: 573: 514: 331: 16582: 16559: 16039: 15459:, Oxford Quick Reference Online (3 ed.), Oxford University Press, 14758: 14204: 13809: 13626: 13456: 13359: 13237: 12847: 12467: 12255:

of an object in a vacuum near the surface of the Earth, as a result of

12057: 11979: 11965: 11915: 11721: 11351: 11337: 11196: 11096:

or other localized activity across the line of sight. Examples include

11037: 10664: 10567: 10408: 9076: 9045: 9016: 8793: 8785: 8779: 8126: 8068:, they have since moved too far apart to be gravitationally bound as a 7881: 7696: 7624: 7596: 7555: 7551: 7504:. These are produced by debris left over from a larger body, such as a 7201: 7142: 6951: 6850: 6758:), where the center part of the disk appears brighter than the edge or 6689: 6520: 6441: 6370: 6237: 6229: 6073: 5771: 5694: 5670: 5531: 5468: 5390: 5061: 4956: 4913: 4907: 4901: 4855: 4576: 4528: 4452: 4422: 4414: 4324: 4263: 4245: 3967: 3849: 3533: 3504: 3238: 3234: 3218: 3204: 3056: 2736: 2573: 2461: 2425:, while the modern demarcation of their borders was established by the 2390: 2292: 2244: 2151: 2139: 2019: 1836: 1709: 1704: 1637: 1629: 1503: 1459: 1419: 1396: 1309: 1284: 977: 955: 726: 268:

with characteristics indicating that the luminosity is not produced by

169: 163: 14025: 13777: 13596: 13466: 13082: 12784:

of hydrogen nuclei can be sustained (equivalent to approximately 0.08

12685: 12643: 12391: 12327: 12148: 11883: 11773: 11593: 11587: 11466: 11420: 11295: 11072: 10905: 10873:

A disk- or ring-shaped accumulation of various solid material such as

10605: 10423: 10364: 10165:

of the body being orbited during each revolution. It therefore has an

10161:

in which the orbiting object passes directly over or nearly over both

10141: 10135: 10046: 10022: 9895: 9883: 9818: 9631: 9461:

A unit of length defined as the distance at which a star would show a

9374: 9362: 9265: 9209: 9149: 8832: 8810: 8678: 8399: 8366: 8257: 8070: 7983: 7965: 7950: 7944: 7899: 7795: 7780: 7635: 7275: 7049: 7037: 6939: 6526: 6502: 6447: 6293: 6026: 5982: 5861:

but additionally taking into account the terrain and the depth to the

5624: 5310: 5099: 5077: 4895: 4711: 4481:

The branch of astronomy that studies objects and phenomena within the

4382: 4183: 4137: 4091: 4076: 4043:

or any objects larger than a star or the Solar System itself, such as

4033: 3690: 3564: 3443: 3362: 3068: 3062: 3019: 3007: 2970: 2932: 2914: 2881: 2879:

formed from gas ejected from a central star that now follows a nearly

2801: 2595: 2339: 2111: 2055: 1208: 1148: 1108: 961: 842: 816: 788: 748: 742: 652: 640: 607: 16677: 16004: 15000:, vol. 79, Dordrecht, D. Reidel Publishing Co., pp. 51–60, 14789:"Distance & Speed Of Sun's Orbit Around Galactic Centre Measured" 13960: 13702: 13464:

between an astronomical body and its gravitational partner. When the

13419: 13368: 13288: 13245: 13172: 13122: 13066: 12938: 12906: 12792: 12611: 12494: 12385: 12303: 12188:

which is used to locate the positions of astronomical objects on the

12108:

system where the individual components have not been resolved with a

12104: 11941: 11821: 11677: 11624: 11581: 11551: 11543: 11505: 11454: 11426: 11374: 11301: 11066: 10939: 10933: 10875: 10854: 10809: 10457: 10429: 10381: 10310: 10284: 10193:. For the Earth in particular, this phenomenon is referred to as the 10119: 10107: 10010: 9773: 9735: 9524: 9468: 9249: 8637: 8444: 8431: 8364:

that could not be resolved into their individual components, such as

8342: 8198: 7616: 7560: 7464: 7448: 7102: 7092: 7043: 6985: 6969:; when the illuminated portion is becoming smaller, it is said to be 6704: 6659: 6436: 5974: 5919: 5803: 5706: 5688: 5664: 5575: 5474: 5459: 5179: 5069: 5043: 5038: 5023: 4985: 4837: 4831: 4781: 4733: 4584: 4178: 4121: 3636: 3528: 3265: 3253: 3187: 2964: 2819: 2623: 2603: 2580: 2546: 2503: 2422: 2333: 2212: 2025: 1979: 1951: 1816: 1720: 1617: 1599: 1513:

about which any two or more bodies of a gravitationally bound system

1494: 1274: 1232: 1186: 875: 518:, one of the two extreme points of distance between the body and its 380: 373: 28: 24: 13965: 13803: 13686: 13558:

A measure of the orbital motion of a relatively small body (e.g. an

13524: 13460:

such that, over the course of an orbit, there is no net transfer of

13306: 13100: 12914: 12886: 12880: 12786: 12562: 12560:

scheme is a two-dimensional classification based on temperature and

12383:

that orbit each other, bound by gravitational attraction, such as a

12321: 12200: 11599: 11402:, which instead reckons time based on the Sun's position in the sky. 11324:

The precise time of year on Earth when the Sun appears to cross the

11086: 11024: 10546: 10513: 10481: 10249: 9929:

star late in its life. The name derives from their resemblance to a

9658: 9473: 9327: 8923: 8712:

when estimating the shape and characteristics of the object's orbit.

8646: 8576: 8360: 8314: 8118: 8098: 7653: 7602: 7472: 7436: 7257: 7188:

The precise time of year on Earth when the Sun appears to cross the

7123: 7065: 7031: 6732: 6382: 6213: 6178: 5913: 5907: 5737: 5640: 5612: 5480: 5438:, distorting the light from a much more distant blue galaxy into an 5350: 5344: 5219: 5213: 4646: 4570: 3932: 3835:

is either 0 degrees or 180 degrees. The two equinoxes, known as the

3725:. The plane of the Earth's terrestrial equator is the basis for the 3413: 3380: 3074: 2345: 2007: 1848: 1803: 1707:

in its core, with the latter being a characteristic of stars on the

1611: 1487: 1328: 404: 310: 260: 237: 209: 175: 15833: 15184: 14955: 14910: 14487: 13898: 13831: 13755: 13510: 13394: 13376: 13273: 13220: 13140: 13106: 12920: 12851: 12719: 12456: 12312: 12290: 12115: 12110: 12031: 11990: 11751: 11524: 11511: 11398: 11151: 11092: 10712: 10625: 10346: 10040: 9925: 9339: 8739: 8380: 8347: 8086: 7974: 7887: 7689: 7641: 7608: 7576: 7546: 7527: 7500: 7478: 7412: 7251: 6888: 6780: 6432: 6159: 6118: 6107: 6077: 6003: 5987: 5955: 5863: 5735:

within which its gravitational attraction dominates the motions of

5700: 5560: 5384: 5207: 5157: 5133: 5082: 5055: 5049: 5037:

A cataclysmic event that generates a brief but intense outburst of

5012: 4873: 4797: 4749: 4717: 4588: 4553: 4516: 4483: 4444: 4376: 4219:

A term used to classify the brightest stars in the night sky, with

4199: 4000: 3705:

The imaginary line on a gravitationally rounded spheroid such as a

3315: 3160: 2926: 2846: 2776:

typically refers to the time at which the upper culmination occurs.

1865: 1795:. On Earth, the plane of the celestial equator is the basis of the 1577: 1569: 1388: 1206:

A unit of length used primarily for measuring distances within the

1177: 1171: 782: 776: 734: 720: 579: 526: 428: 413: 15938: 15679: 13969:, which itself comprises all of space and time and their contents. 13759:

and the current position of an orbiting body as it moves along an

13667: 13560: 13231: 12679: 12550: 11947: 11895: 11575: 11472: 10824: 10034: 9602: 9548: 9417: 9378:

were absent, i.e. the orbit that coincides with the instantaneous

9197: 8983:, the eccentricity ranges from greater than zero to less than one. 8684: 8286: 8112: 7694:

is visible in dark skies on clear nights, in the direction of the

7430: 7381:

between 1771 and 1781. The Messier catalogue includes most of the

7349:

distance at those times, with the intention of obtaining accurate

7339: 7105:, although this can vary depending on sky conditions and eyesight. 6786: 6484: 6184: 6012: 5911:

through nuclear fusion. This mass limit, equal to about 7% of the

5857: 5797: 5486: 4938: 3868: 3711:

that represents the intersection of the spheroid's surface with a

3459: 2742: 2635: 2611: 2434: 2043: 1916: 1842: 1809: 1466:

above the horizon, it defines an object's current position in the

1423:. Axial tilt usually does not change considerably during a single 1372: 1350: 1250:, the origins of those objects and phenomena, and their evolution. 1160: 1040: 836: 583:, measured in the direction of motion. It is one of six canonical 532: 16783: 15326:

Hut, P. (June 1981), "Tidal evolution in close binary systems.",

13708: 13478: 13151: 13071: 13060: 13005: 12856: 12298: 11285: 11205: 11030: 10881: 10799: 10757: 10274: 10173: 9992: 9987: 9803: 9683: 9619: 9557: 9541: 9368: 9284: 9273: 9187: 8953: 8888: 8702: 8580:, which is a similar but longer-term change in axial orientation. 8454: 8404: 8358:. Historically, it was also used to refer to extended sources of 8190: 8027: 7911: 7787: 7333: 6582: 6496: 6428: 6287: 6082: 6021: 5751: 5259: 5090: 4977: 4658: 4181:

to a group of physically associated stars under study, such as a

3807: 3799: 3791: 3753: 3699: 3593: 3587: 3420: 3242: 3079: 2886: 2764: 2663:

The surface velocity at the equator of a rotating body where the

2275: 1791: 1452: 1413: 1288: 1270: 1182: 1142: 1050:

are often used interchangeably, there are technical distinctions.

1020:

that is a single, tightly bound, contiguous structure, such as a

825: 759: 520: 490: 458: 421: 361: 15858:

Stellar Interiors: Physical Principles, Structure, and Evolution

14171: 13926: 13914: 13572: 13504: 13334: 13184: 13178: 13134: 12898: 12838: 12431: 12409: 12397: 12301:

which, for at least a portion of its life, radiates energy into

12011: 12005: 11877: 11791: 11642: 11332: 11137: 10893: 10538:

A distant, point-like energy source originating from a powerful

10358: 10091: 10016: 9960: 9931: 9877: 9871: 9836: 9578: 9445: 9043:

around an astronomical body, expressed as the angle between the

8899: 8471: 8372: 8251: 8184: 7938: 7891:, though its orbital position with respect to the Earth and the 7746: 7629: 7494: 7456: 7345: 7319: 7196: 7071: 6971: 6965: 6864: 6738: 6726: 6490: 6154: 5933: 5843:

drawn upon the celestial sphere that passes through both of the

5819: 5763: 5509: 5338: 5163: 4889: 4769: 4743: 4693: 4634: 4558: 4488: 4460: 4159: 4070: 4045: 4005: 3861: 3707: 3628: 3523: 3477: 3142: 2944: 2938: 2724: 2497: 2072: 1887: 1547: 1120: 1114: 1028: 730:

or it may be composed of stars from more than one constellation.

686: 353: 300: 254: 203: 201:

the star would show if it were located at a distance of 10

16707: 14311:, and visible planets appear to travel across a band of twelve 14269: 14222: 14199:. They are usually produced when a high-mass object, usually a 13935: 13931: 13566: 12999: 12843: 12755:

that orbits another natural satellite, i.e. "a moon of a moon".

12460:, usually in the context of some region of interest within the 12415: 12316: 12023: 11986: 11901: 11813:

A standard unit of distance equal to the radius of the Earth's

10524: 10415: 10157: 9998: 9794: 9781: 9625: 9454: 9321: 9225: 9175: 9143: 9082: 9039: 8995: 8973: 8947: 8696: 8690: 8499: 8351: 8322: 8292: 8245: 8155: 7752: 7734: 7531: 7512: 7506: 7424: 7391: 7373: 7117: 6959:) and completely darkened by the Moon's own shadow (known as a 6824: 6774: 6576: 6423: 6376: 6163: 6143: 6058:

An archaic term that is sometimes used to refer to the planets

6017: 6007: 5999: 5995: 5991: 5521: 5372: 5366: 5094: 5086: 4887:

A large-scale structure consisting of hundreds or thousands of

4805: 4699: 4426:

that undergoes sudden, dramatic increases in brightness due to

3898: 3457:

defined by the plane of Earth's orbit around the Sun (i.e. the

2616: 2584: 2271: 2243:

around the cometary body. Sometimes a comet can produce a long

2049: 1870: 1645: 1562: 1561:

The process by which the class of subatomic particles known as

1533:

of each body and the distances between them. For example, in a

1515: 1430: 1094:

but is a more complex, less cohesively bound structure than an

770: 601: 567: 508: 437: 282: 225: 15424: 14307: 14253: 14111: 13988: 13920: 13498: 13484: 13340: 13328: 13260: 13150:, a result of the fact that both the body being studied (e.g. 13076: 12926: 12673: 12544: 12519: 12488: 12450: 12379: 11831: 11819:(typically measured from the Sun's center to the layer in the 11795:. Prominences may be hundreds of thousands of kilometers long. 11757: 11636: 11251: 11191: 10992: 10499: 10004: 9763:

are all commonly used as reference planes in various contexts.

9565: 9098:; in some contexts, the two nodes may be distinguished as the 8905: 8826:. It is thought to be divided into two regions: a disc-shaped 8623: 8611:, it is typically used to compare phase differences over time. 8562:

A continuous, gravity-induced change in the orientation of an

8477: 8465: 8058: 7990: 7875: 7647: 7351: 7261:

which a fictitious body would have if it moved in a perfectly

7077: 6933: 6908: 6858: 6816:

The angle between a specified reference direction, called the

6667: 6148: 5652: 4813: 4388: 4173: 4115: 4039: 3920: 3212: 3180: 3148: 2908: 2730: 2718: 1881: 1605: 1541: 1356: 1034: 1022: 985: 714: 692: 445: 270: 231: 191: 14305:

over the course of the year as observed from Earth. The Sun,

14295: 14277: 14230: 14196: 13905: 13680: 13300: 13190: 13156: 13046:

The time it takes for an object to rotate once about its own

12471: 12045: 12039: 11999: 11935: 11929: 11871: 11815: 11779: 11737: 11630: 11569: 11563: 11496: 11460: 11392: 11386: 10571: 10487: 9669: 9595: 9316: 9278: 9269: 8881: 8816: 8449: 8439: 8413: 8308: 8297: 8170: 7893: 7740: 7666: 7317:

and passing through the point directly overhead known as the

7313: 7147: 6945: 6879: 6754: 6531: 6514: 6068: 6063: 5618: 5581: 5555: 5138: 4775: 4435: 4394: 4386:

which do. The fixed stars are typically taken to include all

4333: 4331:, the First Point of Libra represents the point at which the 4278: 4131: 3819: 3747:

defined by an origin at the geometric center of the Earth, a

3695:

interval, with a given epoch as the temporal point of origin.

3656: 3622: 3449: 3344: 3224: 3136: 2712: 2589: 2491: 2455: 2231: 2223: 1973: 1933: 1362: 754: 698: 500: 397: 15973: 15586:, Center for Computational Physics in Hawaii, archived from 11771:

A large, bright, transient feature, often in the shape of a

10473:

A configuration in which two celestial bodies have apparent

7355:

positions which are self-consistent over large areas of sky.

6955:

Earth alternates between completely illuminated (known as a

4430:

on its surface. This change in brightness occurs across the

3580:, which have eccentricity equal to 0), or one with negative 1937:

at which a hypothetical indefinite extension of the Earth's

1134:

Any abstract pictorial symbol used to represent one or more

15091:(Third ed.), Imagine Publishing Limited, p. 151, 14895: 14465: 13909: 13170:

The calculation of the passage of time based on successive

12283: 9679: 9471:

as observed from Earth's orbit. It is equal to 3.2616

9263:

are related by a ratio of small integers. For example, the

9116:, which is coplanar with the reference plane, has no nodes. 7861: 7476:. If it survives to reach the surface, it is then termed a 6883: 6807: 6092: 6016:

with freezing points above 100 K (−173 °C), e.g.

2758:, creating two points at which it crosses the meridian: an 2541: 2154: 1530: 821: 486:. The brighter the object appears, the lower its magnitude. 337: 23:

is a list of definitions of terms and concepts relevant to

12780:

whose mass is smaller than the smallest mass at which the

12555: 12043:

reaches its most northerly or most southerly point in the

11372:

of an object (e.g. the Earth) with respect to the distant

9563:

The point at which a body orbiting the Earth (such as the

8951:. For a binary system, it is typically presented from the 2762:, at which the object reaches its highest point above the 1679:

generated by a rapidly spinning star matches the force of

901:, and how humans might be able to detect extraterrestrial 443:

The point at which a body orbiting the Earth (such as the

16781: 16149: 15891:

A Knowledgebase for Extragalactic Astronomy and Cosmology

12812: 11735:

A standard unit of mass equal to the mass of the Earth's

11489: 11476:, as viewed from a given location on the Earth's surface. 9002: 7069:, interacts with the magnetic field of a body, such as a 7063:

A mostly convex region formed when a plasma, such as the

6123: 5177:

The ratio of the brightness of an astronomical body at a

3936:

that a star will have during part or all of its lifetime.

3930:. This curve predicts the combination of temperature and 1480: 419:

The point at which an orbiting body is furthest from its

14889: 14281:

that extends approximately 8 degrees north or south (in

12842:

that orbit further from the Sun than the Earth, such as

12263:

generated by its rotation. It is by definition equal to

11284:

One half of the longest diameter (the major axis) of an

7867:

The solid, rocky body that orbits the Earth as its only

6363:

A unit of time defined as exactly 365.25 days of 86,400

5370:

which are gravitationally bound to each other and which

4464:

having a size between 1.5 and 2 times that of the Earth.

3829:); or, equivalently, when the Sun's apparent geocentric 3823:(i.e. the two points at which this plane intersects the 2274:

around the Sun is very nearly 5/2 the orbital period of

2070:

Any very large concentration of mass at the center of a

1971:

An imaginary sphere that encompasses the Earth's entire

1749:

A star used for calibration of high-powered teleescopes.

15165:

Publications of the Astronomical Society of the Pacific

12653:

over time based upon its mass and chemical composition.

12128:

of the components change over the course of each orbit.

11689:. The Sun's faculae are most readily observed near the 10683:

A conspicuous trail of enlarged red stars found on the

10578:

and optical spectra are characterized by strong, broad

7273:

as the actual body in its elliptical orbit. Unlike the

6608:. The phenomenon is the basis for the stable orbits of 5364:

A tight, spherical conglomeration of many thousands of

3590:, and are very common in two-body astronomical systems. 3447:, with an origin at the geometric center of either the 2257:

A property of two objects orbiting the same body whose

1140:, events, or theoretical constructs, e.g. those of the 179:, and have surface temperatures of 7,600–10,000 kelvin. 15233:, New York: McGraw-Hill Book Company, pp. 70–124. 14500: 14105:. A white dwarf lacks the mass needed to continue the 12401:

are also star systems. Star systems are distinct from

11515:, the term "sky" is also used as another name for the 10931:

The distance from an astronomical object at which the

9539:

The point at which an orbiting body is closest to its

7897:

causes its visibility to change in a regular cycle of

7000: 6856:

The total amount of energy emitted per unit time by a

5458:

which analyzes minute distortions in the curvature of

4656:, and the brightest such active galaxies are known as 2885:

around it. This type of disk can be found around many

774:; bodies less than one meter in diameter are known as 14650: 14571: 13064:

it is orbiting (rather than to the much more distant

11755:. It is commonly used to express the masses of other 11145:

of a more massive and luminous host galaxy; e.g. the

11125:

was first noted by American astronomer Stephen Saber.

10448:

A method of computing the mean strength of a varying

9405:

expanse that exists beyond the Earth and between all

8670:

The duration of time between the earliest and latest

7470:

A small rock or boulder that has entered a planetary

4709:. Estimates of the duration of one revolution of the 4520:, as viewed from Earth; considered as a point on the 4508:

The direction in space that is directly opposite the

2426: 1545:

is significantly larger than the mass of an orbiting

15748: 15352: 14079:

for a star compared to standard stars with the same

13570:) with respect to a larger, perturbing body (e.g. a 13476:

orbits with the same face always pointed toward its

12600:; or another name for the stellar atmosphere itself. 12474:

could be defined as encompassing some or all of the

11921:

The calculation of the passage of time based on the

11446:

The calculation of the passage of time based on the

10014:. In general, planetary systems include one or more 9740: 9629:

characteristics of the body such that the idealized

6949:

change, the visibility of the side of the Moon that

3011:

at which an orbiting object moves south through the

2552: 657: 644:

at which an orbiting object moves north through the

15664: 15391: 15030:(2nd ed.), New York: Oxford University Press, 13182:(i.e. successive returns of the object to the same 12836:An archaic term that is sometimes used to refer to 12466:. For example, the starfield surrounding the stars 12454:visible in an arbitrarily sized field of view of a 6675:. It can allow normally hidden parts of the Moon's 5585:; centered upon the Sun, e.g. a heliocentric orbit. 5167:

as defined with respect to the center of the Earth.

