It is easily found in the sky, being close to the star ζ Sagittarii. It is, however, not resolvable into individual stars even with larger amateur telescopes.
In July 2009, a team of astronomers reported that they had found evidence of an intermediate-mass black hole in the core of M54.[8]
Distance
Previously thought to belong to the Milky Way at a distance from Earth of about 50,000 light-years, it was discovered in 1994 that M54 most likely belongs to the Sagittarius Dwarf Elliptical Galaxy (SagDEG),[9] making it the first globular cluster formerly thought to be part of our galaxy reassigned to extragalactic status, even if not recognized as such for nearly two and a quarter centuries. As it is located in SagDEG's center, some authors think it actually may be its core;[10] however others have proposed that it is a real globular cluster that fell to the center of this galaxy due to decay of its orbit caused by dynamical friction.[11]
Modern estimates now place M54 at a distance of some 87,000 light-years,[3] translating into a true radius of 150 light-years across.[5] It is one of the denser of the globulars, being of class III[1] (I being densest and XII being the least dense). It shines with the luminosity of roughly 850,000 times that of the Sun and has an absolute magnitude of −10.0.
Shapley, Harlow; Sawyer, Helen B. (August 1927). "A Classification of Globular Clusters". Harvard College Observatory Bulletin. 849 (849): 11–14. Bibcode:1927BHarO.849...11S.
Goldsbury, Ryan; etal. (December 2010). "The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters". The Astronomical Journal. 140 (6): 1830–1837. arXiv:1008.2755. Bibcode:2010AJ....140.1830G. doi:10.1088/0004-6256/140/6/1830.
"M 54". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-16.
Ibata, R.; Bellazzini, M.; Chapman, S. C.; Dalessandro, E.; etal. (2009). "Density and Kinematic Cusps in M54 at the Heart of the Sagittarius Dwarf Galaxy: Evidence for a 104M☉ Black Hole?". Astrophysical Journal Letters. 699 (2): L169–L173. arXiv:0906.4894. Bibcode:2009ApJ...699L.169I. doi:10.1088/0004-637X/699/2/L169.
Siegel, Michael H.; Dotter, Aaron; Majewski, Steven R.; Sarajedini, Ata; etal. (2007). "The ACS Survey of Galactic Globular Clusters: M54 and Young Populations in the Sagittarius Dwarf Spheroidal Galaxy". Astrophysical Journal Letters. 667 (1): L57–L60. arXiv:0708.0027. Bibcode:2007ApJ...667L..57S. doi:10.1086/522003.
Bellazzini, M.; Ibata, R. A.; Chapman, S. C.; Mackey, A. D.; etal. (2008). "The Nucleus of the Sagittarius Dsph Galaxy and M54: a Window on the Process of Galaxy Nucleation". The Astronomical Journal. 136 (3): 1147–1170. arXiv:0807.0105. Bibcode:2008AJ....136.1147B. doi:10.1088/0004-6256/136/3/1147.
Specifically in centre this very mildly southern zone of the sky which is well observable from everywhere except the Arctic Circle. However the Sun, considered from our orbit, passes through this zone throughout December. This also makes the cluster mostly risen during day, not night, in the nearest months.
External links
Wikimedia Commons has media related to Messier 54.
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