17:
876:
907:
the inner and outer radii limits roughly correspond to the density limits for maser operation. At the inner boundary, the collisions between molecules are enough to remove a population inversion. At the outer boundary, the density and optical depth is low enough that the gain of the maser is diminished. The hydroxyl masers are supported chemical pumping. At the distances where these masers are found water molecules are disassociated by UV radiation.
592:
957:
936:, support the bulk of astrophysical masers. Various pumping schemes – both radiative and collisional and combinations thereof – result in the maser emission of multiple transitions of many species. For example, the OH molecule has been observed to mase at 1612, 1665, 1667, 1720, 4660, 4750, 4765, 6031, 6035, and 13441 MHz. Water and
664:
Small path differences across the irregularly shaped maser cloud become greatly distorted by exponential gain. Part of the cloud that has a slightly longer path length than the rest will appear much brighter (as it is the exponent of the path length that is relevant), and so maser spots are typically
400:
in the 1940s, and so the emission was at first attributed to a hypothetical form of interstellar matter named "mysterium", but the emission was soon identified as line emission from hydroxide molecules in compact sources within molecular clouds. More discoveries followed, with water emission in 1969,
906:
Both radiative and collisional pumping resulting from the shockwave have been suggested as the pumping mechanism for the silicon monoxide masers. These masers diminish for larger radii as the gaseous silicon monoxide condenses into dust, depleting the available maser molecules. For the water masers,
479:(FIR) emission has been used to conduct searches of the sky with optical telescopes (because optical telescopes are easier to use for searches of this kind), and likely objects are then checked in the radio spectrum. Particularly targeted are molecular clouds, OH-IR stars, and FIR active galaxies.
351:
The radiation from astrophysical masers can be quite weak and may escape detection due to the limited sensitivity, and relative remoteness, of astronomical observatories and due to the sometimes overwhelming spectral absorption from unpumped molecules of the maser species in the surrounding space.
1737:
McGuire, Brett A.; Loomis, Ryan A.; Charness, Cameron M.; Corby, Joanna F.; Blake, Geoffrey A.; Hollis, Jan M.; Lovas, Frank J.; Jewell, Philip R.; Remijan, Anthony J. (2012). "Interstellar
Carbodiimide (HNCNH): A New Astronomical Detection from the GBT PRIMOS Survey via Maser Emission Features".
1090:
Unlike terrestrial lasers and masers for which the excitation mechanism is known and engineered, the reverse is true for astrophysical masers. In general, astrophysical masers are discovered empirically then studied further in order to develop plausible suggestions about possible pumping schemes.
898:
support the pumping of different maser species at different distances from the star. Due to instabilities within the nuclear burning sections of the star, the star experiences periods of increased energy release. These pulses produce a shockwave that forces the atmosphere outward. Hydroxyl masers
1029:
and laboratory astrophysics due, in part, to the fact that they are valuable diagnostic tools for astrophysical environments which may otherwise elude rigorous quantitative study and because they may facilitate the study of conditions which are inaccessible in terrestrial laboratories. A global
1041:
is generally understood to mean the change in apparent brightness to the observer. Intensity variations can occur on timescales from days to years indicating limits on maser size and excitation scheme. However, masers change in various ways over various timescales.
1091:
Quantification of the transverse size, spatial and temporal variations, and polarisation state, typically requiring VLBI telemetry, are all useful in the development of a pump theory. Galactic formaldehyde masing is one such example that remains problematic.
714:. In a saturated maser, amplification of radiation depends linearly on the size of population inversion and the path length. Saturation of one transition in a maser can affect the degree of inversion in other transitions in the same maser, an effect known as
705:
The exponential growth in intensity of radiation passing through a maser cloud continues as long as pumping processes can maintain the population inversion against the growing losses by stimulated emission. While this is so the maser is said to be
1055:
variation of the observed frequency of the maser, permitting a three-dimensional mapping of the dynamics of the maser environment. Perhaps the most spectacular success of this technique is the dynamical determination of the distance to the galaxy
823:) embedded in a crusty silicate filler that orbit the Sun in eccentric orbits. As they approach the Sun, the volatiles vaporise to form a halo and later a tail around the nucleus. Once vaporised, these molecules can form inversions and mase.
858:
It is predicted that masers exist in the atmospheres of gas giant planets. Such masers would be highly variable due to planetary rotation (10-hour period for Jovian planets). Cyclotron masers have been detected at the north pole of
Jupiter.
1050:
Masers in star-forming regions are known to move across the sky along with the material that is flowing out from the forming star(s). Also, since the emission is a narrow spectral line, line-of-sight velocity can be determined from the
182:
This fundamental incongruency in language has resulted in the use of other paradoxical definitions in the field. For example, if the gain medium of a misaligned laser is emission-seeded but non-oscillating radiation, it is said to emit
834:
in 1994 resulted in maser emissions in the 22 GHz region from the water molecule. Despite the apparent rarity of these events, observation of the intense maser emission has been suggested as a detection scheme for
167:
Due to the differences between engineered and naturally occurring masers, it is often stated that astrophysical masers are not "true" masers because they lack oscillation cavities. However, the distinction between
1961:
Pogrebenko, S. V.; Gurvits, L. I.; Elitzur, M.; Cosmovici, C. B.; Avruch, I. M.; Montebugnoli, S.; Salerno, E.; Pluchino, S.; MacCaferri, G.; Mujunen, A.; Ritakari, J.; Wagner, J.; Molera, G.; Uunila, M. (2009).