5141:; centered upon the Earth, e.g. a geocentric orbit. 3742: 3436: 1820:A diagram of the relationships between the Earth's 1269:The branch of astronomy that employs principles of 524:– either the point of minimal distance, called the 14707: 14411:Physics, Formation and Evolution of Rotating Stars 13577: 13229:that is perpendicular to the line of sight of the 11777:, consisting of plasma extending outward from the 10943:. Outside this limit, loose material will tend to 10187:Any slow change in the orientation of an object's 10171:equal or nearly equal to 90 degrees to the body's 9276:, such that Pluto completes two orbits around the 9049:or axis of direction of the orbiting object and a 7526:A measure of the abundance of elements other than 6724:). Though the light-year is often used to measure 6589:of orbital motion, and (in certain scenarios) the 5622:. The heliosphere encompasses the entirety of the 4276:of (0°, 0°) and represents the point at which the 3503:(of a star or planet) The temperature of an ideal 599:An object that has been intentionally placed into 318:and geological or environmental surface features). 15355:Monthly Notices of the Royal Astronomical Society 15292: 14574:Monthly Notices of the Royal Astronomical Society 14442:Astronomical Observations, An Optical Perspective 14257:which have finished contracting and have reached 14251:achieved by newly formed, chemically homogeneous 12869: 12037:Either of the two precise times of year when the 11531: 11064:. It is not necessarily the same as the object's 10848: 9153:, the orbital period is often referred to as the 8025:The horizontal angular distance between the rise 7498:that seemingly radiate from a single area in the 5047:away. The source of most GRBs is theorized to be 5041:radiation which can be detected from billions of 4905:and from smaller aggregates of galaxies known as 3245:. Confusingly, the term has also come to include 3089: 2840: 1956: 1796: 17066: 15559:, Universitätsverlag Göttingen, pp. 54–59, 15057: 14934: 14246: 14236: 14035: 13326:The line that divides the illuminated side of a 11002:. Such objects have often been ejected from the 10803:. The direction of rotation is determined by an 10684: 10278:. The direction of rotation is determined by an 10194: 9366:that an orbiting object would follow around its 7249:that has elapsed since the orbiting body passed 7128: 6312: 6095:, which appear to move independently of the Sun. 5888: 5761:perpendicular to a line from an observer to the 5183:of zero to an idealized flat, fully reflecting, 4936:A gravitationally bound aggregation of up to 50 4721:range from 225 to 250 million terrestrial years. 4317: 4256: 3913: 3671: 3367: 1381: 828:that is occupied by numerous irregularly shaped 243: 13641: 12050: 11464:. The fundamental unit of sidereal time is the 11336:passage. It represents the moment at which the 10474: 9811: 9593:The point at which a body orbiting the Earth's 7200:passage. It represents the moment at which the 6752:An optical effect seen in stars (including the 5444: 5413:Any very large distribution of mass, such as a 4644:which, when active, can generate a much higher 4271: 3830: 3733: 3286:A hotter and more massive star, in contrast to 2918:. The classification is used mostly in amateur 2400: 2099: 2061: 2041:that typically exhibit characteristics of both 1714: 530:, or the point of maximal distance, called the 395:The point at which a body orbiting the Earth's 223:A roughly circular mass of diffuse material in 43: 15717: 15482:HubbleSOURCE: Constellation Mythological Forms 15397: 14862: 14713: 14459: 12729:detectable at submillimetre wavelengths (i.e. 11495:Everything that lies above the surface of the 10393: 10213: 10058: 8993:The set of parameters that uniquely define an 8808:A vast theoretical cloud of predominantly icy 8419: 8090:based on the acquisition of information about 7287: 5630: 3751:created by projecting the Earth's terrestrial 2986:, such that normal atoms cannot exist in them. 2609:Any model concerning the origin of either the 2476: 1713:. Brown dwarfs can still generate energy from 1615:. The term is often used interchangeably with 1326:A slow, continuous, gravity-induced change (a 16767: 15989: 15854: 15298: 14626: 14388:, Cambridge, UK: Cambridge University Press, 14385:Cambridge Illustrated Dictionary of Astronomy 14315:within this belt as the Earth orbits the Sun. 12924:stellar explosion occurring during a massive 11835:and astronomical objects relative to the Sun. 11761:and astronomical objects relative to the Sun. 11330:, while generally trending southward at each 9777:of an orbital plane of a distant star system. 8765:A celestial event that occurs when a distant 8731:The practice and study of directly observing 8533: 8162:that are radio sources and display prominent 7255:, expressed as the angular distance from the 7194:, while generally trending northward at each 6892:. Luminosity is related to but distinct from 6395: 5767:that passes through the point of observation. 5320:equal to 35,786 kilometres (22,236 mi); 5281: 4593: 3974:by matter (dust and gas) between an emitting 3642:A list or table of the expected positions of 3427: 2489:and the accompanying magnetic field from the 2194: 2187: 1789:that is coplanar with the body's terrestrial 195:'s absolute brightness. It is defined as the 15957:"Glossary of (comet and) astronomical terms" 15855:Hansen, Carl J.; Kawaler, Steven D. (1999), 15556:3D-Spectroscopy of Dense Stellar Populations 15519: 15346: 15199: 15060:Astronomy and Astrophysics Supplement Series 14644: 14181:, yet displays an anomalous level of excess 14176: 13536: 13241:and its measured distance from the observer. 13080:), which is not necessarily the same as the 12957:experienced at the equatorial surface of an 12183: 11939:. The fundamental unit of solar time is the 11888: 11681:of the Sun that form in the canyons between 10667:into space. These objects are the basis for 10557: 10539: 10112: 9901: 9006:A diagram showing four of the six canonical 8789:eclipses are specific types of occultations. 8706:), and therefore result in a high degree of 8676:made by astronomers of an object within the 8671: 8482: 8296:, whose orbit brings it into proximity with 8279: 8262: 8076: 7387:easily visible from the Northern Hemisphere. 7133:. These stars are characterized by being in 7015:that might explain the apparent presence of 6477: 6233:and rotational planes comprising the system. 6133: 5453: 5326:are a special case of geosynchronous orbits. 4651: 4639: 4563: 4493: 4225: 3581: 3482: 2919: 2564:cosmic microwave background radiation (CMBR) 2302:parameters, which may suggest that they are 2290:. That is, either they have nearly the same 2077: 2000: 1283:and phenomena, examining properties such as 829: 780:; very large asteroids are sometimes called 763: 15945:, Space Telescope Science Institute (STScI) 15801: 15718:Jaschek, Carlos; Jaschek, Mercedes (1990), 15711: 15658: 15631: 15600: 15446: 15265: 15051: 14989: 14744: 14565: 14538: 14494: 14445:, Cambridge University Press, p. 109, 14080: 13963:disconnected constituent parts of a larger 13822: 12086: 11384:(rather than to its primary star, e.g. the 10442: 9223:The situation that occurs when two or more 8820:at distances ranging from 2,000 to 200,000 8628: 7993:Morgan–Keenan stellar classification system 7903:when viewed from the Earth. The adjectival 7822: 7558:. Micrometeorites are a major component of 5680:across this chart over the course of their 5662:may be substituted for luminosity, and its 5155:by a straight line that passes through the 4762: 4546: 3083: 2981: 1190: 1044:. Though the terms astronomical "body" and 758:at a distance no greater than the orbit of 724:. An asterism may form part of an official 16774: 16760: 15996: 15982: 15848: 15546: 15418: 15278:, Cambridge University Press, p. 87, 15222: 15156: 15019: 15017: 15015: 14940: 14868: 14717:Evolution of stars and stellar populations 14714:Salaris, Maurizio; Cassisi, Santi (2005), 14551:, Cambridge University Press, p. 80, 13839: 13659:1. The passage of a particular 13387: 12803: 12709: 12626: 12076: 11654: 11010: 10979: 10853:, the celestial equivalent of terrestrial 10362:; they are thought to form out of smaller 10020:, though such systems may also consist of 9888: 9865:that is geologically differentiated or in 9623:alone, or any force which complicates the 9147:around another object. For objects in the 8750: 8723: 8707: 8269: 7670:orbits with a period of 240 million years. 6708:: approximately 9.46 trillion kilometres ( 5645: 4755: 3990: 3988:being greater for blue light than for red. 3824: 3393: 3185:which they may form a co-moving pair or a 2974:. These stars are in an advanced state of 2845:, the celestial equivalent of terrestrial 2357: 2239:on a comet's surface, producing a visible 1484:Two bodies of similar mass orbit a common 15815: 15762: 15678: 15526:Andersen, J. (2000), Livio, Mario (ed.), 15374: 15305:, Cambridge University Press, p. 4, 15104: 14972: 14954: 14909: 14672: 14629:The Facts on File Dictionary of Astronomy 14603: 14585: 14529: 14432: 13874: 13588:of each body, including the small body's 13488:, which is tidally locked with the Earth. 13093: 12942:is triggered into runaway nuclear fusion. 12750: 12655: 12525: 11985:A stream of charged particles, primarily 11685:. They are produced by concentrations of 10915: 10746: 10485:is perpendicular to the direction of the 9570: 9236: 7510:, and hence they follow roughly the same 6615: 6274: 6168: 5986:composed mainly of elements heavier than 5899: 5573:With reference to, or pertaining to, the 5396: 5274: 5252: 5131:With reference to, or pertaining to, the 5089:gases rather than heavier elements, e.g. 5017: 4811:A large, gravitationally bound system of 4344: 4289: 3688:, because such quantities are subject to 3649: 3586:. Elliptical orbits take the shape of an 3569: 3507:that would emit the same total amount of 3305: 2805:. A debris disk can be discerned from an 2515: 2367: 2083: 2036: 1898: 1621:, though the latter can also refer to an 1429:; Earth's axial tilt is the cause of the 1197: 1135: 1052: 967: 793: 450: 288:A measure of the proportion of the total 35:and phenomena that originate outside the 15795: 15742: 15644:, Springer Theses, Springer, p. 9, 15525: 15130: 15084: 14836: 14834: 14832: 14830: 14828: 14544: 14401: 14377: 14375: 14373: 14371: 14261:, with energy being derived solely from 13951: 13789: 13632: 13625: 13601: 13357: 13346: 13311: 13104:; Earth's synodic day is often called a 12964: 12775: 12724: 12139: 11952: 11648: 11120: 11078: 10897:. Ring systems are common components of 10823: 10740: 10658: 10630: 10505: 10351: 10308:and estimated distance. For planets and 10166: 10100: 9893:, but excluding smaller objects such as 9497: 9430: 9406: 9319:at which an astronomical body or object 9290: 9136: 9093: 9001: 8971:A parameter that determines how much an 8892: 8772: 8744: 8732: 8514: 8458: 8329: 8091: 7675: 7600:that undergoes very small variations in 7366: 7096: 6977: 6869: 6817: 6671:as seen from the Earth, a result of the 6622: 6268: 6211:The imaginary plane passing through the 6112: 6042: 5730: 5605: 5430:A luminous red galaxy (LRG) acting as a 5425: 5321: 5028: 4866: 4824: 4686: 4591:, where the Milky Way appears brightest. 4369: 4026: 3975: 3938: 3683: 3643: 3592: 3495: 3488: 3386: 3129: 2901: 2891: 2811: 2705: 2453:that surrounds cooler stars such as the 2384: 1984: 1874: 1815: 1582: 1479: 1434: 1300: 1278: 1239: 1089: 1045: 1015: 846:. The asteroid belt is often called the 544: 320: 15637: 15452: 15243: 15205: 15078: 15023: 15012: 14995: 14826: 14824: 14822: 14820: 14818: 14816: 14814: 14812: 14810: 14808: 14750: 14627:Daintith, John; Gould, William (2009), 14134: 13956:, whose size it is possible to measure. 13366: 12595: 12094: 11184: 10298: 10051: 9798:the Sun, which is massive enough to be 9207:for the orbits of other objects in the 9202: 9111: 9087: 9050: 9021: 8977:deviates from a perfect circle. For an 8963: 8508: 8335: 7811: 6893: 6835: 6524:but far larger, and is home to several 6471: 6347: 6324: 5893:, these stars are positioned where the 5675: 5657: 5432: 5121:that is the precise shape of the Earth. 4526:, the Milky Way's anticenter is in the 4296: 4270:, the First Point of Aries defines the 4211: 4037:. The term is generally not applied to 4010: 3945: 3814:extended indefinitely in all directions 3355: 3012: 2874: 2794: 2672: 2280: 1699:that is too low in mass to sustain the 1153: 834:ranging in size from dust particles to 809: 645: 591: 455:) is furthest from the Earth. Contrast 371:belonging to the more general class of 274:. A galaxy hosting an AGN is called an 196: 17067: 16889:Electrical and electronics engineering 16874:Developmental and reproductive biology 15606: 15552: 15529:Unsolved Problems in Stellar Evolution 15271: 15228: 15162: 14438: 14414:, Astronomy and Astrophysics Library, 14407: 14381: 14121: 14005: 13851: 13770: 13695: 13616: 13529: 13471: 13293: 13224: 13213: 12973:(m/s) or as a multiple of the Earth's 12958: 12944: 12931: 12744: 12667:generated by the convective motion of 12648: 12568: 12165: 12016: 11906: 11847: 11675:Solar faculae are bright spots in the 11325: 11090:of a star to vary as rotation carries 10997: 10886: 10858: 10830: 10728: 10463:measurements taken at different times. 10452:. It is determined by calculating the 10370: 10315: 10290: 10027: 9965: 9788: 9478: 9345: 9298: 9272:exists in a stable 2:3 resonance with 9180: 9029: 8910: 8821: 8766: 8714: 8563: 8526: 8301: 8238: 7956: 7931: 7868: 7851: 7773: 7757: 7371:, 103 of which were catalogued as non- 7311:A line running north–south across the 7295: 7214: 7189: 7095:scale indicating the brightness of an 7010: 6772:The imaginary line connecting the two 6569: 6568:Any of a set of points near two large 6507: 6318: 6280: 6262: 5963:systems are examples of hypergalaxies. 5850: 5849:and is therefore perpendicular to the 5790: 5681: 5610:which surrounds and is created by the 5291: 5225: 5002: 4971: 4848: 4761:A star or cluster's distance from the 4737:experienced by objects subject to the 4500: 4399: 4338: 4305: 4283: 3925: 3854: 3812: 3770: 3764: 3726: 3538: 3464: 3406: 3373: 3258: 3229: 2975: 2850: 2679: 2326: 1977:and is stationary with respect to the 1931:One of two coordinates in the Earth's 1892: 1855: 1828: 1694: 1661: 1333: 1126: 1095: 1071: 990: 917: 892: 820:located roughly between the orbits of 613: 293: 16755: 15977: 15610:Formation and Evolution of Exoplanets 14996:Einasto, J. (1978), "Hypergalaxies", 14416:Springer Science & Business Media 14368: 14300: 14282: 14018: 13782: 13760: 13660: 13583: 13176:of an astronomical object, such as a 13127: 13047: 12974: 12891: 12557:Morgan–Keenan spectral classification 12500: 12461: 12402: 12189: 11864: 11516: 11431: 11379: 11348:in the Southern Hemisphere. Contrast 11289: 11236: 11059: 11053: 11003: 10985: 10898: 10690: 10503:at its first and last quarter phases. 10188: 9971: 9758: 9752: 9728: 9706: 9688: 9636: 9462: 9449:as seen from the Earth (not to scale) 9443:shift of a star at a distance of one 9437: 9230: 9008: 8978: 8916: 8569: 8489: 8177: 7325: 7280: 7238: 7212:in the Southern Hemisphere. Contrast 7024: 6841: 6791: 6609: 6218: 6146:that exists in the space between the 6097: 5938: 5812: 5784: 5778: 5742: 5656:; depending on the usage, the star's 5536: 5414: 5405: 5377: 5200: 5193: 5161:and an observer; i.e. the observer's 5150: 4943: 4860: 4842: 4521: 4473: 4311: 4250: 4204: 4197:The first use of a newly constructed 4141:) are most readily observed near the 3904: 3842: 3758: 3716: 3677: 3599: 3400: 3360:for describing the position of other 3349: 2753: 2508: 2416: 2270:. For example, the orbital period of 2169: 1944: 1938: 1905: 1821: 1784: 1751: 1534: 1524: 1339: 1101: 945: 663: 584: 537: 465: 258:displaying a much higher than normal 181: 16735: 15572: 15496: 15398:Schrijver, C. J.; Zwaan, C. (2008), 15299:MacEvoy, Bruce; Tirion, Wil (2015), 15136: 14805: 14781: 14653:The Astrophysical Journal Supplement 14245:The sequence of positions along the 14163:X-ray bright optically normal galaxy 14096: 14075:A reference to the faintness of the 13994: 13430: 13424: 13278: 13074:(in the case where the primary is a 13053: 13022: 13016: 12989: 12861: 12797: 12757: 12677:, responsible for phenomena such as 12617: 12604: 12245:standard acceleration due to gravity 12123: 12069: 12062: 11958: 11784: 11695:. Faculae occur on other stars (see 11660: 11604: 11556: 11367: 11307: 11113: 10815: 10789: 10751:. Regular moons are thought to form 10734: 10668: 10562:. Quasars emit radiation across the 10492: 10314:, this distance is usually given in 10207:that was explained by the theory of 9941: 9673: 9663: 9575:) is closest to the Earth. Contrast 9242: 9215: 9154: 9105: 9057: 8861: 8520: 8403:that is composed almost entirely of 8220: 8063: 7764: 7716: 7681: 7659: 7382: 7163: 6338: 6086: 5948: 5824: 5604:The vast, bubble-like cavity in the 5315: 5303: 5264: 5143: 4949: 4948:. Larger aggregations may be called 4818: 4790: 4704: 4509: 4405: 4051: 4017: 3789:Of, relating to, or occurring at an 3513: 3293:rather than of all stars in general. 3246: 3216:belonging to a category of ordinary 3112: 3075:point of closest approach to the Sun 2924:to distinguish faint objects in the 2857: 2740:, etc.) across the observer's local 2648: 2641: 2631:origin, evolution, and eventual fate 2394: 2350: 2297: 2235:. The energy from the Sun vaporizes 2012: 1771: 1652: 1245: 997: 670: 252:A compact region in the center of a 15473: 15401:Solar and Stellar Magnetic Activity 15325: 15246:Introduction to Celestial Mechanics 15139:"Al Khwarizmi: A Medieval Polymath" 15137:Umar, Khalid Bin (18 August 2019), 14288: 14140: 13858: 13845: 13753:The angle between the direction of 13589: 13381: 13145: 13087: 13010: 12691: 12586: 12577: 12421: 12215: 11970: 11922: 11763: 11690: 11597:and because its rotational axis is 11447: 11413: 11344:in the Northern Hemisphere and the 11127: 11034:to radiation at a given depth. See 10769: 10767:, which are thought to be captured. 10762: 10675: 10551: 9978: 9911: 9860: 9806:(but not massive enough to achieve 9765: 9746: 9352: 9332: 9258: 9099: 8985: 8300:, generally by being less than 1.3 8032: 7581: 7417: 7268: 7262: 7244: 7208:in the Northern Hemisphere and the 6829: 6697: 6665:A slight oscillating motion of the 6543: 6244: 6190: 5844: 5686:. Hence, knowing a star's mass and 5356: 5314:. All geosynchronous orbits have a 5297: 5247: 5169: 4942:, each at least as luminous as the 4611: 4142: 3836: 3817:, passes through the center of the 3776: 3575: 3574:of less than 1 (often inclusive of 3545: 3470: 3354:. The ecliptic is widely used as a 3287: 3153: 3095: 3025: 2747: 2258: 2249: 2030: 1963: 1441: 1424: 1380:, and is the cause of the apparent 1318: 1252: 1164: 965:of the visible component. See also 572: 513: 401:is furthest from the Sun. Contrast 330: 229:around a central object, such as a 140: 13: 14620: 13808: 13455: 13236: 12828: 12700: 12056: 11964: 11404: 11350: 11267: 11044: 11036: 10863:into 24 hours, each of 60 minutes. 