It is easily found in the sky, being close to thestarζ Sagittarii. It is, however, not resolvable into individual stars even with larger amateurtelescopes.
In July 2009, a team of astronomers reported that they had found evidence of anintermediate-mass black hole in the core of M54.[8]
Previously thought to belong to theMilky Way at a distance fromEarth of about 50,000light-years, it was discovered in 1994 that M54 most likely belongs to theSagittarius 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 more than two 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 bydynamical 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 ofclass III[1] (I being densest and XII being the least dense). It shines with theluminosity of roughly 850,000 times that of theSun and has anabsolute magnitude of −10.0.
^abShapley, Harlow; Sawyer, Helen B. (August 1927). "A Classification of Globular Clusters".Harvard College Observatory Bulletin.849 (849):11–14.Bibcode:1927BHarO.849...11S.
^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.