1890:
396:: emission lines in space, of unknown origin, at a frequency of 1665 MHz. At this time many researchers still thought that molecules could not exist in space, even though they had been discovered by
343:
in laboratory lasers and masers may be achieved by selectively oscillating the desired modes, polarisation in natural masers will arise only in the presence of a polarisation-state–dependent pump or of a
431:
Another unexpected discovery was made in 1982 with the discovery of emission from an extra-galactic source with an unrivalled luminosity about 10 times larger than any previous source. This was termed a
1082:
and therefore their distance. This method is much more accurate than other distance determinations, and gives us information about the galactic distance scale, e.g. the distance of spiral arms.
697:, etc.) more than the edges or wings. This results in an emission line shape that is much taller but not much wider. This makes the line appear narrower relative to the unamplified line.
203:
to differentiate it from the laboratory phenomenon. This simply adds to the confusion, since both sources are superradiant. In some laboratory lasers, such as a single pass through a
335:
The simple existence of a pumped population inversion is not sufficient for the observation of a maser. For example, there must be velocity coherence along the line of sight so that
151:
engineered for terrestrial laboratory masers. The emission from an astrophysical maser is due to a single pass through the gain medium and therefore generally lacks the spatial
2262:
Herrnstein; Moran; Greenhill; Diamond; Inoue; Nakai; Miyoshi; Henkel; Riess (1999). "A 4% Geometric
Distance to the Galaxy NGC4258 from Orbital Motions in a Nuclear Gas Disk".
756:
of the maser gas but is nevertheless useful in describing maser emission. Masers have incredible effective temperatures, many around 10K, but some of up to 10K and even 10K.
867:
In 2009, S. V. Pogrebenko et al. reported the detection of water masers in the plumes of water associated with the
Saturnian moons Hyperion, Titan, Enceladus, and Atlas.
424:. First was hydroxide emission in 1968, then water emission in 1969 and silicon monoxide emission in 1974. Masers were discovered in external galaxies in 1973, and in the
1440:
Korotkov, A. N.; Averin, D. V.; Likharev, K. K. (1994). "TASERs: Possible dc pumped terahertz lasers using interwell transitions in semiconductor heterostructures".
2009:
Vlemmings; Diamond; van
Langevelde; M Torrelles (2006). "The Magnetic Field in the Star-forming Region Cepheus a from Water Maser Polarization Observations".
665:
much smaller than their parent clouds. The majority of the radiation will emerge along this line of greatest path length in a "beam"; this is termed
1717:
McGuire et al. (2012), "Interstellar
Carbodiimide (HNCNH) – A New Astronomical Detection from the GBT PRIMOS Survey via Maser Emission Features."
1030:
collaboration called the Maser
Monitoring Organisation, colloquially known as the M2O, are one prominent group of researchers in this discipline.
2315:
Brunthaler, A.; Reid, MJ; Falcke, H; Greenhill, LJ; Henkel, C (2005). "The
Geometric Distance and Proper Motion of the Triangulum Galaxy (M33)".
1098:
transitions of the OH molecule near 53 MHz are expected to occur but have yet to be observed, perhaps due to a lack of sensitive equipment.
991:
While some of the masers in star forming regions can achieve luminosities sufficient for detection from external galaxies (such as the nearby
1476:
2376:
Hoffman; Goss; Patrick Palmer; Richards (2003). "The
Formaldehyde Masers in NGC 7538 and G29.96–0.02: VLBA, MERLIN, and VLA Observations".
413:, as from their narrow line widths and high effective temperatures it became clear that these sources were amplifying microwave radiation.
363:
The study of masers provides valuable information on the conditions—temperature, density, magnetic field, and velocity—in environments of
199:: that is, the users wish the system to behave as a laser. The emission from astrophysical masers is, in fact, ASE but is sometimes termed
1850:
Cosmovici, C. B.; Montebugnoli, S.; Pogrebenko, S.; Colom, P. (1995). "Water MASER Detection at 22 GHZ after the SL-9/Jupiter
Collision".
736:
would have if producing the same emission brightness at the wavelength of the maser. That is, if an object had a temperature of about 10
1495:
Thum, C.; Strelnitski, V. S.; Martin-Pintado, J.; Matthews, H. E.; Smith, H. A. (1995). "Hydrogen recombination β-lines in MWC 349".
1060:
from the analysis of the motion of the masers in the black-hole disk. Also, water masers have been used to estimate the distance and
226:
are variously employed. For example, when lasers were initially developed in the visible portion of the spectrum, they were called
1094:
On the other hand, some masers have been predicted to occur theoretically but have yet to be observed in nature. For example, the
2089:
Fish; Reid; Argon; Xing-Wu Zheng (2005). "Full-Polarization Observations of OH Masers in Massive Star-Forming Regions: I. Data".
1327:
191:. This ASE is regarded as unwanted or parasitic. Some researchers would add to this definition the presence of insufficient
613:
1401:"An ISO survey of possible water and hydroxyl IRASER transitions towards the star-forming regions W49, W3(OH) and SGR B2M"
768:
of the emission. Astronomical masers are often very highly polarised, sometimes 100% (in the case of some OH masers) in a
2498:
960:
903:(AU), water masers at a distance of about 100 to 400 AU, and silicon monoxide masers at a distance of about 5 to 10 AU.