10839: 10615: 10591: 10510:A moon or planet is said to be in 10255: 9075: 9044: 9015: 8945:A schematic diagram of a complete 8784: 8778: 8653: 7880: 7833:normalized polar moment of inertia 7802: 7695: 7623: 7595: 6950: 6766: 6687: 6519: 6440: 6369: 6354: 6228: 6050: 5917:, forms the dividing line between 5869: 5693: 5669: 5530: 5467: 5389: 5205:or otherwise) with respect to the 5060: 4955: 4912: 4906: 4900: 4854: 4664: 4602: 4575: 4537: 4527: 4421: 4323: 4262: 4244: 4009:, i.e. all objects not covered by 3875: 3848: 3532: 3278: 3217: 3055: 3033: 2988: 2950: 2735: 2460: 2291: 2115:. One measure of this activity is 2018: 1835: 1741: 1708: 1675:The surface velocity at which the 1636: 1418: 954: 725: 168: 162: 14: 17096: 16919:Genetics and evolutionary biology 15879: 15275:Astronomy: A Physical Perspective 15110: 14317: 14069: 14024: 13776: 13595: 13465: 13112: 13081: 12890:. These are typically found at a 12684: 12642: 12390: 12333: 12326: 12156: 12147: 11882: 11772: 11592: 11586: 11561:of the Earth with respect to the 11465: 11419: 11294: 11219: 11183:Rapid variations in the apparent 11157: 11071: 10904: 10733:following a relatively close and 10604: 10422: 10363: 10140: 10134: 10045: 10021: 9894: 9882: 9842: 9817: 9727:from which to measure and define 9723:An arbitrarily chosen, imaginary 9630: 9506: 9373: 9361: 9264: 9208: 9148: 9118: 8831: 8809: 8677: 8613: 8544: 8398: 8365: 8256: 8069: 7982: 7964: 7949: 7943: 7898: 7794: 7779: 7634: 7566: 7536: 7410:The visible passage of a glowing 7357: 7274: 7048: 7036: 6938: 6886:, and is often given in terms of 6878:units, luminosity is measured in 6744: 6648: 6525: 6501: 6446: 6292: 6253: 6158:. This medium mainly consists of 6072:than the Earth and hence, in the 6025: 5981: 5897:of both variable classes overlap. 5729:The approximate region around an 5623: 5309: 5098: 5076: 4962: 4894: 4879: 4710: 4381: 4182: 4136: 4090: 4075: 4032: 3689: 3563: 3442: 3361: 3120: 3067: 3061: 3018: 3006: 2969: 2931: 2913: 2880: 2865: 2800: 2594: 2338: 2110: 2054: 1923: 1207: 1147: 1107: 960: 841: 815: 787: 747: 741: 651: 639: 621: 606: 343: 215: 16734: 16723: 16722: 16493:Southern African Large Telescope 15376:10.1111/j.1365-2966.2008.14227.x 14605:10.1111/j.1365-2966.2004.07627.x 14351:List of common astronomy symbols 14175:that does not appear to have an 13978: 13781:, and also one of six canonical 13723: 13701: 13446: 13423:. This can cause changes in the 13418: 13400: 13287: 13252: 13171: 13121: 13065: 12937: 12791: 12610: 12493: 12384: 12302: 12206: 12103: 11940: 11820: 11710: 11676: 11623: 11614: 11580: 11550: 11504: 11478: 11453: 11438: 11425: 11373: 11300: 11257: 11243: 11229:perihelion precession of Mercury 11166: 11065: 10938: 10932: 10874: 10808: 10428: 10350:embryo that originated within a 10326: 10309: 10283: 10118: 10106: 10009: 9772: 9734: 9599:is closest to the Sun. Contrast 9307: 9295:A planetary system showing a 1:2 9248: 9161: 8341: 8008: 7588: 7559: 7484: 7171: 7107: 7055: 7042: 6984: 6931:The shape of the portion of the 6703: 6439:, which forms a two-dimensional 6427:body relative to another, as an 6126:International Astronomical Union 5937:accompanied by multiple smaller 5918: 5802: 5705: 5687: 5663: 5574: 5473: 5178: 5042: 4836: 4830: 4780: 4732: 4723: 4120: 3626:and an orbiting body, such as a 3264: 3252: 3186: 3102: 2963: 2912:or an object within the Earth's 2818: 2545: 2502: 2428:International Astronomical Union 2407: 2332: 2024: 1978: 1950: 1616: 1598: 1493: 1195:and in other forms of shorthand. 907: 874: 800: 379: 372: 16923:Cellular and molecular biology 15927:, European Southern Observatory 15319: 15302:The Cambridge Double Star Atlas 15237: 15113:"Gcal 4.1: Appendix N Glossary" 14846:The Astronomical Almanac Online 14701:United States Naval Observatory 14689: 14341:List of astronomical catalogues 14187: 13964: 13802: 13765:, as measured from the nearest 13732: 13685: 13523: 13516: 13490: 13470:is low, the result is that the 13305: 13162: 13099: 12913: 12885: 12879: 12846:. The name originated from the 12819: 12785: 12735: 12561: 12351: 12320: 12199: 12130: 11855: 11797: 11667: 11598: 11358: 11085: 11023: 10949: 10719: 10649: 10545: 10512: 10480: 10248: 10081: 9813:cleared its neighbouring region 9742:longitude of the ascending node 9657: 9609: 9472: 9326: 9074:One of two points at which the 9066: 8922: 8852: 8645: 8575: 8389: 8359: 8313: 8117: 8097: 8039: 7750:nor originally classified as a 7724: 7652: 7601: 7471: 7454:A solid piece of debris from a 7435: 7365:One of a set of 110 "nebulous" 7256: 7222: 7122: 7064: 7030: 6810:longitude of the ascending node 6731: 6404: 6381: 6212: 6177: 5931:A system consisting of a large 5912: 5906: 5736: 5639: 5611: 5565: 5479: 5349: 5343: 5328: 5236:geosynchronous equatorial orbit 5218: 5212: 4970:A collective name for the four 4919: 4645: 4569: 4316:, used as a reference point in 4255:, used as a reference point in 4203:or other instrument to take an 4149: 3931: 3487:orbit the Sun with only slight 3412: 3379: 3295: 3193: 3073: 2467: 2344: 2308: 2090: 2023:, i.e. generally inward of the 2006: 1847: 1802: 1610: 1553: 1519:. The barycenter is one of the 1486: 1327: 1261: 925: 856: 668:to describe an orbit. Contrast 659:longitude of the ascending node 403: 309: 259: 236: 208: 174: 164:Harvard spectral classification 135: 15027:Oxford Dictionary of Astronomy 14207:and a companion star are in a 14087: 13912:and their contents, including 13904:1. The entirety of 13801:between the mass or intrinsic 13787:used to characterize an orbit. 13754: 13608: 13579:restricted three-body problems 13509: 13437: 13393: 13375: 13139: 13105: 13029: 13003:in which an object orbits its 12919: 12850: 12718: 12455: 12360: 12109: 11837: 11701: 11523: 11510: 11397: 11238:precession of the Earth's axis 11235:of the Earth–Moon system, and 11150: 11091: 11084:A phenomenon which causes the 10923: 10865: 10624: 10407:of revolution and rotation at 10345: 10336: 10147: 10039: 9924: 9697: 9648: 9516:. It can be determined from a 9452: 9384: 9338: 8897:, such as the trajectory of a 8757: 8738: 8589: 8437:The appearance of the Earth's 8085: 7886: 7688: 7640: 7607: 7575: 7545: 7518: 7499: 7477: 7411: 7250: 6914: 6906:Of or relating to the Earth's 6887: 6846:used to characterize an orbit. 6798: 6779: 6702:in vacuum would travel in one 6506:, extending between 30 and 50 6453: 6106: 6076: 6032: 5954: 5925: 5862: 5831: 5783:, the angular distance on the 5712: 5699: 5596: 5543: 5499: 5383: 5296:about the Earth, i.e. with an 5206: 5156: 5132: 5054: 5048: 5011: 4872: 4865:. Most of the galaxies in the 4796: 4748: 4716: 4632:The region at the center of a 4552: 4515: 4482: 4443: 4375: 4351: 4198: 4189: 3999: 3890:gravitational potential energy 3783: 3744:astronomical coordinate system 3438:astronomical coordinate system 3411:(green), which is permanently 3170: 3159: 3048:extended scattered disc object 2925: 2831: 2785: 2687: 2524: 2459:. It can be observed during a 2383:A phenomenon during which two 2375: 2203: 1864: 1685: 1589: 1576: 1539:where the mass of the central 1492:external to both, as usual in 1433:. Axial tilt is distinct from 1387: 1176: 1170: 885:extreme-environment adaptation 781: 775: 719: 589:used to characterize an orbit. 578: 525: 427: 153: 1: 16003: 15961:International Comet Quarterly 15893:, NASA/IPAC, January 10, 2006 15580:"Components of the Milky Way" 14468:Astrophysical Journal, Part 1 14361: 13666: 13559: 13522:The gradual reduction of the 13318: 13230: 13126:visible in the second body's 12878:One of a class of very large 12678: 12549: 11977: 11946: 11913: 11894: 11719: 11574: 11471: 11149:is a satellite galaxy of the 10465: 10421:A highly magnetized rotating 10179: 10033: 9601: 9585: 9547: 9416: 9255:mean-motion orbital resonance 9196: 8930: 8868: 8814:hypothesized to surround the 8791: 8683: 8285: 8124: 8111: 7706: 7429: 7338: 7153: 7029:. Examples of MACHOs include 6848: 6834:, as measured on a specified 6785: 6614:and is commonly exploited by 6483: 6346:A physical state in which an 6235: 6183: 6011: 5856: 5796: 5769: 5587: 5563:that is the shape of the Sun. 5485: 5149:The point projected upon the 5123: 4937: 4458:The apparent uncommonness of 4450: 4442:. Most flare stars are faint 4412: 4165: 4082: 3954: 3867: 3608: 3458: 3202: 2752:along a circular path on the 2741: 2634: 2610: 2571: 2433: 2288:margin of observational error 2042: 1915: 1841: 1840:around the Sun, known as the 1808: 1627: 1609:orbiting around their common 1501: 1394: 1371: 1349: 1307: 1159: 1039: 975: 835: 531: 357:) compared to adjacent areas. 328:(center) is a prominent dark 130: 15667:Astronomy & Astrophysics 15272:Kutner, Marc Leslie (2003), 15244:Moulton, Forest R. (1970) , 14898:Astronomy & Astrophysics 13707: 13477: 13454:The net result of continued 13243: 13059: 13004: 12904: 12442: 11541: 11204: 11029: 10880: 10850:equatorial coordinate system 10798: 10756: 10379: 10273: 10172: 10125: 9991: 9828: 9618: 9540: 9522: 9415:. Most of the volume of the 9367: 9360:The hypothetical, idealized 9283: 9186: 8952: 8701: 8635: 8429: 8196: 8189: 8146:An early classification for 8026: 7786: 7614: 7462: 7446: 7332: 7083: 6657: 6495: 6303: 6297:, which are thought to form 6286: 5972: 5789:measured westward along the 5447:gravitational-wave astronomy 5258: 5105: 5067: 4657: 4319:celestial coordinate systems 4258:celestial coordinate systems 4135:in particular, faculae (see 4125:formed by concentrations of 3806: 3790: 3752: 3736:equatorial coordinate system 3634: 3419: 3369:celestial coordinate systems 3066:in the outer reaches of the 2842:equatorial coordinate system 2763: 2704:The apparent movement of an 2629:The scientific study of the 2621: 2601: 2247:radiating away from the Sun. 2101:chromospheric activity index 1958:equatorial coordinate system 1798:equatorial coordinate system 1790: 1412: 1230: 1141: 897:, the possible existence of 519: 457: 420: 7: 15943:HubbleSite – Reference Desk 15921:"ESO Astronomical Glossary" 15909:, Sky & Telescope Media 15721:The Classification of Stars 15697:10.1051/0004-6361/201015809 15553:Husser, Tim-Oliver (2012), 14928:10.1051/0004-6361/201629126 14674:10.1088/0067-0049/187/1/228 14531:10.1051/0004-6361:200810377 14382:Mitton, Jacqueline (2007), 14329: 14293:, the apparent path of the 14248:Hertzsprung–Russell diagram 14170: 14160: 14044: 13925: 13913: 13896: 13882: 13829: 13571: 13549: 13503: 13408: 13333: 13183: 13177: 13133: 13037: 12897: 12837: 12765: 12632: 12533: 12508: 12430: 12408: 12396: 12368: 12341: 12259:and, less importantly, the 12242: 12173: 12029: 12010: 12004: 11876: 11790: 11696: 11641: 11436:as observed from the Earth. 11331: 11315: 11275: 11174: 11136: 10957: 10892: 10805:inertial frame of reference 10710: 10686:Hertzsprung–Russell diagram 10530: 10395:pseudo-synchronous rotation 10357: 10280:inertial frame of reference 10263: 10230: 10216:precession of the equinoxes 10196:precession of the equinoxes 10090: 10067: 10015: 9959: 9949: 9930: 9876: 9870: 9850: 9835: 9714: 9577: 9530: 9520:of the stellar variability. 9444: 9392: 9126: 8936: 8898: 8799: 8661: 8554: 8525:orbits and 180 degrees for 8470: 8378: 8371: 8250: 8228: 8204: 8183: 8140: 8047: 8016: 7998: 7972: 7937: 7917: 7830: 7745: 7744:that is neither a dominant 7628: 7594:A stellar object such as a 7493: 7455: 7397: 7344: 7318: 7303: 7289:mean-motion resonance (MMR) 7195: 7179: 7130:Hertzsprung–Russell diagram 7070: 7003:Massive compact halo object 6970: 6964: 6922: 6863: 6737: 6725: 6630: 6551: 6489: 6461: 6412: 6314:Hertzsprung–Russell diagram 6198: 6153: 5932: 5890:Hertzsprung–Russell diagram 5818: 5762: 5720: 5633:Hertzsprung–Russell diagram 5616:emanating from the Earth's 5508: 5337: 5233: 5199:The position of an object ( 5162: 4927: 4888: 4768: 4742: 4692: 4672: 4633: 4619: 4557: 4487: 4459: 4359: 4234: 4158: 4069: 4059: 4044: 4004: 3951:for stars of different mass 3915:Hertzsprung–Russell diagram 3860: 3706: 3632:, as it appears from Earth. 3627: 3553: 3522: 3476: 3321: 3313: 3141: 3041: 2996: 2943: 2937: 2849:. Coordinates north of the 2723: 2695: 2654: 2561: 2555:cosmic microwave background 2532: 2496: 2316: 2177: 2105:A parameter indicating the 2071: 1886: 1658: 1567: 1546: 1468:spherical coordinate system 1402: 1383:precession of the equinoxes 1332:) in the orientation of an 1277:to determine the nature of 1119: 1113: 1079: 1060: 1027: 1005: 933: 864: 752:, i.e. one that orbits the 732: 704: 685: 662:, is used along with other 629: 552: 473: 411: 387: 352: 299: 253: 202: 10: 17101: 17024:Probability and statistics 15781:10.1051/0004-6361:20030163 15751:Astronomy and Astrophysics 15726:Cambridge University Press 15607:Barnes, Rory, ed. (2010), 15453:Ridpath, Ian, ed. (2018), 15428:Astronomy and Astrophysics 15328:Astronomy and Astrophysics 15252:: Dover, pp. 322–23, 15229:Aitken, Robert G. (1935), 14545:Perryman, Michael (2009), 14510:Astronomy and Astrophysics 14346:List of astronomy acronyms 14103:electron-degenerate matter 13690:from the two objects, the 13651: 13565: 13534:due to tidal interactions. 13027:as the primary's rotation. 13021:of the primary and in the 12998: 12955:gravitational acceleration 12517:The outermost region of a 12480: 12414: 12253:gravitational acceleration 12022: 12021:, and the plasma tails of 11900: 11863:The gravitationally bound 11603:to its orbital plane. One 11211: 11189:, color, or position of a 11028:, which describes the net 10606:gravitational perturbation 10533:quasi-stellar radio source 10222: 10156: 9997: 9793: 9624: 9555: 9382:at a given moment in time. 9320: 9224: 9174: 9142: 9081: 9038: 8994: 8972: 8946: 8838: 8695: 8689: 8498: 8291: 8244: 8182:exactly opposite from the 7909: 7751: 7733: 7645:, formed from billions of 7633:that includes the Earth's 7511: 7505: 7423: 7372: 7285:mathematically convenient. 7145:in their core region. The 7116: 6823: 6822:, and the direction of an 6773: 6716:) or 5.88 trillion miles ( 6575: 6451:that may exist in reality. 6422: 6398:Kelvin–Helmholtz mechanism 6375: 6201:Laplace's invariable plane 5923:and hydrogen-fusing stars. 5795:from the observer's local 5749: 5526:spectral lines of hydrogen 5513:powered by young, massive 5371: 5365: 5336:Any very large or massive 4698: 4596:galactic coordinate system 3897: 3797: 3697: 3430:ecliptic coordinate system 3128:The apparent motion of an 2980:and have suffered extreme 2906:that is not an individual 2583:consisting of high-energy 2197:clearing the neighbourhood 2189:cis-Neptunian object (CNO) 2048: 1991: 1603:consisting of exactly two 1514: 1450: 962:gravitational perturbation 769: 600: 566: 507: 488: 359: 224: 16794: 16717: 16509: 16486:Large Binocular Telescope 16451:Extremely Large Telescope 16444:Extremely large telescope 16417: 16300: 16240: 16161: 16123: 16084: 16077: 16011: 15804:The Astrophysical Journal 15505:Kepler Mission Star Field 15456:A Dictionary of Astronomy 15085:Westlake, Hannah (2015), 14943:The Astrophysical Journal 14754:A Dictionary of Astronomy 14306: 14267: 14252: 14220: 14136:absolute visual magnitude 14110: 13987: 13919: 13714: 13497: 13483: 13339: 13327: 13292:, approximately 75 to 90 13259: 13196: 13075: 12971:meters per second squared 12925: 12672: 12543: 12518: 12487: 12449: 12413:and other bodies such as 12378: 12297:held together by its own 11890:small Solar System bodies 11830: 11756: 11635: 11250: 11190: 10991: 10778: 10522: 10498: 10413: 10114:small Solar System bodies 10003: 9904:planetary differentiation 9875:-like geology, such as a 9779: 9564: 9483:. The word "parsec" is a 8904: 8700:around the Sun (or other 8622: 8476: 8464: 8320: 8104:electromagnetic radiation 8079:multi-messenger astronomy 8057: 7874: 7646: 7389: 7350: 7076: 6932: 6907: 6857: 6666: 6585:of the large bodies, the 6479:small Solar System bodies 6223:and perpendicular to its 6147: 5651: 4841:, each of which orbits a 4812: 4803: 4568:of 4.100 ± 0.034 million 4387: 4172: 4114: 4105: 4038: 3972:electromagnetic radiation 3919: 3721:and equidistant from its 3509:electromagnetic radiation 3484:small Solar System bodies 3211: 3179: 3147: 2907: 2729: 2717: 2485:A significant release of 2441: 1880: 1716:gravitational contraction 1643: 1604: 1540: 1462:. When combined with the 1355: 1033: 1021: 984: 831:small Solar System bodies 765:small Solar System bodies 713: 691: 678: 542:have exactly two apsides. 444: 435: 280: 269: 230: 190: 16458:Gran Telescopio Canarias 15248:(2nd revised ed.), 15145:, www.tawarikhkhwani.com 14974:10.3847/1538-4357/aafac8 14294: 14276: 14229: 14154: 13679: 13299: 13286:The boundary within the 13189: 13155: 12609:of gases encompassing a 12198:and the measurements of 12118:. This is caused by the 12044: 12038: 11998: 11934: 11928: 11870: 11814: 11778: 11736: 11629: 11573:(e.g. to cross the same 11568: 11562: 11459: 11418:of an object within the 11391: 11385: 10739:orbit with little or no 10564:electromagnetic spectrum 10486: 10444:quadratic field strength 9958:The scientific study of 9594: 9277: 9201:, is commonly used as a 9037:The tilt of an object's 8891:curved trajectory of an 8879: 8815: 8448: 8438: 8412: 8307: 8168: 7892: 7825:moment of inertia factor 7739: 7665: 7312: 7151:is a main-sequence star. 7146: 6944: 6900: 6753: 6679:to be visible along the 6513: 6067: 5617: 5580: 5554: 4774: 4715:about the center of the 4432:electromagnetic spectrum 4393: 4332: 4277: 4130: 4031:that exists outside the 3818: 3662: 3655: 3621: 3448: 3343: 3223: 3135: 2711: 2588: 2490: 2454: 2230: 2221: 2217:electromagnetic spectrum 1972: 1932: 1725: 1361: 1238:The scientific study of 753: 718:recognizable in Earth's 697: 498: 396: 369:chemically peculiar star 266:electromagnetic spectrum 17085:Astronomy-related lists 16819:Artificial intelligence 16553:Astrology and astronomy 16263:Gravitational radiation 15887:"Astronomical Glossary" 15773:2003A&A...401..997P 15689:2011A&A...528A..27H 15638:Sanders, Jason (2015), 15440:1986A&A...165..135R 15340:1981A&A....99..126H 15072:1982A&AS...48..503R 14920:2017A&A...597A..29S 14631:, Infobase Publishing, 14522:2009A&A...493.1099S 14439:Walker, Gordon (1987), 14259:hydrostatic equilibrium 14178:active galactic nucleus 13678:across the face of the 13040:synodic rotation period 12872:supermassive black hole 12712:submillimetre astronomy 12628:stellar evolution model 12536:spectral classification 12281: 12185:observational astronomy 12079:spectral classification 11534:small Solar System body 11143:gravitational potential 11141:that orbits within the 11013:Rosseland optical depth 10990:directly rather than a 10559:supermassive black hole 10541:active galactic nucleus 10461:magnetic field strength 9867:hydrostatic equilibrium 9257:, in which the bodies' 9086:intersects a specified 8726:observational astronomy 8630:stellar classifications 8484:observational astronomy 8281:small Solar System body 8264:small Solar System body 8261:, or sometimes another 8037:and the east direction. 7924:minor natural satellite 7859: 7841: 7377:by French comet hunter 7135:hydrostatic equilibrium 6673:Moon's elliptical orbit 6518:. It is similar to the 6010:), especially chemical 5885:Gamma Doradus variables 5455:observational astronomy 4930:group of galaxies (GrG) 4757:galactocentric distance 4653:active galactic nucleus 4641:supermassive black hole 4565:supermassive black hole 4495:extragalactic astronomy 4398:, as well as all other 3993:extragalactic astronomy 3085:trans-Neptunian objects 3044:distant detached object 2921:observational astronomy 2360:compact stellar nucleus 2146:, after correction for 2085:compact stellar nucleus 2079:supermassive black hole 2002:small Solar System body 1346:Earth's rotational axis 702:, as viewed from Earth. 