Messier 54

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Messier 54 (or M54 or NGC 6715) is a globular cluster in the constellation Sagittarius. It was discovered by Charles Messier in 1778. Later, he included it in his catalog of comet-like objects.

M54 was thought to belong to our Milky Way galaxy, but in 1994 it was discovered that M54 belongs to the Sagittarius dwarf elliptical galaxy ('Sag DEG'),[1]

M54 is some 87,000 light-years from us, and has a radius of 150 light-years across. It is one of the most dense globulars. It shines with the luminosity of roughly 850,000 times that of the Sun and has an absolute magnitude of −10.0.

M54 is easily found in the sky, being close to the star ζ Sagittarii. Individual stars cannot be seen with amateur telescopes.

It is on or near SagDEG's center. Some authors think it actually may be its core;[2] but others do not.[3]

In July 2009, a team of astronomers found evidence of a medium-sized black hole in the core of M54.[4]

References[change | change source]

  1. Siegel, Michael H. et al (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. doi:10.1086/522003. 
  2. Carretta E. et al (2010). "M54 + Sagittarius = ω Centauri". The Astrophysical Journal Letters 714 (1): L7–L11. doi:10.1088/2041-8205/714/1/L7. 
  3. Bellazzini M. et al (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. doi:10.1088/0004-6256/136/3/1147. 
  4. Ibata, R. et al (2009). "Density and kinematic cusps in M54 at the heart of the Sagittarius Dwarf Galaxy: evidence for a mass 104 (x Sun's mass) black hole?". Astrophysical Journal Letters 699 (2): L169–L173. doi:10.1088/0004-637X/699/2/L169.