995:), masers observed from distant galaxies generally arise in wholly different conditions. Some galaxies possess central
740:
it would produce as much 1665-MHz radiation as a strong interstellar OH maser. Of course, at 10K the OH molecule would
1075:
639:
357:
621:
241:, since energy states of molecules generally provide the masing transition. Along these lines, some use the term
656:
of radiation passing through a maser cloud is exponential. This has consequences for the radiation it produces:
352:
This latter obstacle may be partially surmounted through the judicious use of the spatial filtering inherent in
617:
184:
1478:
Identifying Circumstellar Dust Around Oxygen-Rich Mira Variables With Maser Emission Via Continuum Elimination
681:-coherent path length, any variation of either will itself result in exponential change of the maser output.
1078:
observations of maser sources in late type stars and star forming regions provide determinations of their
1017:
with large luminosities. Hydroxyl, water, and formaldehyde masers are known to exist in these conditions.
16:
710:. However, after a point, the population inversion cannot be maintained any longer and the maser becomes
442:
339:
does not prevent inverted states in different parts of the gain medium from radiatively coupling. While
2067:
1947:
2164:
846:
that can mase. In 1997, 1667-MHz maser emission characteristic of hydroxide was observed from comet
2493:
602:
57:
28:
1383:
179:
lasers was intentionally disregarded by the laser community in the early years of the technology.
2503:
2142:
Wardle, M.; Yusef-Zadeh, F (2002). "Supernova Remnant OH Masers: Signposts of Cosmic Collision".
1562:
785:
606:
487:
The following species have been observed in stimulated emission from astronomical environments:
2159:
1079:
827:
728:
372:
316:
254:
33:
921:
769:
250:
200:
138:
2216:
2032:
1979:
1578:
1508:
1279:
875:
2452:
2395:
2334:
2281:
2224:
2212:
2151:
2108:
2071:
2028:
1975:
1902:
1876:
1859:
1814:
1757:
1656:
1574:
1535:
1504:
1449:
1412:
1356:
1275:
765:
340:
204:
141:
8:
1313:
1107:
773:
694:
690:
510:
496:
289:
152:
111:
46:
2456:
2399:
2338:
2285:
2155:
2112:
2075:
1963:
1906:
1863:
1818:
1761:
1660:
1539:
1453:
1416:
1360:
1135:
Davis R.D., Rowson B., Booth R.S., Cooper A.J., Gent H., Adgie R.L., Crowther J.H. 1967
441:
A weak disk maser was discovered in 1995 emanating from the star MWC 349A, using NASA's
211:
stage, the physics is directly analogous to an amplified ray in an astrophysical maser.
2470:
2442:
2411:
2385:
2358:
2324:
2297:
2271:
2185:
2124:
2098:
2044:
2018:
1991:
1832:
1804:
1773:
1747:
1646:
1609:
1317:
1291:
976:
836:
572:
327:
and 300 GHz; that is, wavelengths between 30 cm and 1 mm, respectively.
80:
76:
2431:"A search for 53 MHz OH line near G48.4$ –$ 1.4 using the National MST Radar Facility"
1769:
1523:
2465:
2430:
2415:
2350:
2301:
2177:
2128:
1995:
1836:
1680:
1590:
1425:
1400:
1323:
1295:
1069:
992:
968:
900:
208:
130:
2474:
2362:
2189:
2048:
1777:
2460:
2403:
2342:
2289:
2220:
2169:
2116:
2036:
1983:
1929:
1822:
1765:
1672:
1668:
1664:
1631:
1582:
1543:
1457:
1420:
1364:
1283:
1146:
Cheung A.C., Rank D.M., Townes C.H., Thornton D.D., Welch W.J., Crowther J.H. 1969
1008:
980:
559:
553:
406:
196:
148:
1987:
1877:
Radio Search for Extrasolar Cometary Impacts at 22 GHz (water Maser Emission)
438:
because of its great luminosity; many more megamasers have since been discovered.
2040:
1699:
1586:
1095:
1026:
929:
677:
As the gain of a maser depends exponentially on the population inversion and the
397:
61:
409:
emission in 1974, all emanating from within molecular clouds. These were termed
1827:
1793:"First Detection of CS Masers around a High-mass Young Stellar Object, W51 e2e"
1792:
1547:
975:
The 1720 MHz maser transition of hydroxide is known to be associated with
916:
895:
417:
353:
345:
258:
230:
1920:
Ogley, Richard; Richards, Anita; Spencer, Ralph (1997). "A masing Hale-Bopp".
1287:
1110: – Matter and radiation in the space between the star systems in a galaxy
940:
masers are also typical of these environments. Relatively rare masers such as
2487:
1933:
1594:
1369:
1344:
1061:
1052:
1004:
880:
777:
749:
368:
364:
336:
134:
49:
2346:
2173:
1522:
Snyder, Lewis E.; Buhl, David; Zuckerman, B.; Palmer, Patrick (1969-03-31).
1266:
Strelnitski, Vladimir (1997). "Masers, Lasers and the Interstellar Medium".
2354:
2181:
1684:
1610:"Darkness Amplification by Stimulated Absorption of Radiation, No Kidding!"