246:active galactic nucleus 17049:Structural engineering 16989:Mechanical engineering 16962:Western and South Asia 16472:Hubble Space Telescope 14408:Maeder, Andre (2008), 14239:zero-age main sequence 14082:stellar classification 14015:statistical dispersion 13877:UBV photometric system 13824:cosmic distance ladder 13799:empirical relationship 13694:can be used to detect 13644:trans-Neptunian object 13639: 13266:telluric contamination 12810: 12805:planetary-mass objects 12658:stellar magnetic field 12542:The categorization of 12528:stellar classification 12154: 12088:stellar classification 11957:is distinguished from 11594:not perfectly circular 11487: 11201:atmospheric refraction 11147:Large Magellanic Cloud 11020:extinction coefficient 10837: 10520: 10450:stellar magnetic field 10389:pre-main-sequence star 10056:, among other objects. 9950:Also sometimes called 9644:atmospheric resistance 9450: 9305: 9141:takes to complete one 9027: 9020:(yellow) intersects a 8407:, which are a type of 7704: 6991: 6889:astronomical magnitude 6633:Lenakaeia Supercluster 6171:interstellar reddening 5901:hydrogen burning limit 5442: 5399:gravitational collapse 5185:diffusively scattering 4697:takes to complete one 3952: 3606: 3527:with an approximately 3425: 3372:. It differs from the 3366:bodies within various 2983:gravitational collapse 2829: 2826:Hubble Space Telescope 2518:cosmic distance ladder 2355:with very small radii. 2064:central massive object 1983:. It is the basis for 1853: 1581:for the origin of the 1499: 1192:astronomical constants 1055:astronomical catalogue 559:argument of pericenter 341: 264:over some part of the 125: 122: 119: 116: 113: 110: 107: 104: 101: 98: 95: 92: 89: 86: 83: 80: 77: 74: 71: 68: 65: 62: 59: 56: 53: 50: 17075:Glossaries of science 16914:Environmental science 16799:Aerospace engineering 16576:Astroparticle physics 16311:Australian Aboriginal 15615:John Wiley & Sons 15024:Ridpath, Ian (2007), 14842:"Section M: Glossary" 14751:Ridpath, Ian (2012), 14356:Modern constellations 14313:Zodiac constellations 13930:, all other forms of 13889:Johnson–Morgan system 13792:Tully–Fisher relation 13629: 13539:Tisserand's parameter 13389:thick disk population 13360:thick disk population 13349:theoretical astronomy 13219:The component of the 13015:equal to the average 12802:, as well as certain 12143: 11080:rotational modulation 10981:planetary-mass object 10827: 10697:main-sequence turnoff 10509: 10233:gravitational primary 10061:planetary-mass object 9996:objects in or out of 9890:planetary-mass object 9500:partial solar eclipse 9467:shift of exactly one 9434: 9380:orbital state vectors 9294: 9193:Earth's orbital plane 9005: 8752:theoretical astronomy 8422:New General Catalogue 7879:on Earth; because of 7679: 6981: 6625:Laniakea Supercluster 6591:Coriolis acceleration 6464:Edgeworth–Kuiper belt 6267:following a distant, 5647:effective temperature 5429: 5421:gravitational lensing 5276:Artificial satellites 3942: 3826:plane of the ecliptic 3715:perpendicular to its 3673:celestial coordinates 3651:artificial satellites 3596: 3498:effective temperature 3460:plane of the ecliptic 3395:plane of the ecliptic 3390: 3328:plane of the ecliptic 2815: 2479:coronal mass ejection 2393:have either the same 2304:gravitationally bound 2088:, but sometimes both. 2076:, typically either a 2038:cis-Neptunian objects 2017:between those of the 1900:artificial satellites 1819: 1719:and by the fusion of 1483: 1047:astronomical "object" 905:, among other topics. 899:extraterrestrial life 795:distant minor planets 555:argument of perifocus 547:argument of periapsis 476:visual brightness (V) 324: 21:glossary of astronomy 16568:Astronomers Monument 16500:Very Large Telescope 16047:Astronomical symbols 15963:, Harvard University 14697:Astronomical Almanac 14336:Outline of astronomy 14215: 14149: 14064: 13973: 13869: 13665:across a particular 13482:. An example is the 13467:orbital eccentricity 13369:thin disk population 13208: 12979:, which is equal to 12752:artificial satellite 12726:astronomical objects 12486:Of or relating to a 12377:Any small number of 12309:thermonuclear fusion 12289:A massive, luminous 12176:positional astronomy 12097:spectroscopic binary 11997:, released from the 11687:magnetic field lines 11509:. In the context of 11135:A smaller companion 11108: 10917:circumplanetary disk 10748:orbital eccentricity 10632:astronomical objects 10611:Beta Cephei variable 10601:Doppler spectroscopy 10586: 10550:is generated by the 10437: 10300:projected separation 10102:protoplanetary disks 9935:. An example is the 9869:and therefore has a 9834:Of or relating to a 9808:thermonuclear fusion 9572:artificial satellite 9514:cataclysmic variable 9425: 9195:, which defines the 8966:orbital eccentricity 8734:astronomical objects 8584: 8536:nuclear star cluster 8135: 8093:astronomical objects 8056:A loose grouping of 7930:An especially small 7732:An object in direct 7434:through the Earth's 7368:astronomical objects 7127:, in particular the 6995: 6583:gravitational forces 6538: 6390: 6333: 6317:that represents the 6114:astronomical objects 5967: 5650:for a population of 5535:and in star-forming 5494: 5323:geostationary orbits 5284:geosynchronous orbit 5254:geosynchronous orbit 5019:astronomical objects 4764:gravitational center 4468: 4371:astronomical objects 4368:The "background" of 4346:First Point of Aries 4304:The location of the 4299:First Point of Libra 4291:First Point of Libra 4243:The location of the 4228:First Point of Aries 4214:first magnitude star 4177:that lies along the 4171:A randomly situated 4127:magnetic field lines 4100: 4074:outside the Earth's 3645:astronomical objects 3571:orbital eccentricity 3307:orbital eccentricity 3273: 3257:as well as low-mass 2780: 2593:or from outside the 2507:or present during a 2501:, often following a 2386:astronomical objects 2369:nuclear star cluster 2282:common proper motion 2134:is the ratio of the 1876:astronomical objects 1767:reflecting telescope 1736: 1474: 1297:chemical composition 1280:astronomical objects 1137:astronomical objects 1063:astronomical catalog 969:spectroscopic binary 696:with respect to the 594:artificial satellite 452:artificial satellite 148: 16641:List of astronomers 16054:Astronomical object 15826:2004ApJ...612..724Y 15367:2009MNRAS.394.1338B 15216:2005ASPC..335....3S 15177:1981PASP...93..681M 15006:1978IAUS...79...51E 14965:2019ApJ...871..227F 14883:1964SvA.....7..618C 14722:John Wiley and Sons 14665:2010ApJS..187..228S 14596:2004MNRAS.350..189T 14480:1984ApJ...279..763N 14169:A seemingly normal 14124:Wilson–Bappu effect 14101:composed mostly of 14008:velocity dispersion 13953:observable universe 13634:total solar eclipse 13619:total solar eclipse 13552:Tisserand parameter 13313:interstellar medium 13304:, beyond which the 13223:of a star or other 13215:tangential velocity 12777:astronomical object 12731:terahertz radiation 12571:stellar designation 12476:Orion constellation 12168:spherical astronomy 11954:apparent solar time 11741:, or approximately 11555:on Earth, i.e. the 11122:total solar eclipse 10960:interstellar planet 10742:orbital inclination 10695:. It begins at the 10660:astronomical object 10476:ecliptic longitudes 10373:protoplanetary disk 10353:protoplanetary disk 10133:Another name for a 9393:Also simply called 9347:origin of longitude 9138:astronomical object 9032:orbital inclination 8746:observable universe 8717:observable universe 8621:A group of massive 8516:orbital inclination 8331:astronomical object 8108:gravitational waves 8050:stellar association 7237:The fraction of an 7098:astronomical object 6871:astronomical object 6819:origin of longitude 6617:man-made satellites 6136:interstellar medium 6044:orbital inclination 5875:This is a class of 5811:containing Earth's 5732:astronomical object 5607:interstellar medium 5464:gravitational waves 5388:. They differ from 5228:geostationary orbit 5208:center of the Earth 5081:composed mainly of 5005:gamma-ray astronomy 4899:and other types of 4868:observable universe 4773:. For example, the 4739:gravitational field 4688:astronomical object 4503:galactic anticenter 4273:ecliptic coordinate 4221:apparent magnitudes 4113:A bright spot on a 4028:astronomical object 3977:astronomical object 3947:evolutionary tracks 3847:, occur on or near 3685:astronomical object 3540:lenticular galaxies 3131:astronomical object 2958:A star composed of 2903:astronomical object 2824:as detected by the 2774:time of culmination 2707:astronomical object 1986:spherical astronomy 1858:celestial mechanics 1623:optical double star 1584:observable universe 1436:orbital inclination 1302:celestial mechanics 1129:astronomical symbol 1091:observable universe 1074:astronomical object 1017:observable universe 306:diffusely reflected 176:the mass of the Sun 167:system, a class of 37:atmosphere of Earth 16627:Physical cosmology 14284:celestial latitude 14047:Local Supercluster 14038:Virgo Supercluster 13999:or its profile of 13697:extrasolar planets 13640: 13638:as seen from Earth 13411:tidal acceleration 13270:Earth's atmosphere 13058:) relative to the 12647:model of a star's 12603:2. The 12597:stellar atmosphere 12503:stellar atmosphere 12196:spherical geometry 12155: 12018:geomagnetic storms 11908:natural satellites 11233:tidal acceleration 10838: 10663:that emits strong 10521: 10317:astronomical units 10306:angular separation 10209:general relativity 10201:Apsidal precession 9709:plane of reference 9691:photometric system 9480:astronomical units 9451: 9306: 9232:orbital parameters 9204:plane of reference 9113:non-inclined orbit 9089:plane of reference 9052:plane of reference 9028: 8959:frame of reference 8510:plane of reference 8492:non-inclined orbit 8409:subatomic particle 8337:interstellar cloud 7818:molecular hydrogen 7813:interstellar cloud 7705: 7622:1. The 7327:meridian astronomy 6992: 6986:phases of the Moon 6837:plane of reference 6685:of the lunar disk. 6637:Local Supercluster 6473:circumstellar disc 6421:The motion of one 6349:interstellar cloud 6326:evolutionary track 6100:infrared astronomy 5940:satellite galaxies 5895:instability strips 5659:absolute magnitude 5538:irregular galaxies 5443: 5434:gravitational lens 5408:gravitational lens 5195:geometric position 4877:, are much larger. 4562:, consisting of a 4476:galactic astronomy 4206:astronomical image 4012:galactic astronomy 3953: 3907:evolutionary track 3723:geographical poles 3618:angular separation 3607: 3426: 3260:substellar objects 3014:plane of reference 2876:circumstellar disc 2830: 2796:circumstellar disc 2674:circumstellar disc 2402:ecliptic longitude 2180:circumstellar disk 2172:circumstellar disc 1908:celestial meridian 1854: 1837:plane of its orbit 1753:coudé spectrograph 1578:cosmological model 1500: 1224:10 parsecs; 1.5813 1155:phases of the Moon 948:astrometric binary 894:extrasolar planets 848:main asteroid belt 811:circumstellar disc 684:The position of a 647:plane of reference 565:The angle from an 468:apparent magnitude 342: 198:apparent magnitude 184:absolute magnitude 17062: 17061: 17044:Scientific naming 17034:Quantum computing 16864:Computer hardware 16859:Clinical research 16854:Civil engineering 16749: 16748: 16634:Quantum cosmology 16620:Planetary geology 16413: 16412: 16124:Celestial subject 15250:Mineola, New York 14395:978-0-521-82364-7 14228:The point in the 14117:Type Ia supernova 14023:or galaxies in a 13853:nautical twilight 13772:eccentric anomaly 13374:The layer of the 13281:termination shock 13226:astronomical body 13018:rotational period 12992:synchronous orbit 12960:astronomical body 12936:stages or when a 12760:substellar object 12650:stellar evolution 12620:stellar evolution 12548:based upon their 12404:planetary systems 12328:emission spectrum 12261:centrifugal force 11963:. Solar time and 11849:geomagnetic storm 11643:precisely aligned 11600:not perpendicular 11327:celestial equator 11318:southward equinox 11310:September equinox 10999:substellar object 10900:satellite systems 10888:astronomical body 10860:celestial equator 10857:. It divides the 10792:retrograde motion 10730:natural satellite 10637:radio frequencies 10403:, this is a near 10292:retrograde motion 9973:planetary systems 9944:planetary science 9790:astronomical body 9300:orbital resonance 9218:orbital resonance 9182:astronomical body 9135:The time a given 9129:revolution period 9060:orbital mechanics 8918:elliptical orbits 8912:natural satellite 8768:astronomical body 8565:astronomical body 8519:is 0 degrees for 8507:with a specified 8460:celestial objects 8272:near-Earth object 8240:astronomical body 8223:natural satellite 8176:The point on the 8160:giant ellipticals 8001:MK classification 7958:minor-planet moon 7933:natural satellite 7870:natural satellite 7853:natural satellite 7775:natural satellite 7767:minor-planet moon 7297:orbital resonance 7216:September equinox 7191:celestial equator 7182:Northward equinox 7012:astronomical body 6895:visual brightness 6611:trojan satellites 6587:centripetal force 6341:Jeans instability 6264:natural satellite 5947:) as well as its 5852:celestial equator 5792:celestial equator 5305:rotational period 5302:equal to Earth's 5293:synchronous orbit 5145:geocentric zenith 4896:galactic clusters 4785:(approximately 8 4685:The time a given 4428:magnetic activity 4340:celestial equator 4322:. Located in the 4307:September equinox 4285:celestial equator 4261:. Located in the 4054:extrasolar planet 4020:extrasolar object 3772:primary direction 3766:celestial equator 3749:fundamental plane 3728:celestial equator 3516:elliptical galaxy 3466:primary direction 3455:fundamental plane 3375:celestial equator 3228:, in contrast to 3152:) around the two 2960:degenerate matter 2852:celestial equator 2770:lower culmination 2760:upper culmination 2681:break-up velocity 2669:Newtonian gravity 2665:centrifugal force 2657:break-up velocity 2650:critical velocity 2643:critical rotation 2431:in 1930. Compare 2328:astronomical body 2107:magnetic activity 1943:"intersects" the 1869:that studies the 1830:celestial equator 1801:. Due to Earth's 1774:celestial equator 1696:substellar object 1681:Newtonian gravity 1677:centrifugal force 1669:critical rotation 1663:critical velocity 1654:break-up velocity 1351:its orbital plane 1335:astronomical body 1241:celestial objects 1200:astronomical unit 1097:astronomical body 1000:astronomical body 936:planetary geology 919:orbital mechanics 615:natural satellite 539:elliptical orbits 295:astronomical body 33:celestial objects 17092: 16869:Computer science 16776: 16769: 16762: 16753: 16752: 16742: 16738: 16737: 16730: 16726: 16725: 16710: 16701: 16694: 16687: 16680: 16671: 16664: 16657: 16655:Medieval Islamic 16650: 16643: 16636: 16629: 16622: 16615: 16608: 16599: 16592: 16585: 16578: 16571: 16562: 16555: 16548: 16541: 16539:Astroinformatics 16534: 16527: 16520: 16518:Archaeoastronomy 16502: 16495: 16488: 16481: 16479:Keck Observatory 16474: 16467: 16460: 16453: 16446: 16439: 16432: 16406: 16397: 16390: 16383: 16376: 16374:Medieval Islamic 16369: 16362: 16355: 16348: 16341: 16334: 16327: 16320: 16313: 16293: 16286: 16279: 16272: 16265: 16258: 16251: 16233: 16224: 16217: 16210: 16203: 16201: 16193: 16191: 16179: 16172: 16152: 16145: 16138: 16116: 16109: 16102: 16095: 16082: 16081: 16070: 16063: 16056: 16049: 16042: 16033: 16026: 16019: 15998: 15991: 15984: 15975: 15974: 15970: 15969: 15968: 15952: 15951: 15950: 15934: 15933: 15932: 15916: 15915: 15914: 15900: 15899: 15898: 15873: 15872: 15852: 15846: 15845: 15819: 15817:astro-ph/0401117 15799: 15793: 15792: 15766: 15764:astro-ph/0301637 15746: 15740: 15739: 15715: 15709: 15708: 15682: 15662: 15656: 15655: 15635: 15629: 15628: 15604: 15598: 15597: 15596: 15595: 15576: 15570: 15569: 15550: 15544: 15543: 15523: 15517: 15516: 15514: 15513: 15500: 15494: 15493: 15491: 15490: 15477: 15471: 15470: 15450: 15444: 15443: 15434:(1–2): 135–156, 15422: 15416: 15415: 15395: 15389: 15388: 15378: 15361:(3): 1338–1350, 15350: 15344: 15343: 15323: 15317: 15316: 15296: 15290: 15289: 15269: 15263: 15262: 15241: 15235: 15234: 15231:The Binary Stars 15226: 15220: 15219: 15203: 15197: 15196: 15160: 15154: 15153: 15152: 15150: 15134: 15128: 15127: 15126: 15124: 15108: 15102: 15101: 15082: 15076: 15075: 15055: 15049: 15048: 15021: 15010: 15009: 14993: 14987: 14986: 14976: 14958: 14938: 14932: 14931: 14913: 14893: 14887: 14886: 14871:Soviet Astronomy 14866: 14860: 14859: 14858: 14857: 14838: 14803: 14802: 14801: 14800: 14785: 14779: 14778: 14776: 14775: 14748: 14742: 14741: 14739: 14738: 14711: 14705: 14704: 14703:, 2008, Glossary 14693: 14687: 14686: 14676: 14648: 14642: 14641: 14624: 14618: 14617: 14607: 14589: 14587:astro-ph/0312113 14569: 14563: 14562: 14542: 14536: 14535: 14533: 14516:(3): 1099–1107, 14507: 14498: 14492: 14491: 14463: 14457: 14456: 14436: 14430: 14429: 14405: 14399: 14398: 14379: 14309: 14303: 14302:celestial sphere 14297: 14291: 14285: 14279: 14275:The area of the 14255: 14249: 14232: 14179: 14173: 14166: 14143: 14139:of the emitting 14137: 14113: 14099: 14083: 14058: 14027: 14026:galactic cluster 14021: 14020:globular cluster 13997: 13990: 13967: 13954: 13928: 13922: 13916: 13892: 13861:two-body problem 13854: 13848: 13842: 13825: 13815:angular velocity 13811: 13805: 13785: 13784:orbital elements 13779: 13773: 13763: 13762:elliptical orbit 13757: 13748: 13744: 13740: 13710: 13704: 13698: 13688: 13682: 13676:transit of Venus 13669: 13663: 13662:celestial object 13635: 13604: 13598: 13592: 13586: 13585:orbital elements 13580: 13574: 13568: 13562: 13555: 13544: 13532: 13526: 13512: 13506: 13500: 13486: 13480: 13474: 13468: 13462:angular momentum 13458: 13433: 13427: 13426:rotation periods 13421: 13414: 13396: 13390: 13384: 13378: 13342: 13336: 13330: 13314: 13308: 13302: 13296: 13290: 13262: 13239: 13233: 13227: 13192: 13186: 13180: 13174: 13158: 13148: 13142: 13136: 13130: 13129:celestial sphere 13124: 13123:background stars 13108: 13102: 13096: 13090: 13084: 13078: 13068: 13062: 13056: 13050: 13043: 13025: 13019: 13013: 13007: 13001: 12986: 12984: 12977: 12976:standard gravity 12967: 12961: 12940: 12934: 12928: 12922: 12916: 12900: 12894: 12888: 12882: 12864: 12853: 12840: 12806: 12800: 12799:stellar remnants 12794: 12788: 12778: 12771: 12753: 12747: 12727: 12721: 12717:The subfield of 12694:stellar parallax 12687: 12681: 12675: 12651: 12645: 12638: 12613: 12607: 12598: 12589:stellar envelope 12580:stellar dynamics 12564: 12558: 12552: 12546: 12539: 12521: 12514: 12511:stellar envelope 12496: 12490: 12464: 12463:celestial sphere 12458: 12452: 12433: 12424:starburst galaxy 12417: 12411: 12407:, which include 12405: 12399: 12393: 12387: 12381: 12374: 12347: 12329: 12323: 12305: 12278: 12276: 12270: 12268: 12248: 12237: 12228: 12218:standard gravity 12202: 12192: 12191:celestial sphere 12186: 12179: 12150: 12126: 12112: 12106: 12089: 12072: 12065: 12059: 12053: 12047: 12041: 12025: 12019: 12013: 12007: 12001: 11973: 11967: 11961: 11955: 11949: 11943: 11937: 11931: 11925: 11909: 11903: 11897: 11891: 11885: 11879: 11873: 11867: 11866:planetary system 11850: 11833: 11823: 11817: 11793: 11787: 11781: 11775: 11766:solar prominence 11759: 11754: 11749: 11746: 11739: 11693: 11679: 11663: 11657: 11651: 11644: 11638: 11632: 11626: 11610: 11601: 11595: 11589: 11583: 11577: 11571: 11565: 11559: 11553: 11526: 11519: 11518:celestial sphere 11513: 11507: 11499:, including the 11474: 11468: 11462: 11456: 11450: 11434: 11433:celestial sphere 11428: 11422: 11416: 11400: 11394: 11388: 11382: 11381:celestial sphere 11376: 11370: 11353: 11342:autumnal equinox 11334: 11328: 11321: 11303: 11299:, such as for a 11297: 11292: 11281: 11253: 11239: 11207: 11193: 11187: 11180: 11153: 11139: 11130:satellite galaxy 11123: 11102:BY Dra variables 11094: 11088: 11074: 11068: 11062: 11061:background stars 11058:relative to the 11056: 11055:axis of rotation 11039: 11032: 11026: 11006: 11005:planetary system 11000: 10994: 10988: 10982: 10975: 10941: 10935: 10918: 10907: 10901: 10895: 10889: 10883: 10877: 10861: 10851: 10833: 10818: 10811: 10801: 10772:relativistic jet 10765: 10761:, as opposed to 10759: 10749: 10743: 10737: 10731: 10693: 10692:globular cluster 10687: 10678:red-giant branch 10671: 10661: 10645:radio telescopes 10633: 10627: 10623:The subfield of 10607: 10560: 10554: 10548: 10542: 10535: 10515: 10501: 10495: 10489: 10483: 10477: 10454:root mean square 10431: 10425: 10366: 10360: 10354: 10348: 10324:of the observer. 