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Group of stars in the constellation Andromeda From Wikipedia, the free encyclopedia
Mayall II, also known as NGC-224-G1, SKHB 1, GSC 2788:2139, HBK 0-1, M31GC J003247+393440 or Andromeda's Cluster, is a globular cluster orbiting M31, the Andromeda Galaxy.
Mayall II | |
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![]() Hubble Telescope image of Mayall II | |
Observation data (J2000 epoch) | |
Constellation | Andromeda |
Right ascension | 00h 32m 46.51s[1] |
Declination | +39° 34′ 39.7″[1] |
Distance | 2.52 ± 0.14 Mly (770 ± 40 kpc) |
Apparent magnitude (V) | +13.81[1] |
Physical characteristics | |
Mass | 1×107[2] M☉ (2×1037 kg) |
Radius | 21.2 ± 1.0 ly (6.5 ± 0.3 pc) (Half light radius rh) and tidal radius 263.2 ± 12.7 ly (80.7 ± 3.9 pc)[3] |
Estimated age | ~ 12 Gyr[2] |
Other designations | SKHB 1, HBK 0-1[1] |
It is located 130,000 light-years (40 kpc)[3] from the Andromeda Galaxy's galactic core, and is the brightest[3] (by absolute magnitude) globular cluster in the Local Group, with an absolute visual magnitude of -10.94 and the luminosity of 2 million Suns.[4] It has an apparent magnitude of 13.81 in V band. Mayall II is considered to have twice the mass of Omega Centauri, and may contain a central, intermediate-mass (~ 2×104 M⊙) black hole.[3]
It was first identified as a possible globular cluster by American astronomers Nicholas Mayall and Olin J. Eggen in 1953 using a Palomar 48-inch (1.2 m) Schmidt plate exposed in 1948.[3]
Because of the widespread distribution of metallicity, indicating multiple star generations and a large stellar creation period, many contend that it is not a true globular cluster, but is actually the galactic core that remains of a dwarf galaxy consumed by Andromeda.[3][5]