945:
501:
476:
457:
425:
245:
to describe any system that exploits an electronic transition and the term
2447:
2390:
2329:
2276:
2103:
2023:
2008:
1386:
1065:
933:
925:
781:
753:
745:
172:
156:
842:
Ultraviolet light from the Sun breaks down some water molecules to form
1676:
1309:
996:
741:
733:
421:
376:
293:
270:
266:
122:
72:
1494:
1461:
1013:
883:
847:
843:
792:
491:
434:
301:
145:
119:
53:
1849:
591:
2407:
2238:
2120:
1809:
1190:
Knowles S.H., Mayer C.H., Cheung A.E., Rank D.M., Townes C.H. 1969
1057:
937:
678:
531:
402:
192:
2293:
1752:
1725:
1651:
2375:
1960:
941:
831:
820:
816:
811:
are small bodies (5 to 15 km diameter) of frozen volatiles (
566:
519:
310:
24:
752:
energy), so the brightness temperature is not indicative of the
133:
energy levels of the species in the gain medium which have been
2428:
2261:
1000:
964:
737:
274:
126:
69:
20:
689:
Exponential gain also amplifies the centre of the line shape (
2314:
887:
808:
453:
107:
103:
92:
65:
456:) sub-thermal population in the 4830 MHz transition of
1322:. Vol. 83. National Academy of Sciences. p. 202.
1003:
in size) is falling. Excitations of these molecules in the
2088:
1736:
1025:
Astronomical masers remain an active field of research in
1852:
AAS/Division for Planetary Sciences Meeting Abstracts #27
1521:
1168:
Ball J.A., Gottlieb C.A., Lilley A.E., Radford H.E. 1970
956:
379:, leading to refinements in existing theoretical models.
324:
1889:
Ogley, Richard; Richards, Anita; Spencer, Ralph (1997).
1124:
Weaver H., Dieter N.H., Williams D.R.W., Lum W.T. 1965
1439:
1316:(2003). "Arthur Schawlow". In Edward P. Lazear (ed.).
776:. This polarisation is due to some combination of the
581:
257:
transition, regardless of the output frequency. Some
1919:
1888:
1201:
Buhl D., Snyder L.E., Lovas F.J., Johnson D.R. 1974
214:
Furthermore, the practical limits of the use of the
1302:
999:into which a disk of molecular material (about 0.5
392:In 1965 an unexpected discovery was made by Weaver
288:has been used to describe laboratory masers in the
1632:"Coherent Perfect Absorbers: Time-Reversed Lasers"
1524:"Microwave Detection of Interstellar Formaldehyde"
416:Masers were then discovered around highly evolved
2435:Monthly Notices of the Royal Astronomical Society
2141:
1405:Monthly Notices of the Royal Astronomical Society
2485:
1629:
780:, magnetic beaming of the maser radiation, and
319:community typically limits the use of the word
144:. However, naturally occurring masers lack the
1342:
2203:Lo, K.Y. (2005). "Mega-Masers and Galaxies".
1790:
899:occur at a distance of about 1,000 to 10,000
482:
97:
2429:Menon; Anish Roshi; Rajendra Prasad (2005).
2205:Annual Review of Astronomy and Astrophysics
2091:The Astrophysical Journal Supplement Series
1567:Annual Review of Astronomy and Astrophysics
1265:
1223:Baan W.A., Wood P.A.D., Haschick A.D. 1982
948:may also be found in star-forming regions.
620:. Unsourced material may be challenged and
330:
1484:(Thesis). University of Missouri-Columbia.
1045:
2464:
2446:
2389:
2328:
2275:
2163:
2102:
2022:
1826:
1808:
1751:
1697:
1650:
1424:
1398:
1368:
1308:
640:Learn how and when to remove this message
159:purity expected from a laboratory maser.
986:
955:
874:
853:
387:
15:
1791:Ginsburg, Adam; Goddi, Ciriaco (2019).
1630:Chong; Ge; Cao; Stone (July 30, 2010).
1474:
1343:Schawlow, A. L.; Townes, C. H. (1958).
910:
475:The connections of maser activity with
2486:
2225:10.1146/annurev.astro.41.011802.094927
1964:"Water masers in the Saturnian system"
1879:, Catastrophic Events Conference, 2000
1560:
870:
764:An important aspect of maser study is
323:to frequencies between roughly 1
315:in reference to the gain species. The
1607:
1561:Townes, Charles H. (September 1997).
951:
894:The conditions in the atmospheres of
798:
249:to describe a system that exploits a
2061:
1608:Volpe, Giorgio (November 10, 2010).
862:
672:
618:adding citations to reliable sources
585:
1020:
464:CO) was observed in 1969 by Palmer
45:is a naturally occurring source of
13:
2202:
1399:Gray, M. D.; Yates, J. A. (1999).
721:
582:Characteristics of maser radiation
265:to describe a maser emitting at a
79:, or various other conditions in
14:
2515:
1719:The Astrophysical Journal Letters
1212:Whiteoak J.B., Gardner F.F. 1973
684:
358:very long baseline interferometry
2466:10.1111/j.1365-2966.2004.08517.x
1698:Lachowicz, Paweł (16 May 2007),
1426:10.1046/j.1365-8711.1999.03010.x
732:of a maser is the temperature a
590:
277:community terms similar sources
118:) and monochromatic, having the
2422:
2369:
2308:
2255:
2231:
2196:
2135:
2082:
2055:
2002:
1954:
1940:
1913:
1882:
1870:
1843:
1784:
1730:
1726:https://arxiv.org/abs/1209.1590
1711:
1691:
1623:
1601:
1554:
1241:
1230:
1219:
1179:Wilson W.J., Darrett A.H. 1968
791:Many of the characteristics of
759:
162:
1669:10.1103/PhysRevLett.105.053901
1515:
1488:
1468:
1433:
1392:
1377:
1336:
1268:Astrophysics and Space Science
1259:
1245:Elitzur M. Annu. Rev. Astron.