10318: 10312: 10293: 10286: 10276: 10269: 10251: 10244: 10197: 10191: 10190:axis of rotation 10175: 10169: 10159: 10143: 10137: 10121: 10115: 10109: 10103: 10093: 10077: 10054: 10048: 10042: 10036: 10030: 10024: 10018: 10012: 10006: 10000: 9994: 9981:planetary system 9974: 9968: 9962: 9955: 9933: 9927: 9914:planetary nebula 9897: 9891: 9885: 9879: 9873: 9863: 9856: 9853:planetary object 9838: 9820: 9814: 9796: 9791: 9775: 9767:plane of the sky 9761: 9760:equatorial plane 9755: 9754:invariable plane 9749: 9743: 9737: 9731: 9730:orbital elements 9720: 9676: 9675:superior planets 9666: 9665:Inferior planets 9660: 9639: 9638:two-body problem 9633: 9627: 9621: 9604: 9597: 9580: 9573: 9567: 9550: 9543: 9536: 9481: 9477:or 206,265 9475: 9465: 9447: 9440: 9419: 9409: 9408:celestial bodies 9398: 9376: 9370: 9364: 9355:osculating orbit 9341: 9335: 9329: 9323: 9301: 9286: 9280: 9267: 9261: 9251: 9245: 9239: 9233: 9227: 9211: 9205: 9199: 9189: 9183: 9177: 9157: 9151: 9145: 9139: 9132: 9114: 9108: 9102: 9096: 9090: 9084: 9078: 9053: 9047: 9041: 9024: 9018: 9011: 9010:orbital elements 8997: 8988:orbital elements 8981: 8980:elliptical orbit 8975: 8955: 8949: 8942: 8925: 8921:around a common 8919: 8913: 8907: 8901: 8895: 8864: 8834: 8828:inner Oort cloud 8824: 8818: 8812: 8805: 8787: 8781: 8775: 8769: 8753: 8749:, as opposed to 8747: 8741: 8737:with the use of 8735: 8710: 8704: 8698: 8692: 8686: 8680: 8674: 8667: 8648: 8631: 8625: 8605:scientific model 8578: 8572: 8571:axis of rotation 8566: 8529: 8523: 8517: 8513:, such that the 8511: 8501: 8485: 8479: 8473: 8467: 8461: 8451: 8441: 8415: 8401: 8374: 8368: 8362: 8344: 8338: 8332: 8316: 8315:closest approach 8310: 8304: 8294: 8288: 8282: 8265: 8259: 8253: 8247: 8241: 8234: 8214: 8192: 8186: 8180: 8179:celestial sphere 8152:Seyfert galaxies 8120: 8114: 8100: 8094: 8088: 8072: 8066: 8060: 8053: 8035: 8029: 8022: 8004: 7985: 7967: 7959: 7952: 7946: 7940: 7934: 7927: 7901: 7895: 7889: 7883: 7877: 7871: 7854: 7836: 7814: 7797: 7789: 7782: 7776: 7760: 7754: 7748: 7742: 7736: 7719: 7698: 7691: 7690:Milky Way Galaxy 7684: 7668: 7662: 7655: 7649: 7643: 7637: 7631: 7626: 7610: 7604: 7598: 7584: 7578: 7562: 7548: 7514: 7508: 7502: 7496: 7480: 7474: 7458: 7438: 7432: 7426: 7420: 7414: 7407: 7385: 7384:deep-sky objects 7375: 7369: 7353: 7347: 7341: 7335: 7321: 7315: 7298: 7283: 7282:two-body problem 7277: 7271: 7265: 7259: 7253: 7247: 7241: 7240:elliptical orbit 7232: 7217: 7210:autumnal equinox 7198: 7192: 7185: 7166: 7149: 7131: 7125: 7119: 7099: 7079: 7073: 7067: 7051: 7045: 7039: 7033: 7027: 7026:planetary system 7013: 6987: 6973: 6967: 6953: 6952:constantly faces 6947: 6941: 6935: 6928: 6910: 6896: 6890: 6872: 6866: 6860: 6844: 6843:orbital elements 6838: 6832: 6826: 6820: 6794: 6793:elliptical orbit 6788: 6782: 6776: 6756: 6740: 6734: 6728: 6723: 6721: 6715: 6713: 6706: 6700: 6669: 6644: 6618: 6612: 6578: 6572: 6565: 6546:Lagrangian point 6528: 6522: 6516: 6510: 6504: 6498: 6492: 6486: 6480: 6474: 6467: 6449: 6443: 6425: 6418: 6384: 6378: 6372: 6350: 6327: 6321: 6315: 6295: 6289: 6285:orbit about its 6283: 6277: 6271: 6265: 6247:irregular galaxy 6231: 6225:angular momentum 6221: 6220:planetary system 6215: 6208: 6193:invariable plane 6186: 6180: 6156: 6150: 6115: 6109: 6105:The subfield of 6089: 6088:superior planets 6079: 6070: 6045: 6028: 6014: 5984: 5957: 5951: 5941: 5935: 5921: 5915: 5909: 5891: 5865: 5859: 5853: 5847: 5827: 5821: 5815: 5805: 5799: 5793: 5787: 5786:celestial sphere 5781: 5780:celestial object 5765: 5745: 5739: 5733: 5726: 5708: 5702: 5696: 5690: 5684: 5678: 5672: 5666: 5660: 5654: 5648: 5642: 5626: 5620: 5614: 5608: 5583: 5577: 5576:geometric center 5557: 5551:geometric center 5539: 5533: 5511: 5488: 5482: 5476: 5470: 5456: 5435: 5417: 5416:galactic cluster 5392: 5386: 5380: 5374: 5368: 5359:globular cluster 5352: 5346: 5340: 5324: 5318: 5312: 5306: 5300: 5294: 5277: 5271:Earth's rotation 5267: 5261: 5255: 5250: 5243: 5221: 5215: 5209: 5203: 5181: 5172:geometric albedo 5165: 5159: 5153: 5152:celestial sphere 5135: 5134:geometric center 5115:geometric center 5101: 5079: 5063: 5057: 5051: 5045: 5020: 5014: 5010:The subfield of 4974: 4958: 4952: 4946: 4945:Milky Way Galaxy 4940: 4933: 4915: 4909: 4903: 4897: 4891: 4875: 4869: 4863: 4857: 4851: 4845: 4839: 4833: 4827: 4826:interstellar gas 4821: 4820:stellar remnants 4815: 4799: 4793: 4789:) away from the 4783: 4779:is about 27,000 4777: 4771: 4767:of a particular 4765: 4751: 4745: 4735: 4719: 4713: 4707: 4701: 4695: 4689: 4682: 4660: 4654: 4648: 4642: 4636: 4629: 4614:galactic nucleus 4578: 4572: 4566: 4560: 4555: 4549: 4530: 4524: 4523:celestial sphere 4518: 4517:Milky Way Galaxy 4512: 4496: 4490: 4485: 4462: 4446: 4424: 4408: 4407:deep-sky objects 4402: 4396: 4390: 4384: 4378: 4372: 4365: 4362:background stars 4347: 4341: 4335: 4326: 4320: 4314: 4313:celestial sphere 4308: 4292: 4286: 4280: 4274: 4265: 4259: 4253: 4252:celestial sphere 4247: 4240: 4207: 4201: 4185: 4175: 4161: 4145: 4139: 4133: 4123: 4117: 4093: 4078: 4072: 4065: 4047: 4041: 4035: 4029: 4013: 4007: 4002: 3978: 3948: 3934: 3928: 3922: 3918:that a solitary 3916: 3900: 3870: 3863: 3857: 3851: 3845: 3844:autumnal equinox 3839: 3833: 3827: 3821: 3815: 3809: 3793: 3779: 3773: 3767: 3761: 3760:celestial sphere 3755: 3745: 3729: 3719: 3718:axis of rotation 3709: 3692: 3686: 3680: 3679:orbital elements 3674: 3658: 3652: 3646: 3630: 3624: 3602: 3601:elliptical orbit 3584: 3578: 3572: 3566: 3559: 3548:elliptical orbit 3541: 3535: 3525: 3491: 3485: 3479: 3473: 3467: 3461: 3453:or the Earth, a 3451: 3445: 3439: 3422: 3415: 3409: 3403: 3402:celestial sphere 3396: 3382: 3376: 3370: 3364: 3358: 3352: 3351:celestial sphere 3346: 3331: 3308: 3290: 3267: 3261: 3255: 3249: 3248:stellar remnants 3232: 3226: 3220: 3214: 3189: 3182: 3162: 3156: 3150: 3144: 3138: 3132: 3115: 3098: 3092: 3086: 3076: 3070: 3064: 3058: 3051: 3028: 3021: 3015: 3009: 3002: 2984: 2978: 2972: 2966: 2946: 2940: 2934: 2928: 2922: 2916: 2910: 2904: 2883: 2877: 2860: 2853: 2843: 2821: 2803: 2797: 2766: 2756: 2755:celestial sphere 2750: 2744: 2738: 2732: 2726: 2720: 2714: 2708: 2701: 2698:meridian transit 2682: 2675: 2660: 2637: 2613: 2597: 2591: 2567: 2548: 2544:which exists in 2538: 2511: 2510:solar prominence 2505: 2499: 2493: 2463: 2457: 2436: 2429: 2419: 2418:celestial sphere 2415:A region on the 2403: 2397: 2387: 2370: 2353: 2352:stellar remnants 2347: 2341: 2335: 2329: 2322: 2300: 2294: 2261: 2252:commensurability 2233: 2183: 2166: 2136:equivalent width 2133: 2124: 2113: 2086: 2080: 2074: 2057: 2051: 2045: 2039: 2033: 2027: 2021: 2015: 2009: 2003: 1987: 1981: 1980:background stars 1975: 1966:celestial sphere 1959: 1953: 1947: 1946:celestial sphere 1941: 1940:axis of rotation 1935: 1918: 1901: 1895: 1889: 1883: 1877: 1873:of all types of 1867: 1850: 1844: 1838: 1831: 1824: 1823:axis of rotation 1811: 1805: 1799: 1793: 1787: 1786:celestial sphere 1717: 1711: 1697: 1672: 1664: 1639: 1619: 1613: 1607: 1601: 1585: 1579: 1549: 1543: 1537: 1536:planetary system 1527: 1526:elliptical orbit 1517: 1496: 1489: 1444:axis of rotation 1437: 1427: 1421: 1415: 1408: 1390: 1384: 1374: 1368:equatorial bulge 1364: 1358: 1352: 1348:with respect to 1342: 1341:axis of rotation 1336: 1330: 1321:axial precession 1303: 1281: 1255:astrophotography 1248: 1242: 1228:10 light-years). 1227: 1223: 1210: 1193: 1179: 1173: 1167: 1162: 1156: 1150: 1144: 1138: 1122: 1116: 1110: 1104: 1103:planetary system 1098: 1092: 1085: 1082:celestial object 1066: 1048: 1042: 1036: 1030: 1024: 1018: 1011: 993: 992:celestial bodies 987: 970: 963: 957: 939: 920: 895: 877: 870: 844: 838: 832: 818: 812: 796: 790: 784: 778: 772: 766: 756: 750: 744: 728: 722: 716: 700: 694: 688: 673: 666: 660: 654: 648: 642: 635: 616: 609: 603: 587: 586:orbital elements 581: 575: 569: 562: 540: 534: 528: 522: 516: 510: 479: 460: 453: 447: 430: 423: 406: 399: 382: 375: 355: 333: 312: 302: 296: 272: 262: 256: 239: 233: 227: 211: 205: 199: 193: 177: 171: 165: 17100: 17099: 17095: 17094: 17093: 17091: 17090: 17089: 17065: 17064: 17063: 17058: 16957:Hebrew toponyms 16952:Arabic toponyms 16790: 16780: 16750: 16745: 16733: 16721: 16713: 16706: 16697: 16690: 16685:X-ray telescope 16683: 16676: 16667: 16660: 16653: 16646: 16639: 16632: 16625: 16618: 16611: 16604: 16595: 16588: 16581: 16574: 16565: 16558: 16551: 16544: 16537: 16530: 16523: 16516: 16505: 16498: 16491: 16484: 16477: 16470: 16463: 16456: 16449: 16442: 16435: 16428: 16420: 16409: 16402: 16393: 16386: 16379: 16372: 16365: 16358: 16351: 16344: 16337: 16330: 16323: 16316: 16309: 16296: 16291:Multi-messenger 16289: 16282: 16275: 16268: 16261: 16254: 16247: 16236: 16229: 16220: 16213: 16206: 16199: 16196: 16187: 16182: 16175: 16168: 16157: 16148: 16141: 16130: 16119: 16114:Space telescope 16112: 16105: 16098: 16091: 16073: 16066: 16059: 16052: 16045: 16038: 16029: 16022: 16015: 16007: 16002: 15966: 15964: 15955: 15948: 15946: 15937: 15930: 15928: 15925:Public Outreach 15919: 15912: 15910: 15906:Astronomy Terms 15903: 15896: 15894: 15885: 15882: 15877: 15876: 15869: 15853: 15849: 15800: 15796: 15757:(3): 997–1007, 15747: 15743: 15736: 15728:, p. 257, 15716: 15712: 15663: 15659: 15652: 15636: 15632: 15625: 15617:, p. 248, 15605: 15601: 15593: 15591: 15578: 15577: 15573: 15567: 15551: 15547: 15540: 15524: 15520: 15511: 15509: 15502: 15501: 15497: 15488: 15486: 15479: 15478: 15474: 15467: 15451: 15447: 15423: 15419: 15412: 15396: 15392: 15351: 15347: 15324: 15320: 15313: 15297: 15293: 15286: 15270: 15266: 15260: 15242: 15238: 15227: 15223: 15204: 15200: 15161: 15157: 15148: 15146: 15135: 15131: 15122: 15120: 15111:Esken, Thomas, 15109: 15105: 15099: 15083: 15079: 15056: 15052: 15038: 15022: 15013: 14994: 14990: 14939: 14935: 14894: 14890: 14867: 14863: 14855: 14853: 14840: 14839: 14806: 14798: 14796: 14787: 14786: 14782: 14773: 14771: 14769: 14761:, p. 163, 14749: 14745: 14736: 14734: 14732: 14724:, p. 110, 14712: 14708: 14695: 14694: 14690: 14649: 14645: 14639: 14625: 14621: 14570: 14566: 14559: 14543: 14539: 14505: 14499: 14495: 14464: 14460: 14453: 14437: 14433: 14426: 14406: 14402: 14396: 14380: 14369: 14364: 14332: 14322: 14272: 14242: 14225: 14218: 14192: 14157: 14152: 14142:late-type stars 14126: 14098:stellar remnant 14092: 14072: 14067: 14041: 14010: 13996:radial velocity 13983: 13976: 13901: 13879: 13872: 13863: 13834: 13794: 13750: 13746: 13742: 13738: 13728: 13719: 13656: 13647: 13621: 13611: 13546: 13542: 13528:of an orbiting 13519: 13493: 13451: 13442: 13405: 13371: 13362: 13351: 13323: 13283: 13255: 13248: 13216: 13211: 13201: 13188:in the Earth's 13167: 13117: 13055:rotation period 13034: 12994: 12982: 12980: 12950: 12947:surface gravity 12909: 12887:mass of the Sun 12875: 12863:inferior planet 12833: 12831:superior planet 12824: 12815: 12762: 12740: 12714: 12705: 12703:stellar remnant 12696: 12660: 12629: 12622: 12606:common envelope 12591: 12582: 12573: 12530: 12505: 12483: 12445: 12426: 12365: 12356: 12338: 12286: 12274: 12272: 12271:(approximately 12266: 12264: 12257:Earth's gravity 12239: 12236: 12230: 12227: 12221: 12211: 12170: 12161: 12135: 12125:radial velocity 12099: 12081: 12071:winter solstice 12064:summer solstice 12034: 11995:alpha particles 11982: 11960:mean solar time 11933:in the Earth's 11918: 11887:, and numerous 11869:of the Earth's 11860: 11842: 11810: 11808: 11805: 11768: 11747: 11744: 11742: 11732: 11730: 11727: 11715: 11706: 11672: 11634:by the Earth's 11619: 11558:rotation period 11546: 11537: 11492: 11483: 11458:in the Earth's 11443: 11409: 11407:sidereal period 11369:rotation period 11363: 11312: 11278:major semi-axis 11272: 11270:semi-major axis 11262: 11246: 11224: 11214: 11171: 11162: 11132: 11116: 11111: 11081: 11049: 11047:rotation period 11015: 10987:galactic center 10972:starless planet 10954: 10928: 10911:Rings of Saturn 10885:that orbits an 10870: 10844: 10842:right ascension 10817:prograde motion 10794: 10783: 10774: 10764:irregular moons 10724: 10715: 10680: 10670:radio astronomy 10654: 10620: 10618:radio astronomy 10596: 10594:radial velocity 10589: 10527: 10494:superior planet 10470: 10456:of a series of 10445: 10440: 10418: 10405:synchronization 10401:eccentric orbit 10396: 10384: 10375: 10341: 10331: 10301: 10260: 10258:prograde motion 10227: 10218: 10184: 10152: 10130: 10086: 10064: 9988:gravitationally 9983: 9946: 9921:emission nebula 9916: 9906: 9847: 9831: 9784: 9768: 9717:reference plane 9711: 9702: 9693: 9653: 9614: 9590: 9560: 9527: 9509: 9502: 9458: 9428: 9413:minimal gravity 9389: 9357: 9348: 9312: 9296: 9260:orbital periods 9244:semi-major axis 9220: 9173:defined by the 9171:geometric plane 9166: 9156:sidereal period 9123: 9107:descending node 9092:to which it is 9071: 9062: 9034: 9023:reference plane 8990: 8968: 8933: 8889:gravitationally 8884: 8873: 8863:molecular cloud 8857: 8843: 8802:Öpik–Oort cloud 8796: 8762: 8728: 8719: 8658: 8656:observation arc 8640: 8618: 8592: 8587: 8559: 8549: 8539: 8494: 8434: 8425: 8394: 8383: 8325: 8275: 8225: 8201: 8173: 8148:active galaxies 8143: 8138: 8129: 8081: 8065:molecular cloud 8044: 8013: 7995: 7977: 7914: 7864: 7846: 7827: 7807: 7805:molecular cloud 7769: 7729: 7718:semi-minor axis 7711: 7661:Galactic Center 7619: 7591: 7571: 7541: 7523: 7489: 7467: 7451: 7394: 7379:Charles Messier 7362: 7328: 7308: 7290: 7234: 7228: 7176: 7165:semi-major axis 7158: 7137:and undergoing 7112: 7088: 7060: 7006: 6998: 6919: 6903: 6853: 6813: 6803: 6769: 6768:line of apsides 6749: 6719: 6717: 6711: 6709: 6693: 6662: 6653: 6627: 6606: 6599: 6558:libration point 6548: 6541: 6458: 6415:Keplerian orbit 6409: 6400: 6393: 6360: 6343: 6336: 6311:A curve on the 6308: 6258: 6249: 6240: 6195: 6173: 6139: 6129: 6102: 6055: 6053:inferior planet 6037: 5977: 5970: 5950:galactic corona 5928: 5914:mass of the Sun 5902: 5877:pulsating stars 5872: 5871:hybrid pulsator 5855:. Similar to a 5846:celestial poles 5836: 5826:right ascension 5814:rotational axis 5774: 5754: 5717: 5635: 5601: 5592: 5579:of the Earth's 5570: 5553:of the Earth's 5546: 5532:spiral galaxies 5504: 5497: 5449: 5410: 5401: 5361: 5333: 5317:semi-major axis 5287: 5230: 5196: 5174: 5146: 5128: 5119:oblate spheroid 5110: 5072: 5034: 5031:gamma-ray burst 5007: 4982:Galileo Galilei 4967: 4951:galaxy clusters 4924: 4884: 4808: 4792:Galactic Center 4758: 4728: 4706:galactic center 4669: 4667:galactic period 4626:galactic center 4616: 4607: 4605:galactic corona 4598: 4545:The rotational 4542: 4540:Galactic Center 4505: 4478: 4471: 4455: 4417: 4392:other than the 4356: 4301: 4231: 4216: 4194: 4168: 4154: 4110: 4103: 4085: 4056: 4022: 3995: 3959: 3912:A curve on the 3909: 3880: 3878:escape velocity 3802: 3786: 3738: 3702: 3667: 3639: 3613: 3577:circular orbits 3550: 3518: 3500: 3432: 3378:because of the 3357:reference plane 3338:defined by the 3318: 3300: 3289:late-type stars 3283: 3281:early-type star 3276: 3222:stars like the 3207: 3198: 3175: 3158:in the Earth's 3155:celestial poles 3146:, or a distant 3125: 3114:prograde motion 3107: 3038: 3036:detached object 2993: 2991:descending node 2955: 2953:degenerate star 2897: 2894:deep-sky object 2882:Keplerian orbit 2870: 2859:right ascension 2836: 2807:infrared excess 2790: 2783: 2692: 2651: 2644: 2626: 2606: 2576: 2558: 2529: 2520: 2482: 2472: 2446: 2412: 2396:right ascension 2380: 2362: 2313: 2299:radial velocity 2283: 2260:orbital periods 2254: 2226: 2208: 2199: 2190: 2174: 2164: 2158: 2131: 2126: 2122: 2116: 2102: 2095: 2067: 2035:. Centaurs are 2032:Jupiter trojans 2029:but beyond the 2014:semi-major axis 1996: 1968: 1928: 1910: 1903:, among others. 