M31-G1, Andromeda's largest globular cluster
| G1 or Mayall II, 10 x 1 min Lum, C9.25 f/5, ST10XME with AO8 |
Mayall II (M31 G1), also known as NGC-224-G1 or Andromeda's Cluster, is a globular cluster
orbiting M31, the Andromeda Galaxy. Like our galaxy, Andromeda has numberous globular
clusters orbiting its galactic core. Some estimates put the number at around 500. Robert
Gendler has many of the Andromeda clusters identified on some of his images of M31
(http://www.robgendlerastropics.com/M31NMmosaicglobs.html).
You won't find G1 on Gendler's images, however. G1 is located 130,000 light-years from
Andromeda's galactic core and is off the field of most M31 images. G1 is the brightest (absolute
magnitude) globular cluster in the Local Group. At a distance of 2.9 million light years, it shines at
13.7 visual magnitude, and is thus visible as tiny patch in large amateur telescopes (see
http://www.perezmedia.net/beltofvenus/archives/000512.html). Mayall II is considered to have
twice the mass of Omega Centauri, our galaxy's largest known globular cluster. However since this
Andromeda cluster is nearly 100 times farther away than Omega Centauri it is about 10,000 times
fainter.
G1 was first identified as a possible globular cluster in 1953 using a Palomar 48-inch Schmidt
plate exposed in 1948 (http://en.wikipedia.org/wiki/Nicholas_Mayall ). Some contend that it is not
a true globular cluster, but is actually the galactic core that remains of a dwarf galaxy consumed
by Andromeda. G1 may contain a central, intermediate-mass, black hole.
If you are interested in seeing M31-G1 for yourself, here is the best description I found on how to
find it in the sky: http://astronomerica.awardspace.com/spacewalk-m31.php. I went from
Alpheratz to SAO 54281 to SAO 36699 to SAO 53990 to GSC 2788:2139, centering each star
along the way. With the last star centered, G1 should be close to the center of the field.
Needless to say, I used "The Sky" and GOTO to find this little gem. My image below shows G1
flanked by two stars to form a tiny triangle just below the center of the field. Both stars are in our
galaxy. In fact all of the other stars in this image are part of the Milky Way. A much better image
of G1 is seen in the Hubble Space Telescope image (1996) shown below. Click on either image
for a larger size.
orbiting M31, the Andromeda Galaxy. Like our galaxy, Andromeda has numberous globular
clusters orbiting its galactic core. Some estimates put the number at around 500. Robert
Gendler has many of the Andromeda clusters identified on some of his images of M31
(http://www.robgendlerastropics.com/M31NMmosaicglobs.html).
You won't find G1 on Gendler's images, however. G1 is located 130,000 light-years from
Andromeda's galactic core and is off the field of most M31 images. G1 is the brightest (absolute
magnitude) globular cluster in the Local Group. At a distance of 2.9 million light years, it shines at
13.7 visual magnitude, and is thus visible as tiny patch in large amateur telescopes (see
http://www.perezmedia.net/beltofvenus/archives/000512.html). Mayall II is considered to have
twice the mass of Omega Centauri, our galaxy's largest known globular cluster. However since this
Andromeda cluster is nearly 100 times farther away than Omega Centauri it is about 10,000 times
fainter.
G1 was first identified as a possible globular cluster in 1953 using a Palomar 48-inch Schmidt
plate exposed in 1948 (http://en.wikipedia.org/wiki/Nicholas_Mayall ). Some contend that it is not
a true globular cluster, but is actually the galactic core that remains of a dwarf galaxy consumed
by Andromeda. G1 may contain a central, intermediate-mass, black hole.
If you are interested in seeing M31-G1 for yourself, here is the best description I found on how to
find it in the sky: http://astronomerica.awardspace.com/spacewalk-m31.php. I went from
Alpheratz to SAO 54281 to SAO 36699 to SAO 53990 to GSC 2788:2139, centering each star
along the way. With the last star centered, G1 should be close to the center of the field.
Needless to say, I used "The Sky" and GOTO to find this little gem. My image below shows G1
flanked by two stars to form a tiny triangle just below the center of the field. Both stars are in our
galaxy. In fact all of the other stars in this image are part of the Milky Way. A much better image
of G1 is seen in the Hubble Space Telescope image (1996) shown below. Click on either image
for a larger size.
| Hubble image of M31-G1 (http://hubblesite.org/gallery/album/ exotic/pr2002018c/) |