Messier 54 Explained
| Messier 54 |
| Epoch: | J2000 |
| Class: | III |
| Constellation: | Sagittarius |
| Dist Ly: | 87.4abbr=onNaNabbr=on |
| Appmag V: | 7.6[1] |
| Size V: | 12.0 |
| Radius Ly: | 153 ly[2] |
| Age: | 13 Gyr[3] |
| Notes: | Probably extragalactic |
| Names: | M54, NGC 6715, GCl 104, C 1851-305 |
Messier 54 (also known as M54 or NGC 6715) is a globular cluster in the constellation Sagittarius. It was discovered by Charles Messier in 1778 and then included in his catalog of comet-like objects.
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.[4]
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),[5] 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 more than two centuries. As it is located in SagDEG's center, some authors think it actually may be its core;[6] 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.[7]
Modern estimates now place M54 at a distance of some 87,000 light-years, translating into a true radius of 150 light-years across.[2] It is one of the denser of the globulars, being of class III (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.
See also
External links
Notes and References
- Web site: Messier 54 . 29 April 2022 . SEDS Messier Catalog.
- From trigonometry: radius = distance × sin(diameter_angle / 2) = 153 ly.
- Geisler . Doug . Wallerstein . George . Smith . Verne V. . Casetti-Dinescu . Dana I. . 2007 . Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo . . 119 . 859 . 939–961 . 2007PASP..119..939G . 10.1086/521990. 0708.0570 . 119599242 .
- Ibata . R. . Bellazzini . M. . Chapman . S. C. . Dalessandro . E. . Ferraro . F. . Irwin . M. . Lanzoni . B. . Lewis . G. F. . Mackey . A. D. . Miocchi . P. . Varghese . A. . 4 . 2009 . Density and Kinematic Cusps in M54 at the Heart of the Sagittarius Dwarf Galaxy: Evidence for a Black Hole? . . 699 . 2 . L169–L173 . 0906.4894 . 2009ApJ...699L.169I . 10.1088/0004-637X/699/2/L169. 15976588 .
- Siegel . Michael H. . 4 . Dotter . Aaron . Majewski . Steven R. . Sarajedini . Ata . Chaboyer . Brian . Nidever . David L. . Anderson . Jay . Marín-Franch . Antonio . Rosenberg . Alfred . 2007 . The ACS Survey of Galactic Globular Clusters: M54 and Young Populations in the Sagittarius Dwarf Spheroidal Galaxy . . 667 . 1 . L57–L60 . 2007ApJ...667L..57S . 10.1086/522003. 0708.0027 . Bedin . Luigi R. . Aparicio . Antonio . King . Ivan . Piotto . Giampaolo . Reid . I. Neill . 119626792 .
- Carretta, E. . 4 . Bragaglia, A. . Gratton, R. G. . Lucatello, S. . Bellazzini, M. . Catanzaro, G. . Leone, F. . Momany, Y. . Piotto, G. . D'Orazi, V. . M54 + Sagittarius = ω Centauri . The Astrophysical Journal Letters . 2010 . 714 . 1 . L7–L11 . 2010ApJ...714L...7C . 10.1088/2041-8205/714/1/L7. 1002.1963 . 118440761 .
- Bellazzini, M. . 4 . Ibata, R. A. . Chapman, S. C. . Mackey, A. D. . Monaco, L. . Irwin, M. J. . Martin, N. F. . Lewis, G. F. . Dalessandro, E. . The Nucleus of the Sagittarius Dsph Galaxy and M54: a Window on the Process of Galaxy Nucleation . The Astronomical Journal . 2008 . 136 . 3 . 1147–1170 . 2008AJ....136.1147B . 10.1088/0004-6256/136/3/1147. 0807.0105 . 53486171 .