1860: 1776: 1754: 1746: 1744:Calibrator star 1739: 1730: 1690: 1655: 1648: 1632: 1594: 1575:The prevailing 1572: 1558: 1506: 1477: 1455: 1446: 1399: 1366:on the Earth's 1323: 1312: 1266: 1257: 1235: 1225: 1221: 1203: 1131: 1076: 1057: 1002: 980: 950: 930: 912: 861: 805: 737: 712:Any pattern of 709: 681: 672:descending node 626: 596: 549: 503: 493: 470: 440: 416: 392: 364: 348: 292:received by an 290:solar radiation 285: 249: 220: 207:, or 32.6 189:A measure of a 186: 158: 151: 146: 145: 46: 17: 12: 11: 5: 17098: 17088: 17087: 17082: 17077: 17060: 17059: 17057: 17056: 17051: 17046: 17041: 17036: 17031: 17026: 17021: 17016: 17011: 17009:Nanotechnology 17006: 17001: 16996: 16991: 16986: 16981: 16979:Machine vision 16976: 16971: 16966: 16965: 16964: 16959: 16954: 16949: 16944: 16936: 16935: 16934: 16929: 16921: 16916: 16911: 16906: 16905: 16904: 16899: 16891: 16886: 16881: 16876: 16871: 16866: 16861: 16856: 16851: 16846: 16841: 16836: 16831: 16826: 16821: 16816: 16811: 16806: 16801: 16795: 16792: 16791: 16782:Glossaries of 16779: 16778: 16771: 16764: 16756: 16747: 16746: 16744: 16743: 16731: 16718: 16715: 16714: 16712: 16711: 16704: 16703: 16702: 16695: 16688: 16674: 16673: 16672: 16665: 16658: 16651: 16637: 16630: 16623: 16616: 16609: 16602: 16601: 16600: 16586: 16579: 16572: 16563: 16556: 16549: 16542: 16535: 16532:Astrochemistry 16528: 16521: 16513: 16511: 16507: 16506: 16504: 16503: 16496: 16489: 16482: 16475: 16468: 16465:Hale Telescope 16461: 16454: 16447: 16440: 16433: 16425: 16423: 16415: 16414: 16411: 16410: 16408: 16407: 16400: 16399: 16398: 16384: 16377: 16370: 16363: 16356: 16349: 16342: 16335: 16328: 16321: 16314: 16306: 16304: 16298: 16297: 16295: 16294: 16287: 16280: 16273: 16266: 16259: 16252: 16244: 16242: 16238: 16237: 16235: 16234: 16227: 16226: 16225: 16211: 16204: 16198:Visible-light 16194: 16180: 16173: 16165: 16163: 16159: 16158: 16156: 16155: 16154: 16153: 16139: 16127: 16125: 16121: 16120: 16118: 16117: 16110: 16103: 16096: 16088: 16086: 16079: 16075: 16074: 16072: 16071: 16064: 16057: 16050: 16043: 16036: 16035: 16034: 16020: 16012: 16009: 16008: 16001: 16000: 15993: 15986: 15978: 15972: 15971: 15953: 15935: 15917: 15901: 15881: 15880:External links 15878: 15875: 15874: 15867: 15847: 15834:10.1086/422802 15810:(2): 724–728, 15794: 15741: 15734: 15710: 15657: 15651:978-3319187723 15650: 15630: 15624:978-3527408962 15623: 15599: 15571: 15566:978-3863950927 15565: 15545: 15538: 15518: 15495: 15472: 15466:978-0192542618 15465: 15445: 15417: 15411:978-1139425421 15410: 15390: 15345: 15318: 15312:978-1107534209 15311: 15291: 15284: 15264: 15258: 15236: 15221: 15198: 15185:10.1086/130908 15155: 15143:TAWARIKHKHWANI 15129: 15103: 15098:978-1785461477 15097: 15077: 15050: 15036: 15011: 14988: 14933: 14888: 14861: 14804: 14793:Universe Today 14780: 14768:978-0199609055 14767: 14743: 14730: 14706: 14688: 14659:(1): 228–250, 14643: 14638:978-1438109329 14637: 14619: 14580:(1): 189–195, 14564: 14558:978-0521514897 14557: 14537: 14493: 14488:10.1086/161945 14458: 14451: 14431: 14425:978-3540769491 14424: 14400: 14394: 14366: 14365: 14363: 14360: 14359: 14358: 14353: 14348: 14343: 14338: 14331: 14328: 14327: 14326: 14323: 14320:zodiacal light 14318: 14316: 14273: 14268: 14266: 14263:nuclear fusion 14243: 14237: 14235: 14226: 14221: 14217: 14214: 14213: 14212: 14193: 14188: 14186: 14183:X-ray emission 14161:An acronym of 14158: 14155: 14151: 14148: 14147: 14146: 14127: 14122: 14120: 14107:nuclear fusion 14093: 14088: 14086: 14077:spectral lines 14073: 14071:weak-line star 14070: 14066: 14063: 14062: 14061: 14042: 14036: 14034: 14031:virial theorem 14011: 14006: 14004: 14001:spectral lines 13984: 13979: 13975: 13972: 13971: 13970: 13957: 13902: 13897: 13895: 13885:Johnson system 13880: 13875: 13871: 13868: 13867: 13866: 13864: 13859: 13857: 13835: 13830: 13828: 13795: 13790: 13788: 13751: 13733: 13731: 13729: 13724: 13722: 13720: 13715: 13713: 13692:transit method 13672: 13657: 13652: 13650: 13648: 13642: 13624: 13622: 13617: 13615: 13612: 13609: 13607: 13591:semimajor axis 13547: 13537: 13535: 13520: 13517: 13515: 13494: 13491: 13489: 13452: 13447: 13445: 13443: 13438: 13436: 13406: 13401: 13399: 13383:galactic plane 13372: 13367: 13365: 13363: 13358: 13356: 13352: 13347: 13345: 13324: 13319: 13317: 13284: 13279: 13277: 13256: 13253: 13251: 13249: 13244: 13242: 13217: 13214: 13210: 13207: 13206: 13205: 13202: 13197: 13195: 13168: 13163: 13161: 13147:orbital period 13118: 13115:synodic period 13113: 13111: 13089:orbital period 13035: 13030: 13028: 13024:same direction 13012:orbital period 12995: 12990: 12988: 12951: 12945: 12943: 12910: 12905: 12903: 12876: 12870: 12868: 12834: 12829: 12827: 12825: 12820: 12818: 12816: 12811: 12809: 12763: 12758: 12756: 12741: 12736: 12734: 12715: 12710: 12708: 12706: 12701: 12699: 12697: 12692: 12690: 12665:magnetic field 12661: 12656: 12654: 12630: 12627: 12625: 12623: 12618: 12616: 12601: 12592: 12587: 12585: 12583: 12578: 12576: 12574: 12569: 12567: 12531: 12526: 12524: 12506: 12501: 12499: 12484: 12481: 12479: 12446: 12443: 12441: 12427: 12422: 12420: 12371:stellar system 12366: 12361: 12359: 12357: 12352: 12350: 12339: 12336:star catalogue 12334: 12332: 12287: 12282: 12280: 12240: 12234: 12225: 12216: 12214: 12212: 12207: 12205: 12171: 12166: 12164: 12162: 12159:speed of light 12157: 12138: 12136: 12131: 12129: 12120:Doppler effect 12100: 12095: 12093: 12082: 12077: 12075: 12035: 12030: 12028: 11983: 11978: 11976: 11972:ephemeris time 11924:diurnal motion 11919: 11914: 11912: 11861: 11856: 11854: 11843: 11838: 11836: 11811: 11806: 11803: 11798: 11796: 11769: 11764: 11762: 11733: 11728: 11725: 11720: 11718: 11716: 11711: 11709: 11707: 11702: 11700: 11683:solar granules 11673: 11668: 11666: 11620: 11615: 11613: 11547: 11542: 11540: 11538: 11532: 11530: 11493: 11488: 11486: 11484: 11479: 11477: 11449:diurnal motion 11444: 11439: 11437: 11415:orbital period 11410: 11405: 11403: 11364: 11359: 11357: 11346:vernal equinox 11313: 11308: 11306: 11273: 11268: 11266: 11263: 11258: 11256: 11247: 11244: 11242: 11225: 11222:secular motion 11220: 11218: 11215: 11212: 11210: 11172: 11167: 11165: 11163: 11160:scattered disc 11158: 11156: 11133: 11128: 11126: 11117: 11114: 11110: 11107: 11106: 11105: 11082: 11079: 11077: 11050: 11045: 11043: 11016: 11011: 11009: 10984:that orbits a 10955: 10950: 10948: 10929: 10924: 10922: 10909:, as with the 10871: 10866: 10864: 10845: 10840: 10822: 10795: 10790: 10788: 10784: 10779: 10777: 10775: 10770: 10768: 10725: 10720: 10718: 10716: 10711: 10709: 10689:for a typical 10681: 10676: 10674: 10655: 10650: 10648: 10641:radio antennas 10639:, using large 10621: 10616: 10614: 10597: 10592: 10588: 10585: 10584: 10583: 10580:emission lines 10556:of gas onto a 10528: 10523: 10504: 10471: 10466: 10464: 10446: 10443: 10439: 10436: 10435: 10434: 10419: 10414: 10412: 10397: 10394: 10392: 10385: 10380: 10378: 10376: 10371: 10369: 10342: 10337: 10335: 10332: 10327: 10325: 10302: 10299: 10297: 10261: 10256: 10254: 10228: 10223: 10221: 10219: 10214: 10212: 10185: 10180: 10178: 10153: 10148: 10146: 10131: 10126: 10124: 10087: 10082: 10080: 10074:planetary body 10065: 10059: 10057: 9984: 9979: 9977: 9947: 9942: 9940: 9917: 9912: 9910: 9907: 9902: 9900: 9862:secondary body 9848: 9845:planetary body 9843: 9841: 9832: 9829: 9827: 9785: 9780: 9778: 9769: 9766: 9764: 9748:ecliptic plane 9712: 9707: 9705: 9703: 9698: 9696: 9694: 9689: 9687: 9654: 9649: 9647: 9615: 9610: 9608: 9591: 9586: 9584: 9561: 9556: 9554: 9528: 9523: 9521: 9510: 9508:peak magnitude 9507: 9505: 9503: 9498: 9496: 9459: 9453: 9427: 9424: 9423: 9422: 9390: 9385: 9383: 9358: 9353: 9351: 9349: 9346: 9344: 9334:orbital period 9313: 9308: 9289: 9221: 9216: 9214: 9169:The imaginary 9167: 9162: 9160: 9124: 9121:orbital period 9119: 9117: 9101:ascending node 9072: 9067: 9065: 9063: 9058: 9056: 9035: 9030: 9000: 8991: 8986: 8984: 8969: 8964: 8962: 8934: 8931: 8929: 8924:center of mass 8885: 8880: 8878: 8874: 8869: 8867: 8858: 8853: 8851: 8844: 8839: 8837: 8797: 8792: 8790: 8763: 8758: 8756: 8729: 8724: 8722: 8720: 8715: 8713: 8659: 8654: 8652: 8641: 8636: 8634: 8619: 8616:OB association 8614: 8612: 8593: 8590: 8586: 8583: 8582: 8581: 8560: 8555: 8553: 8550: 8547:number density 8545: 8543: 8540: 8534: 8532: 8495: 8490: 8488: 8435: 8430: 8428: 8426: 8420: 8418: 8395: 8390: 8388: 8384: 8379: 8377: 8326: 8321: 8319: 8276: 8270: 8268: 8226: 8221: 8219: 8202: 8197: 8195: 8174: 8169: 8167: 8164:emission lines 8144: 8141: 8137: 8134: 8133: 8132: 8130: 8125: 8123: 8082: 8077: 8075: 8045: 8040: 8038: 8034:celestial body 8014: 8009: 8007: 7996: 7991: 7989: 7978: 7973: 7971: 7915: 7910: 7908: 7865: 7860: 7858: 7847: 7842: 7840: 7828: 7823: 7821: 7808: 7803: 7801: 7778:that orbits a 7770: 7765: 7763: 7730: 7725: 7723: 7712: 7707: 7674: 7671: 7620: 7615: 7613: 7592: 7589: 7587: 7583:micrometeorite 7572: 7569:micrometeoroid 7567: 7565: 7542: 7539:micrometeorite 7537: 7535: 7524: 7519: 7517: 7490: 7485: 7483: 7468: 7463: 7461: 7452: 7447: 7445: 7419:micrometeoroid 7395: 7390: 7388: 7363: 7360:Messier object 7358: 7356: 7329: 7326: 7324: 7309: 7304: 7302: 7291: 7288: 7286: 7270:orbital period 7264:circular orbit 7235: 7223: 7221: 7206:vernal equinox 7177: 7172: 7170: 7159: 7154: 7152: 7139:nuclear fusion 7115:A category of 7113: 7108: 7106: 7089: 7084: 7082: 7061: 7056: 7054: 7007: 7001: 6997: 6994: 6993: 6976: 6920: 6915: 6913: 6904: 6901: 6899: 6882:per second or 6854: 6849: 6847: 6831:ascending node 6814: 6808: 6806: 6804: 6799: 6797: 6770: 6767: 6765: 6750: 6747:limb darkening 6745: 6743: 6699:speed of light 6694: 6688: 6686: 6663: 6658: 6656: 6654: 6651:late-type star 6649: 6647: 6628: 6623: 6621: 6604: 6597: 6554:Lagrange point 6549: 6544: 6540: 6537: 6536: 6535: 6459: 6454: 6452: 6410: 6405: 6403: 6401: 6396: 6392: 6389: 6388: 6387: 6361: 6355: 6353: 6344: 6339: 6335: 6332: 6331: 6330: 6309: 6304: 6302: 6259: 6256:irregular moon 6254: 6252: 6250: 6245: 6243: 6241: 6236: 6234: 6196: 6191: 6189: 6174: 6169: 6167: 6140: 6134: 6132: 6130: 6124: 6122: 6117:detectable at 6103: 6098: 6096: 6056: 6051: 6049: 6038: 6033: 6031: 5978: 5973: 5969: 5966: 5965: 5964: 5929: 5926: 5924: 5903: 5900: 5898: 5873: 5870: 5868: 5839:Any imaginary 5837: 5832: 5830: 5775: 5770: 5768: 5755: 5750: 5748: 5718: 5713: 5711: 5636: 5631: 5629: 5602: 5597: 5595: 5593: 5588: 5586: 5571: 5566: 5564: 5547: 5544: 5542: 5505: 5500: 5496: 5493: 5492: 5491: 5450: 5445: 5424: 5411: 5406: 5404: 5402: 5397: 5395: 5362: 5357: 5355: 5334: 5329: 5327: 5299:orbital period 5288: 5282: 5280: 5266:same direction 5231: 5226: 5224: 5197: 5194: 5192: 5175: 5170: 5168: 5147: 5144: 5142: 5129: 5124: 5122: 5111: 5106: 5104: 5073: 5068: 5066: 5035: 5029: 5027: 5022:detectable at 5008: 5003: 5001: 4980:discovered by 4968: 4965:Galilean moons 4963: 4961: 4925: 4920: 4918: 4885: 4882:galaxy cluster 4880: 4878: 4844:center of mass 4809: 4804: 4802: 4759: 4756: 4754: 4729: 4724: 4722: 4670: 4665: 4663: 4617: 4612: 4610: 4608: 4603: 4601: 4599: 4594: 4592: 4577:constellations 4543: 4538: 4536: 4506: 4501: 4499: 4479: 4474: 4470: 4467: 4466: 4465: 4456: 4451: 4449: 4418: 4413: 4411: 4357: 4352: 4350: 4302: 4297: 4295: 4232: 4226: 4224: 4217: 4212: 4210: 4195: 4190: 4188: 4169: 4166: 4164: 4155: 4150: 4148: 4111: 4106: 4102: 4099: 4098: 4097: 4086: 4083: 4081: 4057: 4052: 4050: 4023: 4018: 4016: 3996: 3991: 3989: 3960: 3955: 3937: 3910: 3905: 3903: 3902:of any radius. 3894:center of mass 3886:kinetic energy 3881: 3876: 3874: 3862:directly above 3838:vernal equinox 3803: 3798: 3796: 3787: 3784: 3782: 3778:vernal equinox 3739: 3734: 3732: 3703: 3698: 3696: 3668: 3663: 3661: 3640: 3635: 3633: 3614: 3609: 3591: 3556:elliptic orbit 3551: 3546: 3544: 3519: 3514: 3512: 3501: 3496: 3494: 3472:vernal equinox 3433: 3428: 3385: 3324:ecliptic plane 3319: 3314: 3312: 3301: 3296: 3294: 3284: 3279: 3275: 3272: 3271: 3270: 3208: 3203: 3201: 3199: 3194: 3192: 3176: 3171: 3169: 3166:diurnal circle 3126: 3123:diurnal motion 3121: 3119: 3108: 3103: 3101: 3097:scattered disc 3039: 3034: 3032: 3027:ascending node 2994: 2989: 2987: 2956: 2951: 2949: 2898: 2892: 2890: 2871: 2868:decretion disk 2866: 2864: 2837: 2832: 2816:Circumstellar 2810: 2793:A ring-shaped 2791: 2786: 2782: 2779: 2778: 2777: 2749:appear to move 2693: 2688: 2686: 2652: 2649: 2647: 2645: 2642: 2640: 2627: 2622: 2620: 2607: 2602: 2600: 2577: 2572: 2570: 2559: 2553: 2551: 2530: 2525: 2523: 2521: 2516: 2514: 2483: 2477: 2475: 2473: 2468: 2466: 2447: 2442: 2440: 2413: 2408: 2406: 2381: 2376: 2374: 2363: 2358: 2356: 2319:compact object 2314: 2309: 2307: 2284: 2281: 2279: 2255: 2250: 2248: 2227: 2222: 2220: 2209: 2204: 2202: 2200: 2195: 2193: 2191: 2188: 2186: 2175: 2170: 2168: 2162: 2150:light, to the 2140:singly ionized 2129: 2120: 2103: 2100: 2098: 2096: 2091: 2089: 2068: 2062: 2060: 2005:with either a 1997: 1992: 1990: 1969: 1964: 1962: 1929: 1926:celestial pole 1924: 1922: 1911: 1906: 1904: 1863:The branch of 1861: 1856: 1814: 1779:The imaginary 1777: 1772: 1770: 1761:placed at the 1755: 1752: 1750: 1747: 1742: 1738: 1735: 1734: 1733: 1731: 1726: 1724: 1701:nuclear fusion 1691: 1686: 1684: 1656: 1653: 1651: 1649: 1644: 1642: 1633: 1628: 1626: 1595: 1590: 1588: 1573: 1568: 1566: 1559: 1554: 1552: 1511:center of mass 1507: 1502: 1476: 1473: 1472: 1471: 1456: 1451: 1449: 1447: 1442: 1440: 1426:orbital period 1400: 1395: 1393: 1324: 1319: 1317: 1313: 1308: 1306: 1267: 1262: 1260: 1258: 1253: 1251: 1236: 1231: 1229: 1214:semimajor axis 1204: 1198: 1196: 1166:constellations 1132: 1127: 1125: 1077: 1072: 1070: 1058: 1053: 1051: 1008:celestial body 1003: 998: 996: 981: 976: 974: 951: 946: 944: 931: 926: 924: 913: 908: 906: 887:on Earth, the 862: 857: 855: 806: 801: 799: 738: 733: 731: 710: 705: 703: 682: 679: 677: 627: 624:ascending node 622: 620: 597: 592: 590: 574:ascending node 550: 545: 543: 515:planetary body 504: 499: 497: 494: 489: 487: 471: 466: 464: 441: 436: 434: 417: 412: 410: 393: 388: 386: 365: 360: 358: 349: 346:albedo feature 344: 332:albedo feature 319: 286: 281: 279: 250: 244: 242: 221: 218:accretion disk 216: 214: 187: 182: 180: 159: 154: 150: 147: 144: 143: 141:External links 138: 133: 128: 47: 45: 42: 15: 9: 6: 4: 3: 2: 17097: 17086: 17083: 17081: 17078: 17076: 17073: 17072: 17070: 17055: 17052: 17050: 17047: 17045: 17042: 17040: 17037: 17035: 17032: 17030: 17027: 17025: 17022: 17020: 17017: 17015: 17012: 17010: 17007: 17005: 17002: 17000: 16997: 16995: 16992: 16990: 16987: 16985: 16982: 16980: 16977: 16975: 16972: 16970: 16967: 16963: 16960: 16958: 16955: 16953: 16950: 16948: 16945: 16943: 16940: 16939: 16937: 16933: 16930: 16928: 16925: 16924: 16922: 16920: 16917: 16915: 16912: 16910: 16907: 16903: 16900: 16898: 16895: 16894: 16892: 16890: 16887: 16885: 16882: 16880: 16877: 16875: 16872: 16870: 16867: 16865: 16862: 16860: 16857: 16855: 16852: 16850: 16847: 16845: 16842: 16840: 16837: 16835: 16832: 16830: 16827: 16825: 16822: 16820: 16817: 16815: 16812: 16810: 16807: 16805: 16802: 16800: 16797: 16796: 16793: 16789: 16785: 16777: 16772: 16770: 16765: 16763: 16758: 16757: 16754: 16741: 16732: 16729: 16720: 16719: 16716: 16709: 16705: 16700: 16696: 16693: 16689: 16686: 16682: 16681: 16679: 16675: 16670: 16666: 16663: 16659: 16656: 16652: 16649: 16645: 16644: 16642: 16638: 16635: 16631: 16628: 16624: 16621: 16617: 16614: 16610: 16607: 16603: 16598: 16594: 16593: 16591: 16590:Constellation 16587: 16584: 16580: 16577: 16573: 16570: 16569: 16564: 16561: 16557: 16554: 16550: 16547: 16543: 16540: 16536: 16533: 16529: 16526: 16522: 16519: 16515: 16514: 16512: 16508: 16501: 16497: 16494: 16490: 16487: 16483: 16480: 16476: 16473: 16469: 16466: 16462: 16459: 16455: 16452: 16448: 16445: 16441: 16438: 16434: 16431: 16427: 16426: 16424: 16422: 16416: 16405: 16401: 16396: 16392: 16391: 16389: 16385: 16382: 16378: 16375: 16371: 16368: 16364: 16361: 16357: 16354: 16350: 16347: 16343: 16340: 16336: 16333: 16329: 16326: 16322: 16319: 16315: 16312: 16308: 16307: 16305: 16303: 16299: 16292: 16288: 16285: 16281: 16278: 16274: 16271: 16267: 16264: 16260: 16257: 16253: 16250: 16246: 16245: 16243: 16241:Other methods 16239: 16232: 16228: 16223: 16219: 16218: 16216: 16212: 16209: 16205: 16202: 16195: 16190: 16185: 16181: 16178: 16177:Submillimetre 16174: 16171: 16167: 16166: 16164: 16160: 16151: 16147: 16146: 16144: 16140: 16137: 16136:Extragalactic 16133: 16129: 16128: 16126: 16122: 16115: 16111: 16108: 16104: 16101: 16100:Observational 16097: 16094: 16090: 16089: 16087: 16083: 16080: 16076: 16069: 16065: 16062: 16058: 16055: 16051: 16048: 16044: 16041: 16037: 16032: 16028: 16027: 16025: 16021: 16018: 16014: 16013: 16010: 16006: 15999: 15994: 15992: 15987: 15985: 15980: 15979: 15976: 15962: 15958: 15954: 15944: 15940: 15936: 15926: 15922: 15918: 15908: 15907: 15902: 15892: 15888: 15884: 15883: 15870: 15864: 15860: 15859: 15851: 15843: 15839: 15835: 15831: 15827: 15823: 15818: 15813: 15809: 15805: 15798: 15790: 15786: 15782: 15778: 15774: 15770: 15765: 15760: 15756: 15752: 15745: 15737: 15735:0-521-38996-8 15731: 15727: 15723: 15722: 15714: 15706: 15702: 15698: 15694: 15690: 15686: 15681: 15676: 15672: 15668: 15661: 15653: 15647: 15643: 15642: 15634: 15626: 15620: 15616: 15612: 15611: 15603: 15590:on 2011-10-24 15589: 15585: 15581: 15575: 15568: 15562: 15558: 15557: 15549: 15541: 15535: 15531: 15530: 15522: 15507: 15506: 15499: 15484: 15483: 15476: 15468: 15462: 15458: 15457: 15449: 15441: 15437: 15433: 15429: 15421: 15413: 15407: 15403: 15402: 15394: 15386: 15382: 15377: 15372: 15368: 15364: 15360: 15356: 15349: 15341: 15337: 15333: 15329: 15322: 15314: 15308: 15304: 15303: 15295: 15287: 15285:9780521529273 15281: 15277: 15276: 15268: 15261: 15255: 15251: 15247: 15240: 15232: 15225: 15217: 15213: 15209: 15202: 15194: 15190: 15186: 15182: 15178: 15174: 15170: 15166: 15159: 15144: 15140: 15133: 15118: 15114: 15107: 15100: 15094: 15090: 15089: 15081: 15073: 15069: 15065: 15061: 15054: 15047: 15043: 15039: 15037:9780199214938 15033: 15029: 15028: 15020: 15018: 15016: 15007: 15003: 14999: 14992: 14984: 14980: 14975: 14970: 14966: 14962: 14957: 14952: 14948: 14944: 14937: 14929: 14925: 14921: 14917: 14912: 14907: 14903: 14899: 14892: 14884: 14880: 14876: 14872: 14865: 14852:on 2022-02-23 14851: 14847: 14843: 14837: 14835: 14833: 14831: 14829: 14827: 14825: 14823: 14821: 14819: 14817: 14815: 14813: 14811: 14809: 14794: 14790: 14784: 14770: 14764: 14760: 14756: 14755: 14747: 14733: 14731:0-470-09220-3 14727: 14723: 14719: 14718: 14710: 14702: 14698: 14692: 14684: 14680: 14675: 14670: 14666: 14662: 14658: 14654: 14647: 14640: 14634: 14630: 14623: 14615: 14611: 14606: 14601: 14597: 14593: 14588: 14583: 14579: 14575: 14568: 14560: 14554: 14550: 14549: 14541: 14532: 14527: 14523: 14519: 14515: 14511: 14504: 14497: 14489: 14485: 14481: 14477: 14473: 14469: 14462: 14454: 14452:9780521339070 14448: 14444: 14443: 14435: 14427: 14421: 14417: 14413: 14412: 14404: 14397: 14391: 14387: 14386: 14378: 14376: 14374: 14372: 14367: 14357: 14354: 14352: 14349: 14347: 14344: 14342: 14339: 14337: 14334: 14333: 14324: 14321: 14314: 14310: 14304: 14298: 14292: 14286: 14280: 14274: 14271: 14264: 14260: 14256: 14250: 14244: 14240: 14233: 14227: 14224: 14219: 14210: 14209:binary system 14206: 14202: 14198: 14194: 14191: 14184: 14180: 14174: 14168: 14167: 14164: 14153: 14144: 14138: 14132: 14128: 14125: 14118: 14114: 14108: 14104: 14100: 14094: 14091: 14084: 14078: 14074: 14068: 14060: 14059: 14056: 14052: 14048: 14039: 14032: 14028: 14022: 14016: 14012: 14009: 14002: 13998: 13991: 13985: 13982: 13981:variable star 13977: 13968: 13962: 13958: 13955: 13949: 13945: 13941: 13940:physical laws 13937: 13933: 13929: 13923: 13917: 13911: 13907: 13903: 13900: 13894: 13893: 13890: 13886: 13878: 13873: 13865: 13862: 13855: 13849: 13843: 13836: 13833: 13826: 13820: 13819:emission line 13816: 13812: 13810:spiral galaxy 13806: 13800: 13796: 13793: 13786: 13780: 13774: 13768: 13764: 13758: 13752: 13736: 13730: 13727: 13726:tropical year 13721: 13718: 13711: 13705: 13699: 13693: 13689: 13683: 13677: 13673: 13670: 13664: 13658: 13655: 13649: 13645: 13637: 13636: 13628: 13623: 13620: 13613: 13605: 13599: 13593: 13587: 13581: 13575: 13569: 13563: 13557: 13556: 13553: 13540: 13533: 13527: 13521: 13513: 13507: 13501: 13495: 13487: 13481: 13475: 13469: 13463: 13459: 13457:tidal braking 13453: 13450: 13449:tidal locking 13444: 13441: 13434: 13428: 13422: 13416: 13415: 13412: 13404: 13403:tidal braking 13397: 13391: 13385: 13379: 13373: 13370: 13364: 13361: 13353: 13350: 13343: 13337: 13331: 13325: 13322: 13315: 13309: 13303: 13297: 13291: 13285: 13282: 13275: 13271: 13267: 13263: 13257: 13254:telluric star 13250: 13247: 13240: 13238:proper motion 13234: 13228: 13222: 13218: 13212: 13203: 13200: 13193: 13187: 13181: 13175: 13169: 13166: 13159: 13153: 13149: 13143: 13137: 13135:same location 13131: 13125: 13119: 13116: 13109: 13103: 13097: 13091: 13085: 13079: 13073: 13069: 13063: 13057: 13051: 13045: 13044: 13041: 13033: 13026: 13020: 13014: 13008: 13002: 12996: 12993: 12978: 12972: 12968: 12962: 12956: 12952: 12948: 12941: 12935: 12929: 12923: 12917: 12912:An extremely 12911: 12908: 12901: 12895: 12893:galactic core 12889: 12883: 12877: 12873: 12866: 12865: 12858: 12854: 12849: 12845: 12841: 12835: 12832: 12826: 12823: 12817: 12814: 12807: 12801: 12795: 12790:), including 12789: 12783: 12779: 12773: 12772: 12769: 12761: 12754: 12748: 12742: 12739: 12732: 12728: 12723:that studies 12722: 12716: 12713: 12707: 12704: 12698: 12695: 12688: 12686:coronal loops 12682: 12676: 12670: 12666: 12662: 12659: 12652: 12646: 12644:astrophysical 12640: 12639: 12636: 12635:stellar model 12624: 12621: 12614: 12608: 12602: 12599: 12593: 12590: 12584: 12581: 12575: 12572: 12565: 12559: 12554:. The modern 12553: 12547: 12541: 12540: 12537: 12529: 12522: 12516: 12515: 12512: 12504: 12497: 12491: 12485: 12477: 12473: 12469: 12465: 12459: 12453: 12447: 12439: 12434: 12428: 12425: 12418: 12412: 12406: 12400: 12394: 12392:star clusters 12388: 12382: 12376: 12375: 12372: 12364: 12358: 12355: 12349: 12348: 12345: 12342:Also spelled 12337: 12330: 12324: 12318: 12314: 12310: 12306: 12300: 12296: 12292: 12288: 12285: 12262: 12258: 12254: 12250: 