1208:
1197:
1186:
1175:
1164:
1153:
1142:
1131:
1120:
1085:
1033:
886:, showing dust production and
784:pumping which favours certain
772:, and to a lesser degree in a
185:amplified spontaneous emission
1:
2064:Maser Sources in Astrophysics
1563:"A Physicist Court Astronomy"
1345:"Infrared and Optical Masers"
1253:
700:
86:
60:. This emission may arise in
1968:Astronomy & Astrophysics
1639:Yale Physical Review Letters
1587:10.1146/annurev.astro.35.1.0
470:
382:
7:
1988:10.1051/0004-6361:200811186
1770:10.1088/2041-8205/758/2/L33
1475:Shepard, Lisa (July 2021).
1101:
443:Kuiper Airborne Observatory
52:emission, typically in the
10:
2520:
2499:Astronomical radio sources
2068:Cambridge University Press
2041:10.1051/0004-6361:20054275
2011:Astronomy and Astrophysics
1922:Astronomy & Geophysics
1895:Irish Astronomical Journal
1617:Optics and Photonics Focus
1548:10.1103/PhysRevLett.22.679
1497:Astronomy and Astrophysics
1157:Snyder L.E., Buhl D. 1974
914:
659:
483:Known interstellar species
98:Discrete transition energy
90:
2378:The Astrophysical Journal
1740:The Astrophysical Journal
815:, water, carbon dioxide,
803:
1828:10.3847/1538-3881/ab4790
1797:The Astronomical Journal
1370:10.1103/PhysRev.112.1940
1114:
1068:, including that of the
795:emission are different.
331:Astrophysical conditions
58:electromagnetic spectrum
2347:10.1126/science.1108342
2217:2005ARA&A..43..625L
2174:10.1126/science.1068168
2033:2006A&A...448..597V
1980:2009A&A...494L...1P
1579:1997ARA&A..35D..13T
1528:Physical Review Letters
1509:1995A&A...300..843T
1442:Applied Physics Letters
1288:10.1023/A:1000892300429
1280:1997Ap&SS.252..279S
1046:Distance determinations
356:techniques, especially
142:population distribution
129:difference between two
2062:Gray, Malcolm (2012).
1934:10.1093/astrog/38.4.22
1080:trigonometric parallax
972:
934:giant molecular clouds
891:
729:brightness temperature
405:emission in 1970, and
317:electrical engineering
106:, the emission from a
38:
987:Extragalactic sources
959:
922:Young stellar objects
878:
854:Planetary atmospheres
652:The amplification or
388:Historical background
348:in the gain medium.
304:generally call these
298:sub-millimeter masers
201:superradiant emission
23:on the north pole of
19:
1891:"A Masing Hale-Bopp"
1701:Astrophysical masers
1319:Biographical Memoirs
911:Star-forming regions
826:The impact of comet
748:is greater than the
614:improve this section
2457:2005MNRAS.356..958M
2400:2003ApJ...598.1061H
2339:2005Sci...307.1440B
2286:1999Natur.400..539H
2156:2002Sci...296.2350W
2113:2005ApJS..160..220F
2076:2012msa..book.....G
2070:. pp. 218–30.
1907:1997IrAJ...24...95G
1864:1995DPS....27.2802C
1819:2019AJ....158..208G
1762:2012ApJ...758L..33M
1661:2010PhRvL.105e3901C
1540:1969PhRvL..22..679S
1454:1994ApPhL..65.1865K
1417:1999MNRAS.310.1153G
1361:1958PhRv..112.1940S
1108:Interstellar medium
1064:of galaxies in the
979:that interact with
971:with maser emission
924:and (ultra)compact
871:Stellar atmospheres
754:kinetic temperature
373:centres of galaxies
233:advocated that the
77:stellar atmospheres
43:astrophysical maser
977:supernova remnants
973:
952:Supernova remnants
901:astronomical units
892:
879:Pulsations of the
837:extrasolar planets
799:Maser environments
273:, even though the
131:quantum-mechanical
81:interstellar space
39:
2323:(5714): 1440–43.
2150:(5577): 2350–54.
1948:"3and12mm_masers"
1448:(15): 1865–1867.
1329:978-0-309-08699-8
1070:Triangulum Galaxy
1039:Maser variability
993:Magellanic Clouds
969:supernova remnant
863:Planetary systems
673:Rapid variability
650:
649:
642:
296:might call these
292:regime, although
2511:
2479:
2478:
2468:
2450:
2448:astro-ph/0501649
2426:
2420:
2419:
2393:
2391:astro-ph/0308256
2373:
2367:
2366:
2332:
2330:astro-ph/0503058
2312:
2306:
2305:
2279:
2277:astro-ph/9907013
2270:(6744): 539–41.
2259:
2253:
2252:
2250:
2249:
2235:
2229:
2228:
2200:
2194:
2193:
2167:
2139:
2133:
2132:
2106:
2104:astro-ph/0505148
2086:
2080:
2079:
2059:
2053:
2052:
2026:
2024:astro-ph/0510452
2006:
2000:
1999:
1958:
1952:
1951:
1944:
1938:
1937:
1917:
1911:
1910:
1886:
1880:
1874:
1868:
1867:
1847:
1841:
1840:
1830:
1812:
1788:
1782:
1781:
1755:
1734:
1728:
1715:
1709:
1708:
1706:
1695:
1689:
1688:
1654:
1636:
1627:
1621:
1620:
1614:
1605:
1599:
1598:
1573:(1): xiii–xliv.
