Messier 73
Messier73 | |
---|---|
![]() Asterism Messier 73 in Aquarius | |
Observation data (J2000epoch) | |
Right ascension | 20h58m54s[1] [2] |
Declination | −12° 38′[1][2] |
Distance | Mean distance star approx. 1685ly[3](approx. 516.6pc) |
Apparent magnitude(V) | 9.0[1][2] |
Apparent dimensions (V) | 2.8′[2] |
Physical characteristics | |
Radius | ly |
Estimated age | million yrs[citation needed] |
Other designations | M 73,NGC6994,[1][2]Cr426 |
Associations | |
Constellation | Aquarius |
Messier 73(M73,also known asNGC 6994) is anasterismof fourstarsin the constellationAquarius.It lies several arcminutes east of globular clusterM72.According toGaia EDR3,the stars are1030±9,1249±10,2170±22,and2290±24light-years from the Sun, with the second being a binary star.[4]
History
[edit]M73 was discovered byCharles Messierin 1780[a]who originally described the object as aclusterof four stars with some nebulosity. Much later observations byJohn Herschelcould not find any nebulosity. Moreover, Herschel noted that the designation of M73 as a cluster was questionable. Nonetheless, Herschel included M73 in hisGeneral Catalogueof clusters,nebulae,andgalaxies,andJohn Dreyerincluded M73 when he compiled theNew General Catalogue.[5]
Relation between the stars
[edit]M73 was once treated as a potential sparsely populatedopen cluster,which consists of stars that are physically associated in space as well as on the sky. The question of whether the stars were an asterism or an open cluster was a matter of debate in the early 2000s.
In 2000, L. P. Bassino, S. Waldhausen, and R. E. Martinez published an analysis of the colors and luminosities of the stars in and around M73. They concluded that the four bright central stars and some other nearby stars followed the color-luminosity relation that is also followed by stars in open clusters (as seen in aHertzsprung–Russell diagram). Their conclusion was that M73 was an old open cluster that was 9′wide.[6]However, G. Carraro, published results in 2000 based on a similar analysis and concluded that the stars did not follow any color-luminosity relation. Carraro's conclusion was that M73 was an asterism.[7]Adding to the controversy, E. Bica and collaborators concluded that the chance alignment of the four bright stars seen in the center of M73 as well as one other nearby star was highly unlikely, so M73 was probably a sparse open cluster.[8]The controversy was resolved in 2002, when M. Odenkirchen and C. Soubiran published an analysis of the high resolutionspectraof the six brightest stars within 6′of the centre point. They demonstrated that the distances from the Earth to the six stars were very different from each other, and the stars were moving in different directions. Therefore, they concluded that the stars were only an asterism.[9]
Although M73 was determined to be only a chance alignment of stars, further analysis of asterisms is still important for the identification of sparsely populated open clusters. A full study of very many such clusters would demonstrate how, how often, and to what degree open clusters are ripped apart by thegravitational forcesin theMilky Wayand reveal more of the sources ofthese forces.
Location
[edit]![](https://upload.wikimedia.org/wikipedia/commons/thumb/d/d2/Aquarius_constellation_map.svg/250px-Aquarius_constellation_map.svg.png)
See also
[edit]- List of Messier objects
- Messier 40-a double star included in theMessier cataloguethat was also mistakenly identified as having nebulosity
Notes and references
[edit]- ^on October 4
- ^abcd "M 73".SIMBAD.Centre de données astronomiques de Strasbourg.Retrieved2006-12-21.
- ^abcde "Messier 73".SEDS Messier pages.Retrieved2010-02-28.
- ^Brown, A. G. A.;et al. (Gaia collaboration) (2021)."GaiaEarly Data Release 3: Summary of the contents and survey properties ".Astronomy & Astrophysics.649:A1.arXiv:2012.01533.Bibcode:2021A&A...649A...1G.doi:10.1051/0004-6361/202039657.S2CID227254300.(Erratum:doi:10.1051/0004-6361/202039657e).
- ^Brown, A. G. A.;et al. (Gaia collaboration) (2021)."GaiaEarly Data Release 3: Summary of the contents and survey properties ".Astronomy & Astrophysics.649:A1.arXiv:2012.01533.Bibcode:2021A&A...649A...1G.doi:10.1051/0004-6361/202039657.S2CID227254300.(Erratum:doi:10.1051/0004-6361/202039657e).
- ^ K. G. Jones (1991).Messier's Nebulae and Star Clusters(2nd ed.).Cambridge University Press.ISBN978-0-521-37079-0.
- ^ L. P. Bassino; S. Waldhausen & R. E. Martinez (2000). "CCD photometry in the region of NGC 6994: The remains of an old open cluster".Astronomy & Astrophysics.355:138–144.arXiv:astro-ph/0001238.Bibcode:2000A&A...355..138B.
- ^ G. Carraro (2000). "NGC 6994: An open cluster which is not an open cluster".Astronomy & Astrophysics.357:145–148.arXiv:astro-ph/0003372.Bibcode:2000A&A...357..145C.
- ^ E. Bica; B. X. Santiago; C. M. Dutra; H. Dottori; M. R. de Oliveira & D. Pavani (2001). "Dissolving star cluster candidates".Astronomy & Astrophysics.366(3): 827–833.arXiv:astro-ph/0011280.Bibcode:2001A&A...366..827B.doi:10.1051/0004-6361:20000248.S2CID10979809.
- ^ M. Odenkirchen & C. Soubiran (2002). "NGC 6994: Clearly not a physical stellar ensemble".Astronomy & Astrophysics.383(1): 163–170.arXiv:astro-ph/0111601.Bibcode:2002A&A...383..163O.doi:10.1051/0004-6361:20011730.S2CID15545816.
External links
[edit]![](https://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)