Globular Cluster G1 (Mayall II), in the Andromeda Galaxy M31 in Andromeda


Hubble Spies Extragalactic Globular Cluster G1
in the Andromeda Galaxy M31

Right Ascension 00 : 32 : 46.8 (h : m : s)
Declination +39 : 34 : 42 (deg : m: s)
Distance 2900.0 (kly)
Visual Brightness 13.7 (mag)
Hubble Space Telescope has captured a view of a globular cluster called G1, a large, bright ball of light in the center of the photograph consisting of at least 300,000 old stars.

G1, also known as Mayall II, orbits the Andromeda galaxy (M31), the nearest major spiral galaxy to our Milky Way. Located 170,000 light-years from Andromeda's nucleus, G1 is the brightest globular cluster in the Local Group of galaxies. At a distance of 2.9 million light years, it shines at 13.7 mag visual magnitude, and is thus visible as tiny patch in large amateur telescopes. The cluster is also known as SKHB 1 (for Sargent W.L.W., Kowal, C.T., Hartwick, F.D.A., Van Den Bergh, S., who named it G1; Sargent et.al. (1977)), and HBK 0-1 (for Huchra, J.P., Brodie, J.P., Kent, S.M.; Huchra et.al. (1991)).

The crisp image is comparable to ground-based telescope views of similar clusters orbiting the Milky Way. The Andromeda cluster, however, is nearly 100 times farther away (and thus 10,000 times fainter).

A glimpse into the cluster's finer details allow astronomers to see its fainter helium-burning stars whose temperatures and brightnesses show that this cluster in Andromeda and the oldest Milky Way clusters have approximately the same age. These clusters probably were formed shortly after the beginning of the universe, providing astronomers with a record of the earliest era of galaxy formation.

During the next two years, astronomers will use Hubble to study about 20 more globular clusters in Andromeda.

The color picture was assembled from separate images taken in visible and near-infrared wavelengths taken in July of 1994.

Credit: Image and parts of text: Michael Rich, Kenneth Mighell, and James D. Neill (Columbia University), and Wendy Freedman (Carnegie Observatories), and NASA. Data and informations: Leos Ondra

Of this image, high resolution (300 dpi) JPEG images are available in color [722k] and black&white [552 k].

  • SIMBAD Data for G1
  • NED data for G1


    More HST images of M31:

    Hartmut Frommert
    Christine Kronberg

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    Last Modification: 3 Jul 1999