Mayall II
Hubble Telescope image of Mayall II – colour picture assembled from separate images taken in visible and near-infrared wavelengths in July 1994
Observation data (J2000 epoch)
Right ascension00h 32m 46.51s[1]
Declination+39° 34′ 39.7″[1]
Distance2.52 ± 0.14 Mly (770 ± 40 kpc)
Apparent magnitude (V)+13.81[1]
Physical characteristics
Mass1×107[2] M (2×1037 kg)
Radius21.2 ± 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 designationsSKHB 1, HBK 0-1[1]
See also: Globular cluster, List of globular clusters

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.

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 13.81 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[disambiguation needed] that remains of a dwarf galaxy consumed by Andromeda.[3][4]

Origin of names

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See also


  1. ^ a b c d "NAME Mayall II". SIMBAD. Centre de données astronomiques de Strasbourg. 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. arXiv:0904.0674. Bibcode:2009RAA.....9..641M. doi:10.1088/1674-4527/9/6/003. S2CID 16360116.
  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. arXiv:astro-ph/0702012. Bibcode:2007MNRAS.376.1621M. doi:10.1111/j.1365-2966.2007.11573.x. S2CID 3591548.
  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. arXiv:astro-ph/0105013. Bibcode:2001AJ....122..830M. doi:10.1086/321166. S2CID 17778865.