12249: 12246: 12233: 12224: 12219: 12213: 12210: 12209:spiral galaxy 12203: 12197: 12193: 12187: 12181: 12180: 12177: 12169: 12163: 12160: 12152: 12151: 12149:spectroscopic 12142: 12137: 12134: 12127: 12121: 12117: 12113: 12107: 12101: 12098: 12091: 12090: 12083: 12080: 12073: 12066: 12061:, called the 12060: 12058:June solstice 12054: 12048: 12042: 12036: 12033: 12026: 12020: 12014: 12008: 12002: 11996: 11992: 11988: 11984: 11981: 11974: 11968: 11966:sidereal time 11962: 11956: 11950: 11944: 11938: 11932: 11926: 11920: 11917: 11910: 11904: 11898: 11892: 11886: 11884:dwarf planets 11880: 11874: 11868: 11862: 11859: 11852: 11851: 11844: 11841: 11834: 11828: 11827:optical depth 11825:at which the 11824: 11818: 11812: 11801: 11794: 11788: 11782: 11776: 11770: 11767: 11760: 11753: 11740: 11734: 11723: 11717: 11714: 11713:solar granule 11708: 11705: 11698: 11694: 11688: 11684: 11680: 11674: 11671: 11664: 11658: 11652: 11645: 11639: 11633: 11627: 11621: 11618: 11617:solar eclipse 11611: 11608: 11602: 11596: 11590: 11584: 11578: 11572: 11566: 11560: 11554: 11548: 11545: 11539: 11535: 11528: 11527: 11520: 11514: 11508: 11502: 11498: 11494: 11491: 11485: 11482: 11481:sidereal year 11475: 11469: 11463: 11457: 11451: 11445: 11442: 11441:sidereal time 11435: 11429: 11423: 11417: 11411: 11408: 11401: 11395: 11389: 11383: 11377: 11371: 11365: 11362: 11355: 11354: 11352:March equinox 11347: 11343: 11339: 11335: 11329: 11323: 11322: 11319: 11311: 11304: 11298: 11293: 11287: 11283: 11282: 11279: 11271: 11264: 11261: 11260:semi-diameter 11254: 11248: 11245:selenocentric 11240: 11234: 11230: 11226: 11223: 11216: 11208: 11202: 11198: 11194: 11188: 11182: 11181: 11178: 11170: 11169:scintillation 11164: 11161: 11154: 11148: 11144: 11140: 11134: 11131: 11124: 11118: 11115:Saber's beads 11112: 11103: 11099: 11095: 11089: 11083: 11075: 11069: 11063: 11057: 11051: 11048: 11041: 11040: 11038:optical depth 11033: 11027: 11021: 11017: 11014: 11007: 11001: 10995: 10989: 10983: 10977: 10976: 10973: 10969: 10968:orphan planet 10965: 10961: 10953: 10946: 10942: 10936: 10930: 10927: 10920: 10919: 10912: 10908: 10906:giant planets 10902: 10896: 10890: 10884: 10878: 10872: 10869: 10862: 10856: 10852: 10846: 10843: 10835: 10834: 10826: 10820: 10819: 10812: 10806: 10802: 10796: 10793: 10785: 10782: 10776: 10773: 10766: 10760: 10754: 10750: 10744: 10738: 10732: 10726: 10723: 10717: 10714: 10707: 10703: 10702:helium fusion 10698: 10694: 10688: 10682: 10679: 10672: 10666: 10662: 10656: 10653: 10646: 10642: 10638: 10634: 10629:that studies 10628: 10622: 10619: 10612: 10608: 10602: 10598: 10595: 10590: 10581: 10577: 10573: 10569: 10565: 10561: 10555: 10549: 10543: 10537: 10536: 10534: 10526: 10517: 10516: 10508: 10502: 10496: 10490: 10484: 10478: 10472: 10469: 10462: 10459: 10455: 10451: 10447: 10441: 10432: 10426: 10420: 10417: 10410: 10406: 10402: 10398: 10390: 10386: 10383: 10377: 10374: 10367: 10365:planetesimals 10361: 10355: 10349: 10343: 10340: 10333: 10330: 10329:proper motion 10323: 10322:line-of-sight 10319: 10313: 10307: 10303: 10295: 10294: 10287: 10281: 10277: 10271: 10270: 10267: 10266:direct motion 10259: 10252: 10246: 10245: 10242: 10238: 10234: 10226: 10220: 10217: 10210: 10206: 10202: 10198: 10192: 10186: 10183: 10176: 10170: 10164: 10160: 10154: 10151: 10144: 10138: 10132: 10129: 10122: 10116: 10110: 10104: 10098: 10094: 10088: 10085: 10079: 10078: 10075: 10071: 10062: 10055: 10049: 10047:planetesimals 10043: 10037: 10031: 10025: 10023:dwarf planets 10019: 10013: 10007: 10001: 9995: 9989: 9985: 9982: 9975: 9969: 9963: 9957: 9956: 9953: 9945: 9938: 9934: 9928: 9922: 9918: 9915: 9908: 9905: 9898: 9896:planetesimals 9892: 9886: 9880: 9874: 9868: 9864: 9858: 9857: 9854: 9846: 9839: 9833: 9825: 9821: 9819:planetesimals 9815: 9809: 9805: 9801: 9797: 9792: 9786: 9783: 9776: 9770: 9762: 9756: 9750: 9744: 9738: 9732: 9726: 9722: 9721: 9718: 9710: 9704: 9701: 9695: 9692: 9685: 9681: 9677: 9671: 9667: 9661: 9655: 9652: 9645: 9640: 9634: 9628: 9622: 9616: 9613: 9606: 9605: 9598: 9592: 9589: 9582: 9581: 9574: 9568: 9562: 9559: 9552: 9551: 9544: 9538: 9537: 9534: 9526: 9519: 9515: 9511: 9504: 9501: 9494: 9490: 9487:of the words 9486: 9482: 9476: 9470: 9466: 9460: 9456: 9448: 9442: 9441: 9433: 9429: 9420: 9414: 9410: 9404: 9400: 9399: 9396: 9388: 9381: 9377: 9375:perturbations 9371: 9365: 9359: 9356: 9350: 9342: 9336: 9330: 9324: 9318: 9314: 9311: 9310:orbital speed 9303: 9302: 9293: 9287: 9281: 9275: 9271: 9268: 9262: 9256: 9252: 9246: 9240: 9234: 9228: 9222: 9219: 9212: 9206: 9200: 9194: 9190: 9184: 9178: 9172: 9168: 9165: 9164:orbital plane 9158: 9152: 9146: 9140: 9134: 9133: 9130: 9122: 9115: 9109: 9103: 9097: 9091: 9085: 9079: 9073: 9070: 9064: 9061: 9054: 9048: 9046:orbital plane 9042: 9036: 9033: 9025: 9019: 9017:orbital plane 9013: 9012: 9004: 8998: 8992: 8989: 8982: 8976: 8970: 8967: 8960: 8956: 8950: 8944: 8943: 8940: 8926: 8920: 8914: 8908: 8902: 8896: 8890: 8886: 8883: 8875: 8872: 8865: 8859: 8856: 8849: 8845: 8842: 8835: 8829: 8825: 8819: 8813: 8811:planetesimals 8807: 8806: 8803: 8795: 8788: 8782: 8776: 8770: 8764: 8761: 8754: 8748: 8742: 8736: 8730: 8727: 8721: 8718: 8711: 8705: 8699: 8693: 8687: 8681: 8675: 8669: 8668: 8665: 8657: 8650: 8649: 8642: 8639: 8632: 8626: 8620: 8617: 8610: 8609:variable star 8606: 8602: 8598: 8595:A diagram of 8594: 8588: 8579: 8573: 8567: 8561: 8558: 8551: 8548: 8541: 8537: 8530: 8524: 8518: 8512: 8506: 8502: 8496: 8493: 8486: 8480: 8474: 8468: 8462: 8456: 8453:is below the 8452: 8446: 8442: 8436: 8433: 8427: 8423: 8416: 8410: 8406: 8402: 8396: 8393: 8385: 8382: 8375: 8369: 8367:star clusters 8363: 8357: 8356:ionized gases 8353: 8349: 8345: 8339: 8333: 8327: 8324: 8317: 8311: 8305: 8299: 8295: 8289: 8284:, such as an 8283: 8277: 8273: 8266: 8260: 8254: 8248: 8242: 8236: 8235: 8232: 8224: 8216: 8215: 8212: 8208: 8200: 8193: 8187: 8181: 8175: 8172: 8165: 8161: 8157: 8153: 8149: 8145: 8139: 8131: 8128: 8121: 8115: 8109: 8105: 8101: 8095: 8089: 8083: 8080: 8073: 8067: 8061: 8055: 8054: 8051: 8043: 8036: 8030: 8024: 8023: 8020: 8012: 8011:morning width 8006: 8005: 8002: 7994: 7987: 7986: 7979: 7976: 7969: 7968: 7961: 7960: 7953: 7947: 7941: 7935: 7929: 7928: 7925: 7921: 7913: 7906: 7902: 7896: 7890: 7884: 7882:tidal locking 7878: 7872: 7866: 7863: 7856: 7855: 7848: 7845: 7838: 7837: 7834: 7826: 7819: 7815: 7809: 7806: 7799: 7798: 7791: 7790: 7783: 7777: 7771: 7768: 7761: 7755: 7749: 7743: 7737: 7731: 7728: 7721: 7720: 7713: 7710: 7702: 7699: 7697:constellation 7693: 7692: 7685: 7678: 7672: 7669: 7663: 7656: 7650: 7644: 7638: 7632: 7627: 7625:barred spiral 7621: 7618: 7611: 7605: 7599: 7597:variable star 7593: 7590:microvariable 7585: 7579: 7574:A very small 7573: 7570: 7563: 7557: 7553: 7549: 7544:A very small 7543: 7540: 7533: 7529: 7525: 7522: 7515: 7509: 7503: 7497: 7491: 7488: 7487:meteor shower 7481: 7475: 7469: 7466: 7459: 7453: 7450: 7443: 7442:incandescence 7439: 7433: 7427: 7421: 7415: 7409: 7408: 7405: 7401: 7400:shooting star 7393: 7386: 7380: 7376: 7370: 7364: 7361: 7354: 7348: 7343:and of their 7342: 7336: 7330: 7322: 7316: 7310: 7307: 7300: 7299: 7292: 7284: 7278: 7272: 7266: 7260: 7254: 7248: 7242: 7236: 7231: 7226: 7219: 7218: 7211: 7207: 7203: 7199: 7193: 7187: 7186: 7183: 7175: 7174:March equinox 7168: 7167: 7160: 7157: 7150: 7144: 7140: 7136: 7132: 7126: 7120: 7114: 7111: 7110:main sequence 7104: 7100: 7094: 7090: 7087: 7080: 7074: 7068: 7062: 7059: 7058:magnetosphere 7052: 7050:rogue planets 7046: 7040: 7038:neutron stars 7034: 7028: 7022: 7018: 7014: 7008: 7004: 6999: 6989: 6988: 6980: 6974: 6968: 6962: 6958: 6954: 6948: 6942: 6940:synodic month 6936: 6930: 6929: 6926: 6918: 6911: 6905: 6897: 6891: 6885: 6881: 6877: 6873: 6867: 6861: 6855: 6852: 6845: 6839: 6833: 6827: 6821: 6815: 6811: 6805: 6802: 6795: 6789: 6783: 6777: 6771: 6764:of the image. 6763: 6762: 6757: 6751: 6748: 6741: 6735: 6729: 6707: 6701: 6695: 6691: 6684: 6683: 6678: 6674: 6670: 6664: 6661: 6655: 6652: 6646: 6645: 6642: 6638: 6634: 6626: 6619: 6613: 6607: 6600: 6592: 6588: 6584: 6579: 6573: 6567: 6566: 6563: 6559: 6555: 6547: 6542: 6533: 6529: 6527:dwarf planets 6523: 6521:asteroid belt 6517: 6511: 6505: 6500:in the outer 6499: 6493: 6487: 6481: 6475: 6469: 6468: 6465: 6457: 6450: 6448:perturbations 6444: 6442:orbital plane 6438: 6434: 6430: 6426: 6420: 6419: 6416: 6408: 6402: 6399: 6394: 6385: 6379: 6373: 6371:tropical year 6366: 6362: 6358: 6351: 6345: 6342: 6337: 6328: 6322: 6316: 6310: 6307: 6300: 6296: 6294:regular moons 6290: 6284: 6278: 6272: 6266: 6260: 6257: 6251: 6248: 6242: 6239: 6232: 6226: 6222: 6216: 6210: 6209: 6206: 6205:Laplace plane 6202: 6194: 6187: 6181: 6175: 6172: 6165: 6161: 6157: 6151: 6145: 6141: 6137: 6131: 6127: 6120: 6116: 6111:that studies 6110: 6104: 6101: 6094: 6090: 6084: 6080: 6075: 6071: 6065: 6061: 6057: 6054: 6047: 6046: 6039: 6036: 6029: 6023: 6019: 6015: 6009: 6005: 6001: 5997: 5993: 5989: 5985: 5979: 5976: 5971: 5962: 5958: 5952: 5946: 5942: 5936: 5930: 5922: 5916: 5910: 5904: 5896: 5892: 5886: 5882: 5878: 5874: 5866: 5860: 5854: 5848: 5842: 5838: 5835: 5828: 5822: 5816: 5810: 5806: 5800: 5794: 5788: 5782: 5776: 5773: 5766: 5760: 5756: 5753: 5746: 5744:galactic core 5740: 5734: 5728: 5727: 5724: 5716: 5709: 5703: 5697: 5695:main-sequence 5691: 5685: 5679: 5673: 5671:spectral type 5667: 5661: 5655: 5649: 5643: 5637: 5634: 5627: 5621: 5615: 5609: 5603: 5600: 5594: 5591: 5584: 5578: 5572: 5569: 5562: 5558: 5552: 5548: 5540: 5534: 5527: 5523: 5520: 5516: 5512: 5506: 5503: 5498: 5489: 5483: 5477: 5471: 5469:neutron stars 5465: 5461: 5457: 5451: 5448: 5441: 5440:Einstein ring 5437: 5436: 5428: 5422: 5418: 5412: 5409: 5403: 5400: 5393: 5391:open clusters 5387: 5381: 5379:galactic core 5375: 5369: 5363: 5360: 5353: 5347: 5341: 5335: 5332: 5325: 5319: 5313: 5307: 5301: 5295: 5289: 5285: 5278: 5272: 5268: 5262: 5256: 5251: 5245: 5244: 5241: 5237: 5229: 5222: 5216: 5210: 5204: 5198: 5190: 5186: 5182: 5176: 5173: 5166: 5160: 5154: 5148: 5140: 5136: 5130: 5127: 5120: 5116: 5112: 5109: 5102: 5096: 5092: 5088: 5084: 5080: 5074: 5071: 5064: 5062:neutron stars 5058: 5052: 5046: 5040: 5036: 5032: 5025: 5021: 5016:that studies 5015: 5009: 5006: 4999: 4995: 4991: 4987: 4983: 4979: 4975: 4969: 4966: 4959: 4957:superclusters 4953: 4947: 4941: 4935: 4934: 4931: 4923: 4916: 4914:superclusters 4910: 4908:galaxy groups 4904: 4902:star clusters 4898: 4892: 4886: 4883: 4876: 4870: 4864: 4858: 4852: 4846: 4840: 4834: 4828: 4822: 4816: 4810: 4807: 4800: 4794: 4788: 4784: 4778: 4772: 4766: 4760: 4752: 4746: 4740: 4736: 4730: 4727: 4726:galactic tide 4720: 4714: 4708: 4702: 4696: 4690: 4684: 4683: 4680: 4676: 4675:galactic year 4668: 4661: 4655: 4649: 4643: 4637: 4631: 4630: 4627: 4623: 4622:galactic core 4615: 4609: 4606: 4600: 4597: 4590: 4586: 4582: 4579: 4573: 4567: 4561: 4556: 4550: 4544: 4541: 4534: 4531: 4529:constellation 4525: 4519: 4513: 4507: 4504: 4497: 4491: 4486: 4480: 4477: 4472: 4463: 4457: 4454: 4447: 4441: 4437: 4433: 4429: 4425: 4423:variable star 4419: 4416: 4409: 4403: 4397: 4391: 4385: 4379: 4373: 4367: 4366: 4363: 4355: 4348: 4342: 4336: 4330: 4327: 4325:constellation 4321: 4315: 4309: 4303: 4300: 4293: 4287: 4281: 4275: 4269: 4266: 4264:constellation 4260: 4254: 4248: 4246:March equinox 4242: 4241: 4238: 4237:Cusp of Aries 4229: 4222: 4218: 4215: 4208: 4202: 4196: 4193: 4186: 4180: 4179:line of sight 4176: 4170: 4162: 4156: 4153: 4146: 4140: 4134: 4128: 4124: 4118: 4112: 4109: 4104: 4095: 4094: 4087: 4079: 4073: 4067: 4066: 4063: 4055: 4048: 4042: 4036: 4030: 4024: 4021: 4014: 4008: 4003: 3997: 3994: 3987: 3983: 3979: 3973: 3969: 3965: 3961: 3958: 3950: 3949: 3941: 3935: 3929: 3923: 3917: 3911: 3908: 3901: 3895: 3891: 3887: 3882: 3879: 3872: 3871: 3864: 3858: 3852: 3846: 3840: 3834: 3828: 3822: 3816: 3810: 3804: 3801: 3794: 3788: 3780: 3774: 3768: 3763:(forming the 3762: 3756: 3750: 3746: 3740: 3737: 3730: 3724: 3720: 3714: 3710: 3704: 3701: 3693: 3691:perturbations 3687: 3681: 3675: 3669: 3666: 3659: 3653: 3647: 3641: 3638: 3631: 3625: 3619: 3615: 3612: 3604: 3603: 3595: 3589: 3585: 3579: 3573: 3567: 3561: 3560: 3557: 3549: 3542: 3536: 3530: 3526: 3520: 3517: 3510: 3506: 3502: 3499: 3492: 3486: 3480: 3474: 3468: 3462: 3456: 3452: 3446: 3440: 3434: 3431: 3423: 3416: 3410: 3404: 3398: 3397: 3389: 3384:of the Earth. 3383: 3377: 3371: 3365: 3359: 3353: 3347: 3341: 3340:Earth's orbit 3337: 3333: 3332: 3329: 3325: 3317: 3310: 3309: 3302: 3299: 3291: 3285: 3282: 3277: 3268: 3262: 3256: 3250: 3244: 3240: 3236: 3233: 3227: 3221: 3219:main-sequence 3215: 3209: 3206: 3200: 3197: 3190: 3183: 3177: 3174: 3167: 3163: 3157: 3151: 3145: 3139: 3133: 3127: 3124: 3117: 3116: 3109: 3106: 3105:direct motion 3099: 3093: 3087: 3081: 3077: 3071: 3065: 3059: 3053: 3052: 3049: 3045: 3037: 3030: 3029: 3022: 3016: 3010: 3004: 3003: 3000: 2992: 2985: 2979: 2973: 2967: 2961: 2957: 2954: 2947: 2941: 2935: 2933:star clusters 2929: 2923: 2917: 2911: 2905: 2899: 2895: 2888: 2884: 2878: 2872: 2869: 2862: 2861: 2854: 2848: 2844: 2838: 2835: 2827: 2823: 2822: 2814: 2808: 2804: 2802:planetesimals 2798: 2792: 2789: 2784: 2775: 2771: 2767: 2761: 2757: 2751: 2745: 2739: 2737:constellation 2733: 2727: 2721: 2715: 2709: 2703: 2702: 2699: 2691: 2684: 2683: 2676: 2670: 2667:balances the 2666: 2662: 2661: 2658: 2646: 2638: 2632: 2628: 2625: 2618: 2614: 2608: 2605: 2598: 2592: 2586: 2582: 2578: 2575: 2569: 2568: 2565: 2556: 2549: 2543: 2540: 2539: 2536: 2528: 2522: 2519: 2512: 2506: 2500: 2494: 2488: 2484: 2480: 2474: 2471: 2464: 2462:solar eclipse 2458: 2452: 2448: 2445: 2438: 2437: 2430: 2424: 2420: 2414: 2411: 2410:constellation 2404: 2398: 2392: 2388: 2382: 2379: 2372: 2371: 2364: 2361: 2354: 2348: 2342: 2340:neutron stars 2336: 2330: 2324: 2323: 2320: 2312: 2305: 2301: 2295: 2293:proper motion 2289: 2285: 2277: 2273: 2269: 2266: 2262: 2256: 2253: 2246: 2242: 2238: 2234: 2228: 2225: 2218: 2215:bands of the 2214: 2210: 2207: 2201: 2198: 2192: 2185: 2184: 2181: 2178:Also spelled 2173: 2165: 2156: 2153: 2149: 2145: 2144:H and K lines 2141: 2137: 2132: 2123: 2114: 2108: 2104: 2097: 2094: 2087: 2081: 2075: 2069: 2065: 2058: 2056:giant planets 2052: 2046: 2040: 2034: 2028: 2022: 2020:outer planets 2016: 2010: 2004: 1998: 1995: 1988: 1982: 1976: 1970: 1967: 1960: 1954: 1948: 1942: 1936: 1930: 1927: 1920: 1919: 1912: 1909: 1902: 1896: 1890: 1884: 1878: 1872: 1868: 1862: 1859: 1851: 1845: 1839: 1833: 1832: 1825: 1818: 1812: 1806: 1800: 1794: 1788: 1782: 1778: 1775: 1768: 1764: 1760: 1756: 1748: 1745: 1740: 1732: 1729: 1722: 1718: 1712: 1710:main sequence 1706: 1702: 1698: 1692: 1689: 1682: 1678: 1674: 1673: 1670: 1666: 1665: 1650: 1647: 1640: 1638:event horizon 1634: 1631: 1624: 1620: 1614: 1608: 1602: 1596: 1593: 1586: 1580: 1574: 1571: 1564: 1560: 1557: 1550: 1544: 1538: 1532: 1528: 1522: 1518: 1512: 1508: 1505: 1497: 1491: 1490: 1482: 1478: 1469: 1465: 1461: 1457: 1454: 1448: 1445: 1438: 1432: 1428: 1422: 1420:orbital plane 1416: 1410: 1409: 1406: 1398: 1391: 1385: 1379: 1375: 1369: 1365: 1359: 1353: 1347: 1343: 1337: 1331: 1325: 1322: 1314: 1311: 1304: 1298: 1294: 1290: 1286: 1282: 1276: 1272: 1268: 1265: 1259: 1256: 1249: 1243: 1237: 1234: 1219: 1218:Earth's orbit 1215: 1211: 1205: 1201: 1194: 1188: 1184: 1180: 1174: 1168: 1163: 1157: 1151: 1145: 1139: 1133: 1130: 1123: 1117: 1111: 1105: 1099: 1093: 1087: 1086: 1083: 1075: 1068: 1067: 1064: 1061:Also spelled 1056: 1049: 1043: 1037: 1031: 1025: 1019: 1013: 1012: 1009: 1001: 994: 988: 982: 979: 972: 971: 964: 958: 956:binary system 952: 949: 941: 940: 937: 929: 922: 921: 914: 911: 910:astrodynamics 904: 903:biosignatures 900: 896: 890: 886: 882: 878: 872: 871: 868: 860: 853: 849: 845: 843:minor planets 839: 833: 827: 823: 819: 813: 807: 804: 803:asteroid belt 797: 791: 789:planetesimals 785: 779: 773: 767: 761: 757: 751: 746:of the inner 745: 739: 736: 729: 727:constellation 723: 717: 711: 708: 701: 695: 689: 683: 675: 674: 667: 661: 655: 649: 643: 637: 636: 633: 625: 618: 617: 610: 604: 598: 595: 588: 582: 576: 570: 564: 563: 560: 556: 548: 541: 535: 529: 523: 517: 511: 505: 502: 495: 492: 485: 481: 480: 477: 469: 462: 461: 454: 448: 442: 439: 432: 431: 424: 418: 415: 408: 407: 400: 394: 391: 384: 383: 376: 370: 366: 363: 356: 350: 347: 339: 335: 334: 327: 323: 317: 313: 307: 303: 297: 291: 287: 284: 277: 276:active galaxy 273: 267: 263: 257: 251: 247: 240: 234: 228: 222: 219: 212: 206: 200: 194: 188: 185: 178: 172: 170:main-sequence 166: 160: 157: 152: 142: 139: 137: 134: 132: 129: 127: 124: 121: 118: 115: 112: 109: 106: 103: 100: 97: 94: 91: 88: 85: 82: 79: 76: 73: 70: 67: 64: 61: 58: 55: 52: 49: 48: 40: 38: 34: 30: 26: 22: 16893:Engineering 16844:Cell biology 16823: 16814:Architecture 16566: 16546:Astrophysics 16525:Astrobiology 16189:Far-infrared 16143:Local system 16078:Astronomy by 16068:... in space 16060: 15965:, retrieved 15960: 15947:, retrieved 15942: 15929:, retrieved 15924: 15911:, retrieved 15905: 15895:, retrieved 15890: 15857: 15850: 15807: 15803: 15797: 15754: 15750: 15744: 15720: 15713: 15670: 15666: 15660: 15640: 15633: 15609: 15602: 15592:, retrieved 15588:the original 15583: 15574: 15555: 15548: 15528: 15521: 15510:, retrieved 15504: 15498: 15487:, retrieved 15481: 15475: 15455: 15448: 15431: 15427: 15420: 15400: 15393: 15358: 15354: 15348: 15331: 15327: 15321: 15301: 15294: 15274: 15267: 15245: 15239: 15230: 15224: 15207: 15201: 15168: 15164: 15158: 15147:, retrieved 15142: 15132: 15121:, retrieved 15116: 15106: 15087: 15080: 15063: 15059: 15053: 15026: 14997: 14991: 14946: 14942: 14936: 14901: 14897: 14891: 14874: 14870: 14864: 14854:, retrieved 14850:the original 14845: 14797:, retrieved 14795:, 2017-02-14 14792: 14783: 14772:, retrieved 14753: 14746: 14735:, retrieved 14716: 14709: 14696: 14691: 14656: 14652: 14646: 14628: 14622: 14577: 14573: 14567: 14547: 14540: 14513: 14509: 14496: 14471: 14467: 14461: 14441: 14434: 14410: 14403: 14384: 14201:neutron star 14195:A source of 14190:X-ray source 14162: 14159: 14054: 14050: 14046: 14043: 13947: 13888: 13884: 13881: 13841:astronomical 13778:mean anomaly 13735:true anomaly 13631: 13597:eccentricity 13576:), used for 13551: 13548: 13518:tilt erosion 13508:such as the 13496:A stream of 13492:tidal stream 13420:tidal forces 13410: 13407: 13173:conjunctions 13165:synodic time 13095:eccentricity 13083:sidereal day 13039: 13036: 12933:evolutionary 12860: 12822:supercluster 12793:brown dwarfs 12787:solar masses 12767: 12764: 12738:subsatellite 12634: 12633:Also simply 12631: 12535: 12532: 12510: 12507: 12370: 12367: 12354:star cluster 12344:star catalog 12343: 12340: 12251:The nominal 12244: 12241: 12231: 12222: 12182:A branch of 12175: 12172: 12146: 12133:spectroscopy 12085: 11858:Solar System 11846: 11800:solar radius 11670:solar facula 11606: 11588:sidereal day 11522: 11467:sidereal day 11421:Solar System 11361:sidereal day 11349: 11345: 11341: 11317: 11314: 11296:Kepler orbit 11277: 11274: 11176: 11173: 11073:sidereal day 11035: 10971: 10967: 10964:nomad planet 10963: 10959: 10956: 10952:rogue planet 10914: 10829: 10814: 10807:such as the 10755:about their 10752: 10722:regular moon 10652:radio source 10574:, and their 10532: 10529: 10511: 10458:longitudinal 10424:neutron star 10311:double stars 10289: 10282:such as the 10265: 10262: 10241:central body 10240: 10237:primary body 10236: 10232: 10229: 10200: 10142:dwarf planet 10136:minor planet 10108:debris disks 10084:planetesimal 10073: 10069: 10066: 10053:debris discs 9951: 9948: 9884:dwarf planet 9852: 9849: 9823: 9716: 9713: 9632:Kepler orbit 9612:perturbation 9600: 9576: 9546: 9532: 9529: 9492: 9488: 9436: 9403:nearly empty 9394: 9391: 9363:Kepler orbit 9297: 9266:dwarf planet 9254: 9238:eccentricity 9210:Solar System 9150:Solar System 9128: 9125: 9069:orbital node 9007: 8939:orbital plot 8938: 8935: 8855:open cluster 8833:Solar System 8801: 8798: 8679:Solar System 8673:observations 8663: 8660: 8644: 8600: 8596: 8400:compact star 8392:neutron star 8354:, and other 8258:minor planet 8230: 8227: 8210: 8206: 8203: 8049: 8046: 8042:moving group 8018: 8015: 8000: 7997: 7984:subsatellite 7981: 7966:subsatellite 7963: 7955: 7951:minor planet 7945:dwarf planet 7923: 7919: 7916: 7904: 7850: 7832: 7829: 7796:subsatellite 7793: 7785: 7781:minor planet 7727:minor planet 7715: 7687: 7664:, which the 7636:Solar System 7492:A series of 7404:falling star 7403: 7399: 7396: 7294: 7276:true anomaly 7267:in the same 7229: 7225:mean anomaly 7213: 7209: 7205: 7181: 7178: 7162: 7091:A numerical 7044:brown dwarfs 7021:galaxy halos 6983: 6960: 6956: 6924: 6921: 6759: 6680: 6640: 6636: 6632: 6629: 6602: 6595: 6561: 6557: 6553: 6550: 6530:, including 6503:Solar System 6463: 6460: 6414: 6411: 6407:Kepler orbit 6320:evolutionary 6298: 6273:, and often 6204: 6200: 6197: 6121:wavelengths. 