1558:
1552:
1551:
1519:
1513:
1512:
1492:
1486:
1485:
1483:
1472:
1466:
1465:
1462:10.1063/1.112865
1437:
1431:
1430:
1428:
1396:
1390:
1381:
1375:
1374:
1372:
1355:(6): 1940–1949.
1340:
1334:
1333:
1306:
1300:
1299:
1263:
1249:. 1992 30 75–112
1244:
1234:Cohen R.J. Rep.
1233:
1222:
1214:Astrophys. Lett.
1211:
1200:
1189:
1178:
1167:
1156:
1145:
1134:
1123:
1021:Ongoing research
981:molecular clouds
930:molecular clouds
828:Shoemaker-Levy 9
770:circular fashion
716:competitive gain
645:
638:
634:
631:
625:
594:
586:
448:Evidence for an
428:in comet halos.
407:silicon monoxide
337:Doppler shifting
308:or specifically
197:lasing threshold
170:oscillator-based
62:molecular clouds
37:
29:cyclotron masers
2519:
2518:
2514:
2513:
2512:
2510:
2509:
2508:
2494:Radio astronomy
2484:
2483:
2482:
2427:
2423:
2374:
2370:
2313:
2309:
2260:
2256:
2247:
2245:
2237:
2236:
2232:
2201:
2197:
2165:10.1.1.524.2946
2140:
2136:
2087:
2083:
2060:
2056:
2007:
2003:
1959:
1955:
1950:. 20 July 2022.
1946:
1945:
1941:
1918:
1914:
1887:
1883:
1875:
1871:
1848:
1844:
1789:
1785:
1735:
1731:
1724:(2): L33 arXiv:
1716:
1712:
1704:
1696:
1692:
1634:
1628:
1624:
1612:
1606:
1602:
1559:
1555:
1534:(13): 679–681.
1520:
1516:
1493:
1489:
1481:
1473:
1469:
1438:
1434:
1397:
1393:
1382:
1378:
1349:Physical Review
1341:
1337:
1330:
1314:Townes, Charles
1307:
1303:
1264:
1260:
1256:
1238:1989 52 881–943
1117:
1104:
1096:magnetic dipole
1088:
1048:
1036:
1027:radio astronomy
1023:
989:
954:
919:
913:
896:late-type stars
873:
865:
856:
806:
801:
762:
724:
722:High brightness
703:
687:
675:
662:
646:
635:
629:
626:
611:
595:
584:
578:
549:
535:
528:
523:
514:
505:
485:
473:
463:
418:late-type stars
390:
385:
354:interferometric
333:
300:and laboratory
259:astrophysicists
228:optical masers.
165:
100:
95:
89:
56:portion of the
31:
12:
11:
5:
2517:
2507:
2506:
2504:Astrochemistry
2501:
2496:
2481:
2480:
2421:
2408:10.1086/379062
2384:(2): 1061–75.
2368:
2307:
2254:
2230:
2195:
2134:
2121:10.1086/431669
2081:
2054:
2017:(2): 597–611.
2001:
1953:
1939:
1912:
1881:
1869:
1842:
1783:
1729:
1710:
1690:
1622:
1600:
1553:
1514:
1487:
1467:
1432:
1391:
1376:
1335:
1328:
1301:
1257:
1255:
1252:
1251:
1250:
1239:
1228:
1217:
1206:
1195:
1184:
1173:
1162:
1151:
1140:
1129:
1116:
1113:
1112:
1111:
1103:
1100:
1087:
1084:
1047:
1044:
1035:
1032:
1022:
1019:
1011:can result in
988:
985:
953:
950:
917:Star formation
915:Main article:
912:
909:
872:
869:
864:
861:
855:
852:
805:
802:
800:
797:
786:magnetic-state
774:linear fashion
761:
758:
723:
720:
702:
699:
686:
685:Line narrowing
683:
674:
671:
661:
658:
648:
647:
598:
596:
589:
583:
580:
576:
575:
570:
563:
557:
551:
547:
544:
541:
538:
533:
529:
526:
521:
517:
512:
508:
503:
499:
494:
484:
481:
472:
469:
461:
389:
386:
384:
381:
346:magnetic field
332:
329:
231:Charles Townes
205:regeneratively
164:
161:
99:
96:
91:Main article:
88:
85:
9:
6:
4:
3:
2:
2516:
2505:
2502:
2500:
2497:
2495:
2492:
2491:
2489:
2476:
2472:
2467:
2462:
2458:
2454:
2449:
2444:
2441:(3): 958–62.
2440:
2436:
2432:
2425:
2417:
2413:
2409:
2405:
2401:
2397:
2392:
2387:
2383:
2379:
2372:
2364:
2360:
2356:
2352:
2348:
2344:
2340:
2336:
2331:
2326:
2322:
2318:
2311:
2303:
2299:
2295:
2294:10.1038/22972
2291:
2287:
2283:
2278:
2273:
2269:
2265:
2258:
2244:
2240:
2234:
2226:
2222:
2218:
2214:
2211:(1): 625–76.
