View source for Messier Index/M54

{{ Globular cluster |
| name = [[w:Messier object|Messier]] 54
| image = [[image:Messier 54 Hubble WikiSky.jpg|250px]]
| caption = M54 by [[w:Hubble Space Telescope]]; 3.5&prime; view
| credit = [[w:NASA]]/[[w:STScI]]/[[w:WikiSky]]
| epoch = [[w:J2000]]
| class = III
| constellation = [[w:Sagittarius (constellation)|Sagittarius]]
| ra = {{RA|18|55|03.28}}<ref name="simbad">{{cite web
  | title=SIMBAD Astronomical Database
  | work=Results for NGC 6715
  | url=http://simbad.u-strasbg.fr/Simbad
  | accessdate=2006-11-16}}</ref>
| dec = {{DEC|-30|28|42.6}}<ref name="simbad" />
| dist_ly = 87.4 [[w:light-year|kly]]<ref>[http://arxiv.org/abs/astro-ph/0510217v1 Gavin Ramsay and Kinwah Wu, Chandra observations of the globular cluster M54]</ref>
| dist_pc = 26.8 [[w:parsec|kpc]]
| appmag_v = 8.37<ref name="simbad" />
| size_v = 12&prime;.0
| mass_kg = 
| mass_msol = 
| radius_ly = 153 ly<ref>distance &times; sin( diameter_angle / 2 ) = 153 ly. radius</ref>
| v_hb = 
| age = 13 Gyr<ref name="Geisleretal2007">{{citation
 | last1 = Geisler
 | first1 = Doug
 | last2 = Wallerstein
 | first2 = George
 | last3 = Smith
 | first3 = Verne V.
 | last4 = Casetti-Dinescu
 | first4 = Dana I.
 | title = Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo
 | year = 2007
 | date = September 2007
 | journal = The Publications of the Astronomical Society of the Pacific
 | volume = 119
 | issue = 859
 | page = 939-961
 | url = http://adsabs.harvard.edu/abs/2007PASP..119..939G
 | doi = 10.1086/521990
}}</ref>
| notes = Probably extragalactic
| names = M54,<ref name="simbad" /> [[w:New General Catalogue|NGC]] 6715,<ref name="simbad" /> GCl 104<ref name="simbad" />
}}
{{commonscat|Messier 54}}

'''Messier 54''' (also known as '''M54''' or '''NGC 6715''') is a [[w:globular cluster]] in the [[w:constellation]] [[w:Sagittarius (constellation)|Sagittarius]]. It was discovered by [[w:Charles Messier]] in [[w:1778]] and subsequently included in his catalog of [[w:comet]]-like objects.

Previously thought to be at a distance from [[w:Earth]] of about 50,000 [[w:light-year]]s, it was discovered in [[w:1994]] that M54 was most likely not part of the [[w:Milky Way]], but actually part of the [[w:Sagittarius Dwarf Elliptical Galaxy]], (''SagDEG''),<ref name="Siegeletal2007">{{citation
 | last1 = Siegel
 | first1 = Michael H.
 | last2 = Dotter
 | first2 = Aaron
 | last3 = Majewski
 | first3 = Steven R.
 | last4 = Sarajedini
 | first4 = Ata
 | last5 = Chaboyer
 | first5 = Brian
 | last6 = Nidever
 | first6 = David L.
 | last7 = Anderson
 | first7 = Jay
 | last8 = Marín-Franch
 | first8 = Antonio
 | last9 = Rosenberg
 | first9 = Alfred
 | last10 = Bedin
 | first10 = Luigi R.
 | last11 = Aparicio
 | first11 = Antonio
 | last12 = King
 | first12 = Ivan
 | last13 = Piotto
 | first13 = Giampaolo
 | last14 = Reid
 | first14 = I. Neill
 | title = The ACS Survey of Galactic Globular Clusters: M54 and Young Populations in the Sagittarius Dwarf Spheroidal Galaxy
 | url = http://adsabs.harvard.edu/cgi-bin/bib_query?bibcode=2007ApJ...667L..57S
 | year = 2007
 | date = September 2007
 | journal = The Astrophysical Journal
 | volume = 667
 | issue = 1
 | page = L57-L60
 | doi = 10.1086/522003
}}</ref> making it the first [[w:Extragalactic astronomy|extragalactic]] globular cluster ever discovered, even if it wasn't recognized as such for nearly two and a quarter centuries.

Modern estimates now place M54 at a distance of some 87,000 light-years, translating into a true radius of 150 light-years across. 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 [[w:luminosity]] of roughly 850,000 times that of the [[w:Sun]] and has an [[w:absolute magnitude]] of -10.0.

M54 is easily found on the sky, being close to the [[w:star]] [[w:Zeta Sagittarii|ζ Sagittarii]]. It is however, not resolvable into individual stars even with larger amateur [[w:telescope]]s.

In July of 2009, a team of astronomers reported that they had found evidence of an [[w:intermediate-mass black hole]] in the core of M54.<ref name="Ibata2009">{{citation
 | last1 = Ibata
 | first1 = R.
 | last2 = Bellazzini
 | first2 = M.
 | last3 = Chapman
 | first3 = S. C.
 | last4 = Dalessandro
 | first4 = E.
 | last5 = Ferraro
 | first5 = F.
 | last6 = Irwin
 | first6 = M.
 | last7 = Lanzoni
 | first7 = B.
 | last8 = Lewis
 | first8 = G. F.
 | last9 = Mackey
 | first9 = A. D.
 | last10 = Miocchi
 | first10 = P.
 | last11 = Varghese
 | first11 = A.
 | title = Density and Kinematic Cusps in M54 at the Heart of the Sagittarius Dwarf Galaxy: Evidence for A <math>10^4 M_{sun}</math> Black Hole?
 | year = 2009
 | date = July 2009
 | journal = The Astrophysical Journal Letters
 | volume = 699
 | issue = 2
 | page = L169-L173
 | url = http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:0906.4894
 | doi = 10.1088/0004-637X/699/2/L169
}}</ref>  This was the first report of such a black hole in any globular cluster.

==External links==
* [http://www.seds.org/messier/m/m054.html M54 @ SEDS Messier pages]

==References==
{{reflist}}

{{Messier Index}}