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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
HST G1 (Mayall II).jpg
Hubble Telescope image of Mayall II, colour picture assembled from separate images taken in visible and near-infrared wavelengths in July 1994.
Credit: Michael Rich, Kenneth Mighell, and James D. Neill (Columbia University), and Wendy Freedman (Carnegie Observatories) and NASA
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) +13.8[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]
See also: Globular cluster, List of globular clusters

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, having an apparent magnitude of 13.7. 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][4]


Origin of namesEdit

See alsoEdit


  1. ^ a b c d "SIMBAD Astronomical Database". Results for Mayall II. Retrieved 2009-09-13. 
  2. ^ a b Ma, Jun; de Grijs, Richard; Fan, Zhou; Rey, Soo-Chang; Wu, Zhen-Yu; Zhou, Xu; Wu, Jiang-Hua; Jiang, Zhao-Ji; Chen, Jian-Sheng; Lee, Kyungsook; Sohn, Sangmo Tony (June 2009). "RESEARCH PAPER: Old stellar population synthesis: new age and mass estimates for Mayall II = G1". Research in Astronomy and Astrophysics. 9 (6): 641–652. Bibcode:2009RAA.....9..641M. arXiv:0904.0674 . doi:10.1088/1674-4527/9/6/003. 
  3. ^ a b c d e f Ma, J.; de Grijs, R.; Chen, D.; van den Bergh, S.; Fan, Z.; Wu, Z.; Wu, H.; Zhou, X.; Wu, J.; Jiang, Z.; Chen, J. (April 2007). "Structural parameters of Mayall II = G1 in M31". Monthly Notices of the Royal Astronomical Society. 376 (4): 1621–1629. Bibcode:2007MNRAS.376.1621M. arXiv:astro-ph/0702012 . doi:10.1111/j.1365-2966.2007.11573.x. 
  4. ^ Meylan, G.; Sarajedini, A.; Jablonka, P.; Djorgovski, S. G.; Bridges, T.; Rich, R. M. (August 2001). "Mayall II=G1 in M31: Giant Globular Cluster or Core of a Dwarf Elliptical Galaxy?". The Astronomical Journal. 122 (2): 830–841. Bibcode:2001AJ....122..830M. arXiv:astro-ph/0105013 . doi:10.1086/321166. 

External linksEdit