2210:
2206:
2199:
2191:
2187:
2183:
2179:
2175:
2171:
2166:
2161:
2157:
2153:
2149:
2145:
2138:
2130:
2126:
2122:
2118:
2114:
2110:
2105:
2100:
2097:(1): 220–71.
2096:
2092:
2085:
2077:
2073:
2069:
2065:
2058:
2050:
2046:
2042:
2038:
2034:
2030:
2025:
2020:
2016:
2012:
2005:
1997:
1993:
1989:
1985:
1981:
1977:
1973:
1969:
1965:
1957:
1949:
1943:
1935:
1931:
1927:
1923:
1916:
1908:
1904:
1900:
1896:
1892:
1885:
1878:
1873:
1865:
1861:
1857:
1853:
1846:
1838:
1834:
1829:
1824:
1820:
1816:
1811:
1806:
1802:
1798:
1794:
1787:
1779:
1775:
1771:
1767:
1763:
1759:
1754:
1749:
1745:
1741:
1733:
1727:
1723:
1720:
1714:
1703:
1702:
1694:
1686:
1682:
1678:
1674:
1670:
1666:
1662:
1658:
1653:
1648:
1645:(5): 053901.
1644:
1640:
1633:
1626:
1618:
1611:
1604:
1596:
1592:
1588:
1584:
1580:
1576:
1572:
1568:
1564:
1557:
1549:
1545:
1541:
1537:
1533:
1529:
1525:
1518:
1510:
1506:
1502:
1498:
1491:
1480:
1479:
1471:
1463:
1459:
1455:
1451:
1447:
1443:
1436:
1427:
1422:
1418:
1414:
1410:
1406:
1402:
1395:
1388:
1385:
1380:
1371:
1366:
1362:
1358:
1354:
1350:
1346:
1339:
1331:
1325:
1321:
1320:
1315:
1311:
1305:
1297:
1293:
1289:
1285:
1281:
1277:
1273:
1269:
1262:
1258:
1248:
1243:
1240:
1237:
1232:
1229:
1226:
1225:Astrophys. J.
1221:
1218:
1215:
1210:
1207:
1204:
1203:Astrophys. J.
1199:
1196:
1193:
1188:
1185:
1182:
1177:
1174:
1171:
1170:Astrophys. J.
1166:
1163:
1160:
1159:Astrophys. J.
1155:
1152:
1149:
1144:
1141:
1138:
1133:
1130:
1127:
1122:
1119:
1118:
1109:
1106:
1105:
1099:
1097:
1092:
1083:
1081:
1077:
1073:
1071:
1067:
1063:
1062:proper motion
1059:
1054:
1053:Doppler shift
1043:
1040:
1031:
1028:
1018:
1016:
1015:
1010:
1006:
1002:
998:
994:
984:
982:
978:
970:
966:
962:
958:
949:
947:
943:
939:
935:
931:
927:
923:
918:
908:
904:
902:
897:
889:
885:
882:
881:Mira variable
877:
868:
860:
851:
849:
845:
840:
838:
833:
829:
824:
822:
818:
814:
810:
796:
794:
789:
788:transitions.
787:
783:
779:
778:Zeeman effect
775:
771:
767:
757:
755:
751:
747:
743:
739:
735:
731:
730:
719:
717:
713:
709:
698:
696:
692:
682:
680:
670:
668:
657:
655:
644:
641:
633:
623:
619:
615:
609:
608:
604:
599:This section
597:
593:
588:
587:
579:
574:
571:
568:
564:
561:
558:
555:
552:
545:
542:
539:
537:
530:
524:
518:
516:
509:
507:
500:
498:
495:
493:
490:
489:
488:
480:
478:
468:
467:
459:
455:
451:
446:
444:
439:
437:
436:
429:
427:
423:
419:
414:
412:
408:
404:
399:
395:
380:
378:
374:
370:
366:
365:stellar birth
361:
359:
355:
349:
347:
342:
338:
328:
326:
322:
318:
314:
312:
307:
303:
299:
295:
291:
287:
282:
280:
276:
272:
268:
264:
261:use the term
260:
256:
252:
248:
244:
240:
236:
232:
229:
225:
221:
218:to stand for
217:
212:
210:
206:
202:
198:
194:
190:
186:
180:
178:
174:
171:
160:
158:
154:
150:
147:
143:
140:
136:
132:
128:
124:
123:corresponding
121:
117:
113:
109:
105:
94:
84:
82:
78:
74:
71:
67:
63:
59:
55:
51:
50:spectral line
48:
44:
35:
30:
26:
22:
18:
2438:
2434:
2424:
2381:
2377:
2371:
2320:
2316:
2310:
2267:
2263:
2257:
2246:. Retrieved
2242:
2233:
2208:
2204:
2198:
2147:
2143:
2137:
2094:
2090:
2084:
2063:
2057:
2014:
2010:
2004:
1974:(2): L1–L4.
1971:
1967:
1956:
1942:
1928:(4): 22–23.