6041: 6027:Solar System 5983:giant planet 5920:brown dwarfs 5841:great circle 5777:For a given 5722: 5719: 5625:Solar System 5568:heliocentric 5549:The precise 5515:O-type stars 5452:A branch of 5431: 5420: 5342:, including 5331:giant planet 5311:sidereal day 5239: 5235: 5232: 5100:Solar System 5078:giant planet 5026:wavelengths. 4929: 4926: 4922:galaxy group 4747:such as the 4712:Solar System 4678: 4674: 4671: 4625: 4621: 4618: 4571:solar masses 4383:Solar System 4361: 4358: 4236: 4233: 4184:star cluster 4152:field galaxy 4138:solar facula 4092:astrobiology 4089: 4077:Solar System 4061: 4058: 4034:Solar System 3944: 3866: 3856:September 22 3775:towards the 3620:between the 3598: 3565:Kepler orbit 3555: 3552: 3490:inclinations 3469:towards the 3444:Solar System 3392: 3363:Solar System 3327: 3323: 3320: 3304: 3298:eccentricity 3266:brown dwarfs 3254:white dwarfs 3196:dwarf planet 3178:Any pair of 3165: 3111: 3069:Solar System 3063:minor planet 3047: 3043: 3040: 3024: 3023:). Contrast 3020:Solar System 3008:orbital node 2998: 2995: 2971:neutron star 2915:Solar System 2856: 2820:debris disks 2817: 2773: 2769: 2759: 2697: 2694: 2678: 2656: 2653: 2596:Solar System 2563: 2560: 2534: 2531: 2470:coronal loop 2432: 2399:or the same 2366: 2334:white dwarfs 2318: 2315: 2311:compact star 2179: 2176: 2160: 2148:photospheric 2138:of a star's 2127: 2118: 2112:chromosphere 2109:in a star's 2093:chromosphere 1914: 1879:, including 1827: 1783:of a body's 1781:great circle 1759:spectrograph 1668: 1660: 1657: 1556:baryogenesis 1485: 1404: 1401: 1378:polar motion 1264:astrophysics 1209:Solar System 1149:Solar System 1109:star cluster 1081: 1078: 1062: 1059: 1007: 1004: 966: 935: 932: 928:astrogeology 916: 889:habitability 866: 863: 859:astrobiology 851: 847: 817:Solar System 749:Solar System 743:minor planet 669: 653:Solar System 641:orbital node 631: 628: 612: 608:Solar System 558: 554: 551: 475: 472: 456: 426: 402: 378: 374:A-type stars 329: 326:Syrtis Major 298:, such as a 275: 20: 18: 17014:Ornithology 16999:Meteorology 16984:Mathematics 16974:Ichthyology 16809:Archaeology 16804:Agriculture 16788:engineering 16613:Planetarium 16270:High-energy 16256:Cosmic rays 16208:Ultraviolet 15334:: 126–140, 15171:: 681–694, 15117:www.gnu.org 15066:: 503–511, 14904:, id. A29, 14474:: 763–777, 14299:across the 14090:white dwarf 13703:occultation 13610:topocentric 13603:inclination 13440:tidal force 13289:heliosphere 13067:fixed stars 13032:synodic day 12939:white dwarf 12881:black holes 12859:. Contrast 12612:binary star 12495:star system 12448:Any set of 12386:binary star 12363:star system 12307:due to the 12304:outer space 12105:binary star 11840:solar storm 11822:photosphere 11786:photosphere 11704:solar flare 11678:photosphere 11625:occultation 11582:fixed stars 11552:synodic day 11521:. See also 11506:outer space 11455:fixed stars 11427:fixed stars 11378:of its own 11375:fixed stars 11302:binary star 11067:synodic day 10934:tidal force 10926:Roche limit 10913:. See also 10868:ring system 10813:. Contrast 10810:fixed stars 10706:core region 10665:radio waves 10576:ultraviolet 10568:radio waves 10430:white dwarf 10339:protoplanet 10288:. Contrast 10285:fixed stars 10168:inclination 10150:polar orbit 10120:protoplanet 10011:star system 9986:Any set of 9952:planetology 9937:Ring Nebula 9887:, or other 9840:or planets. 9822:. The term 9802:by its own 9774:inclination 9736:inclination 9700:photosphere 9651:phase angle 9545:. Contrast 9518:light curve 9485:portmanteau 9474:light-years 9387:outer space 9250:inclination 9185:around its 8928:trajectory. 8760:occultation 8709:uncertainty 8591:O–C diagram 8447:, when the 8387:undetected. 8211:unaided eye 8158:. Most are 8119:cosmic rays 7954:. See also 7948:, or other 7936:orbiting a 7784:. See also 7738:around the 7701:Sagittarius 7680:The bright 7654:light-years 7561:cosmic dust 7521:metallicity 7337:across the 7093:logarithmic 7041:as well as 7032:black holes 7017:dark matter 6917:lunar phase 6868:, or other 6801:Local Group 6705:Julian year 6456:Kuiper belt 6357:Julian year 6035:inclination 5927:hypergalaxy 5881:Delta Scuti 5834:hour circle 5804:hour circle 5723:Hill radius 5715:Hill sphere 5707:white dwarf 5689:metallicity 5665:color index 5599:heliosphere 5545:heliocenter 5519:Ultraviolet 5507:An ionized 5502:H II region 5475:black holes 5180:phase angle 5044:light-years 4838:dark matter 4787:kiloparsecs 4782:light-years 4734:tidal force 4703:around the 4679:cosmic year 4581:Sagittarius 4420:A class of 4354:fixed stars 4192:first light 4122:photosphere 3986:attenuation 3785:equinoctial 3529:ellipsoidal 3342:around the 3235:giant stars 3188:binary star 3173:double star 2965:white dwarf 2834:declination 2788:debris disk 2690:culmination 2677:. See also 2547:outer space 2527:cosmic dust 2504:solar flare 2449:An aura of 2378:conjunction 2346:black holes 2206:color index 2026:Kuiper belt 1952:fixed stars 1763:Coudé focus 1688:brown dwarf 1618:double star 1600:star system 1592:binary star 1509:The common 1495:binary star 1293:temperature 881:abiogenesis 690:or Earth's 611:. Contrast 425:. Contrast 381:metallicity 316:cloud cover 210:light-years 156:A-type star 17069:Categories 17029:Psychiatry 16938:Geography 16909:Entomology 16606:Photometry 16583:Binoculars 16560:Astrometry 16421:telescopes 16318:Babylonian 16162:EM methods 16040:Astronomer 15967:2012-02-20 15949:2018-03-09 15939:"Glossary" 15931:2018-03-09 15913:2018-03-09 15897:2012-02-19 15868:038794138X 15594:2012-02-27 15539:0521780918 15512:2011-10-20 15489:2011-10-20 15259:0486646874 15149:19 January 15123:19 January 14956:1805.12143 14911:1609.02864 14856:2021-11-22 14799:2019-03-09 14774:2016-10-15 14759:OUP Oxford 14737:2012-02-29 14362:References 14205:black hole 14095:A type of 14040:(Virgo SC) 13966:multiverse 13938:, and the 13838:including 13804:luminosity 13687:luminosity 13395:halo stars 13321:terminator 13307:solar wind 13101:axial tilt 13052:(i.e. its 12848:geocentric 12563:luminosity 12468:Betelgeuse 12325:, and its 12322:luminosity 12277: ft/s 12201:astrometry 12102:A type of 11980:solar wind 11916:solar time 11722:solar mass 11692:solar limb 11501:atmosphere 11338:North Pole 11291:elliptical 11197:turbulence 11186:brightness 11093:star spots 11087:luminosity 11025:atmosphere 10891:such as a 10832:retrograde 10547:luminosity 10514:quadrature 10482:elongation 10468:quadrature 10409:periastron 10250:barycenter 10182:precession 10041:meteoroids 9990:bound non- 9919:A type of 9810:) and has 9787:A type of 9659:elongation 9588:perihelion 9533:pericenter 9401:The vast, 9328:barycenter 8932:orbit plot 8871:opposition 8848:convection 8794:Oort cloud 8740:telescopes 8664:arc length 8647:axial tilt 8601:calculated 8577:precession 8528:retrograde 8475:, and the 8397:A type of 8361:luminosity 8127:multiverse 8099:extrasolar 8084:A type of 8019:rise width 7920:minor moon 7709:minor axis 7603:luminosity 7473:atmosphere 7437:atmosphere 7258:pericenter 7202:North Pole 7156:major axis 7143:hydrogen-1 7124:luminosity 7066:solar wind 7009:A kind of 6925:Moon phase 6851:luminosity 6733:astrometry 6722:10 mi 6714:10 km 6690:light-year 6383:light-year 6282:retrograde 6238:ionosphere 6214:barycenter 6179:extinction 6091:, such as 6074:geocentric 5945:elliptical 5908:luminosity 5772:hour angle 5738:satellites 5641:luminosity 5638:A plot of 5590:heliopause 5484:, and the 5481:supernovae 5351:ice giants 5345:gas giants 5220:aberration 5214:light-time 5189:Lambertian 5126:geocentric 4850:elliptical 4647:luminosity 4453:Fulton gap 4445:red dwarfs 4415:flare star 4401:extrasolar 4337:meets the 4282:meets the 4167:field star 4144:solar limb 4129:. For the 4084:exobiology 3968:scattering 3964:absorption 3957:extinction 3933:luminosity 3611:elongation 3562:A type of 3521:A type of 3505:black body 3381:axial tilt 3239:Betelgeuse 3205:dwarf star 3134:(e.g. the 3088:, such as 2999:south node 2710:(e.g. the 2579:A type of 2574:cosmic ray 2535:space dust 2391:spacecraft 2268:proportion 2152:bolometric 2008:perihelion 1834:, and the 1804:axial tilt 1757:This is a 1705:hydrogen-1 1630:black hole 1612:barycenter 1504:barycenter 1488:barycenter 1460:true north 1417:plane and 1414:equatorial 1397:axial tilt 1329:precession 1310:atmosphere 1285:luminosity 1169:, and the 989:and other 978:astrometry 953:A type of 867:exobiology 783:planetoids 777:meteoroids 665:parameters 632:north node 484:atmosphere 405:perihelion 311:black body 304:, that is 261:luminosity 238:black hole 136:References 17080:Astronomy 16884:Economics 16849:Chemistry 16824:Astronomy 16678:Telescope 16284:Spherical 16231:Gamma-ray 16200:(optical) 16005:Astronomy 15705:118784209 15680:1101.2156 15385:120268049 15193:119578058 15046:18293428M 14983:119059288 14949:(2): 11, 14683:122679154 14287:) of the 14045:Also the 13944:constants 13883:Also the 13756:periapsis 13531:satellite 13525:obliquity 13511:Milky Way 13473:satellite 13377:Milky Way 13298:from the 13246:telescope 13141:night sky 13107:solar day 12985: m/s 12963:or other 12930:'s final 12921:transient 12907:supernova 12852:cosmology 12796:and some 12720:astronomy 12680:starspots 12671:inside a 12457:telescope 12444:starfield 12269: m/s 12111:telescope 12052:longitude 11991:electrons 11942:solar day 11896:asteroids 11789:into the 11609:solar day 11544:solar day 11525:night sky 11512:astronomy 11399:solar day 11177:twinkling 11152:Milky Way 10855:longitude 10704:in their 10643:known as 10626:astronomy 10553:accretion 10382:protostar 10347:planetary 10128:planetoid 10035:asteroids 10002:around a 9926:red giant 9830:planetary 9824:exoplanet 9525:periapsis 9469:arcsecond 9340:periapsis 9325:around a 8903:around a 8800:Also the 8685:asteroids 8638:obliquity 8445:nighttime 8432:night sky 8306:from the 8199:naked eye 8113:neutrinos 8102:origins: 8087:astronomy 7888:night sky 7642:night sky 7617:Milky Way 7609:magnitude 7577:meteoroid 7547:meteorite 7501:night sky 7479:meteorite 7465:meteoroid 7449:meteorite 7413:meteoroid 7252:periapsis 7180:Also the 7103:naked eye 7086:magnitude 6957:full moon 6781:periapsis 6660:libration 6641:Local SCI 6631:Also the 6512:from the 6485:asteroids 6437:hyperbola 6306:isochrone 6276:eccentric 6108:astronomy 6078:cosmology 6013:volatiles 5994:(such as 5975:ice giant 5961:Andromeda 5956:Milky Way 5887:. On the 5864:geocenter 5721:Also the 5701:red giant 5683:evolution 5462:known as 5460:spacetime 5385:satellite 5202:celestial 5158:geocenter 5108:geocenter 5070:gas giant 5056:hypernova 5050:supernova 5039:gamma ray 5024:gamma-ray 5013:astronomy 4984:in 1610: 4874:Milky Way 4862:irregular 4798:Milky Way 4750:Milky Way 4718:Milky Way 4691:within a 4585:Ophiuchus 4554:Milky Way 4484:Milky Way 4438:waves to 4377:night sky 4310:upon the 4249:upon the 4235:Also the 4200:telescope 4062:exoplanet 4001:Milky Way 3927:evolution 3832:longitude 3757:onto the 3637:ephemeris 3481:and many 3421:equinoxes 3263:known as 3251:known as 3161:night sky 3091:cubewanos 3060:class of 3057:dynamical 2997:Also the 2977:evolution 2962:, e.g. a 2927:night sky 2624:cosmology 2604:cosmogony 2581:radiation 2513:eruption. 2423:mythology 2263:are in a 2237:volatiles 2213:frequency 2044:asteroids 1866:astronomy 1721:deuterium 1405:obliquity 1389:night sky 1275:chemistry 1247:phenomena 1233:astronomy 1187:astrology 1178:equinoxes 1172:solstices 852:main belt 837:asteroids 721:night sky 630:Also the 580:periapsis 527:periapsis 429:periapsis 44:Contents 29:cosmology 25:astronomy 17054:Virology 17039:Robotics 17004:Mycology 16994:Medicine 16839:Calculus 16728:Category 16437:Category 16332:Egyptian 16249:Neutrino 16184:Infrared 16132:Galactic 16107:Sidewalk 16061:Glossary 16031:Timeline 15842:15648424 15789:17029463 15584:Galaxies 14614:14732824 14330:See also 14290:ecliptic 14133:and the 13961:causally 13915:galaxies 13899:universe 13832:twilight 13813:and its 13775:and the 13668:meridian 13561:asteroid 13432:prograde 13232:observer 13221:velocity 13072:sunrises 13009:with an 12915:luminous 12398:galaxies 12313:hydrogen 12291:spheroid 12116:spectrum 12032:solstice 11948:meridian 11893:such as 11807:☉ 11750:10 11729:☉ 11576:meridian 11473:meridian 10945:coalesce 10882:moonlets 10736:prograde 10713:redshift 10344:A large 9795:orbiting 9733:such as 9678:such as 9668:such as 9603:aphelion 9549:apoapsis 9489:parallax 9464:parallax 9439:parallax 9418:Universe 9226:orbiting 9198:ecliptic 9104:and the 9095:inclined 8633:O and B. 8597:observed 8557:nutation 8522:prograde 8505:coplanar 8503:that is 8463:such as 8405:neutrons 8381:neutrino 8373:galaxies 8348:hydrogen 8287:asteroid 8207:bare eye 8142:N galaxy 7975:moonmoon 7528:hydrogen 7431:asteroid 7340:meridian 7306:meridian 6961:new moon 6812:(☊ or Ω) 6790:) of an 6787:apoapsis 6784:and the 6727:galactic 6677:far side 6497:centaurs 6482:such as 6433:parabola 6424:orbiting 6380:and the 6270:inclined 6185:redshift 6160:hydrogen 6119:infrared 6004:nitrogen 5988:hydrogen 5858:meridian 5817:and the 5798:meridian 5561:spheroid 5487:Big Bang 5249:circular 5083:hydrogen 4998:Callisto 4994:Ganymede 4939:galaxies 4890:galaxies 4589:Scorpius 4046:galaxies 3982:observer 3980:and the 3869:solstice 3850:March 20 3841:and the 3568:with an 3316:ecliptic 3100:objects. 2945:galaxies 2930:such as 2887:Be stars 2847:latitude 2768:, and a 2743:meridian 2636:Universe 2612:universe 2435:asterism 2349:, or to 2265:rational 2142:calcium 2125:, where 1917:meridian 1843:ecliptic 1810:ecliptic 1570:Big Bang 1464:altitude 1373:nutation 1360:and the 1183:almanacs 1161:zodiacal 1041:asteroid 943:objects. 735:asteroid 707:asterism 568:orbiting 533:apoapsis 414:apoapsis 390:aphelion 131:See also 17019:Physics 16969:Geology 16879:Ecology 16829:Biology 16784:science 16740:Commons 16692:history 16662:Russian 16510:Related 16419:Optical 16404:Tibetan 16388:Serbian 16381:Persian 16325:Chinese 16302:Culture 16222:History 16093:Amateur 16024:History 16017:Outline 15822:Bibcode 15769:Bibcode 15685:Bibcode 15436:Bibcode 15363:Bibcode 15336:Bibcode 15212:Bibcode 15173:Bibcode 15068:Bibcode 15002:Bibcode 14961:Bibcode 14916:Bibcode 14879:Bibcode 14877:: 618, 14661:Bibcode 14592:Bibcode 14518:Bibcode 14476:Bibcode 13927:planets 13709:eclipse 13654:transit 13479:primary 13355:models. 13268:of the 13152:Jupiter 13138:in the 13092:due to 13061:primary 13006:primary 12857:Ptolemy 12839:planets 12768:substar 12746:natural 12615:system. 12551:spectra 12482:stellar 12410:planets 12299:gravity 12122:as the 11987:protons 11927:of the 11881:, five 11878:planets 11662:annular 11656:partial 11628:of the 11452:of the 11430:of the 11286:ellipse 11213:secular 11206:horizon 11031:opacity 10903:around 10847:In the 10800:primary 10758:primary 10753:in situ 10519:shadow. 10497:or the 10399:For an 10275:primary 10225:primary 10205:Mercury 10174:equator 10070:planemo 10017:planets 9993:stellar 9961:planets 9816:of all 9804:gravity 9800:rounded 9684:Jupiter 9635:of the 9626:orbital 9620:primary 9558:perigee 9542:primary 9372:if all 9369:primary 9285:secular 9274:Neptune 9188:primary 9026:(grey). 8954:primary 8850:occurs. 8841:opacity 8703:primary 8472:planets 8455:horizon 8312:at its 8191:horizon 8071:cluster 8028:azimuth 7912:moonlet 7788:moonlet 7686:of the 7495:meteors 7334:transit 7005:(MACHO) 6775:apsides 6736:is the 6562:L-point 6491:trojans 6429:ellipse 6299:in situ 6288:primary 6230:orbital 6203:or the 6083:Ptolemy 6060:Mercury 6024:in the 6022:Neptune 5943:(often 5801:to the 5752:horizon 5644:versus 5522:photons 5263:in the 5260:equator 5137:of the 5097:in the 5091:Jupiter 4978:Jupiter 4795:of the 4659:quasars 4551:of the 4514:of the 4461:planets 4374:in the 3943:Sample 3808:equator 3800:equinox 3792:equinox 3754:equator 3700:equator 3654:in the 3588:ellipse 3478:planets 3408:equator 3243:Antares 3231:evolved 3191:system. 3080:Neptune 2939:nebulae 2839:In the 2765:horizon 2633:of the 2615:or the 2585:protons 2276:Jupiter 1994:centaur 1894:natural 1888:planets 1871:motions 1792:equator 1563:baryons 1523:of the 1498:systems 1453:azimuth 1431:seasons 1386:in the 1289:density 1271:physics 1216:of the 1146:of the 1143:planets 826:Jupiter 814:in the 760:Jupiter 577:to its 571:body's 521:primary 506:In the 491:appulse 459:perigee 422:primary 362:Am star 204:parsecs 161:In the 16834:Botany 16708:Zodiac 16648:French 16353:Indian 16346:Hebrew 16085:Manner 15865: 15840: 15787: 15732: 15707:, A27. 15703: 15673:: 16, 15648: 15621: 15563: 15536: 15508:, NASA 15485:, NASA 15463: 15408: 15383: 15309: 15282: 15256: 15191: 15095: 15044: 15034: 14981: 14765: 14728: 14681: 14635: 14612: 14555: 14449: 14422: 14392: 14270:zodiac 14241:(ZAMS) 14223:zenith 14197:X-rays 14172:galaxy 13948:entire 13936:energy 13932:matter 13850:, and 13717:trojan 13600:, and 13573:planet 13505:galaxy 13335:planet 13199:syzygy 13185:aspect 13179:planet 12966:object 12899:galaxy 12874:(SMBH) 12844:Saturn 12782:fusion 12669:plasma 12438:merger 12432:galaxy 12416:comets 12317:helium 12295:plasma 12273:32.174 12024:comets 12012:aurora 12006:corona 11993:, and 11905:, and 11902:comets 11792:corona 11697:facula 11536:(SSSB) 11333:zenith 11231:, the 11138:galaxy 11098:RS CVn 11022:of an 10970:, and 10894:planet 10781:réseau 10572:X-rays 10544:. Its 10525:quasar 10416:pulsar 10359:planet 10092:planet 10050:, and 9970:, and 9932:planet 9878:planet 9872:planet 9837:planet 9782:planet 9757:, and 9745:. The 9579:apogee 9569:or an 9493:second 9455:parsec 9446:parsec 9322:orbits 9235:(e.g. 9191:. The 9179:of an 9080:of an 9014:. The 8900:planet 8894:object 8774:object 8691:comets 8599:minus 8352:helium 8323:nebula 8252:planet 8246:orbits 8185:zenith 8156:Quasar 8116:, and 7939:planet 7900:phases 7747:planet 7683:center 7630:galaxy 7532:helium 7457:meteor 7392:meteor 7374:comets 7346:zenith 7320:zenith 7246:period 7197:zenith 7072:planet 6972:waning 6966:waxing 6880:joules 6865:galaxy 6739:parsec 6571:bodies 6494:, and 6164:helium 6155:galaxy 6144:matter 6018:Uranus 6008:sulfur 6006:, and 6000:carbon 5996:oxygen 5992:helium 5953:. 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