1925:
1921:
1915:
1898:
1894:
1884:
1872:
1855:
1851:
1845:
1800:
1796:
1786:
1743:
1739:
1732:
1721:
1718:
1713:
1707:, p. 10
1700:
1693:
1642:
1638:
1625:
1616:
1603:
1570:
1566:
1556:
1531:
1527:
1517:
1500:
1496:
1490:
1477:
1470:
1445:
1441:
1435:
1408:
1404:
1394:
1384:C. H. Townes
1379:
1352:
1348:
1338:
1318:
1304:
1271:
1267:
1261:
1246:
1242:
1235:
1231:
1224:
1220:
1213:
1209:
1205:192 L97–100
1202:
1198:
1191:
1187:
1180:
1176:
1169:
1165:
1158:
1154:
1147:
1143:
1136:
1132:
1125:
1121:
1093:
1089:
1074:
1049:
1038:
1037:
1024:
1012:
990:
974:
946:formaldehyde
928:embedded in
926:H II regions
920:
905:
893:
866:
857:
841:
825:
812:
807:
790:
766:polarisation
763:
760:Polarisation
727:
725:
715:
711:
707:
704:
688:
676:
666:
663:
653:
651:
636:
630:January 2021
627:
612:Please help
600:
577:
486:
477:far infrared
474:
465:
458:formaldehyde
449:
447:
440:
433:
430:
426:Solar System
415:
410:
393:
391:
362:
350:
341:polarisation
334:
320:
309:
305:
297:
285:
283:
278:
262:
246:
242:
238:
234:
227:
223:
219:
215:
213:
188:
181:
176:
169:
166:
163:Nomenclature
115:
101:
42:
40:
1677:10220/18341
1411:(4): 1153.
1387:Nobel Prize
1310:Chu, Steven
1274:: 279–287.
1236:Prog. Phys.
1194:163 1055–57
1172:162 L203–10
1139:213 1109–10
1086:Open issues
1066:Local Group
1034:Variability
997:black holes
782:anisotropic
708:unsaturated
450:anti-pumped
422:OH/IR stars
377:black holes
375:containing
294:astronomers
271:micrometres
255:vibrational
177:single-pass
139:non-thermal
73:atmospheres
2488:Categories
2248:2024-01-07
2239:"M2O Home"
1810:1909.11089
1803:(5): 208.
1746:(2): L33.
1254:References
1227:260 L49–52
1161:189 L31–33
1014:megamasers
844:hydroxides
742:dissociate
734:black body
701:Saturation
695:Lorentzian
556:, SiO, SiO
306:gas lasers
302:physicists
267:wavelength
251:rotational
237:stand for
207:amplified
112:stimulated
87:Background
47:stimulated
2416:120692205
2302:204995005
2160:CiteSeerX
2129:119406933
1996:122403004
1837:202750405
1753:1209.1590
1652:1003.4968
1595:0066-4146
1296:115181195
1247:Astrophys
1183:161 778–9
1150:221 626–8
1128:208 29–31
963:image of
884:S Orionis
848:Hale-Bopp
793:megamaser
712:saturated
601:does not
471:Detection
435:megamaser
383:Discovery
321:microwave
290:terahertz
284:The term
269:of a few
220:microwave
195:or unmet
153:coherence
120:frequency
70:planetary
54:microwave
27:generate
2475:14787000
2363:28172780
2355:15746420
2243:M2O Home
2190:46009823
2182:12089433
2049:17385266
1778:26146516
1685:20867918
1216:15 211–5
1102:See also
1058:NGC 4258
1007:or in a
938:methanol
691:Gaussian
679:velocity
420:, named
403:methanol
398:McKellar
371:and the
360:(VLBI).
239:molecule
209:Ti:Sapph
193:feedback
146:resonant
2453:Bibcode
2396:Bibcode
2335:Bibcode
2317:Science
2282:Bibcode
2213:Bibcode
2152:Bibcode
2144:Science
2109:Bibcode
2072:Bibcode
2029:Bibcode
1976:Bibcode
1903:Bibcode
1860:Bibcode
1815:Bibcode
1758:Bibcode
1657:Bibcode
1575:Bibcode
1536:Bibcode
1505:Bibcode
1503:: 843.
1450:Bibcode
1413:Bibcode
1389:lecture
1357:Bibcode
1276:Bibcode
1192:Science
1181:Science
942:ammonia
832:Jupiter
821:methane
817:ammonia
667:beaming
660:Beaming
622:removed
607:sources
567:MWC 349
311:alcohol
137:into a
125:to the
102:Like a
25:Jupiter
21:Aurorae
2473:
2414:
2361:
2353:
2300:
2264:Nature
2188:
2180:
2162:
2127:
2047:
1994:
1901:: 97.
1835:
1776:
1683:
1593:
1326:
1294:
1148:Nature
1137:Nature
1126:Nature
1001:parsec
965:IC 443
888:masers
819:, and
809:Comets
804:Comets
565:H (in
466:et al.
411:masers
394:et al.
313:lasers
279:lasers
275:optics
263:iraser
173:lasers
149:cavity
135:pumped
127:energy
116:seeded
66:comets
34:Hubble
2471:S2CID
2443:arXiv
2412:S2CID
2386:arXiv
2359:S2CID
2325:arXiv
2298:S2CID
2272:arXiv
2186:S2CID
2125:S2CID
2099:arXiv
2045:S2CID
2019:arXiv
1992:S2CID
1833:S2CID
1805:arXiv
1774:S2CID
1748:arXiv
1705:(PDF)
1647:arXiv
1635:(PDF)
1613:(PDF)
1482:(PDF)
1292:S2CID
1115:Notes
890:(ESO)
830:with
562:, HCN
540:HNCNH
454:dasar
369:death
286:taser
247:maser
243:laser
224:maser
108:maser
104:laser
93:maser
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