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Andromeda
from Issue #4 November 2003
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The Andromeda Galaxy or M31
In October the Andromeda galaxy moved into view for most inhabitants of the northern hemisphere. Often referred to as M31, Andromeda is the closest major galaxy to our own Milky Way. Andromeda is a spiral galaxy and it is very close to our own galaxy's shape and size.
To locate Andromeda, look to the northeast just after sunset. You will need a very dark clear sky and preferably a new moon. The galaxy looks like a dim haze of lights, larger in diameter than a full moon.
Abd-al-Rahman Al Sufi of Persia first discovered Andromeda in 964 A.D. He called Andromeda “a little cloud” and wrote about the galaxy in his book, "Book of Fixed Stars." In Europe Al Sufi's observations were not known and Simon Marius rediscovered Andromeda in 1612 with a moderate telescope.
Andromeda is one of over 30 galaxies that make up our local group. These galaxies are spread out and have approximately a 10 million light year diameter. The group's center is thought to be somewhere between the Milky Way and Andromeda. These two galaxies are by far the most massive of the local group. Their strong gravity acts upon smaller surrounding galaxies and the result is an accumulated system of satellite galaxies.
Although Andromeda is considered to be close to our own galaxy, it is actually over 2 million light years away. Other galaxies in our local group are between 88,000 light years and 8 million lights away from the Milky Way. There are other groups of galaxies in addition to our own local group, the closest being the Virgo Cluster. This group contains over 2000 galaxies and dominates our galactic neighborhood. Most experts estimate the edge of the Virgo cluster to be at least 60 million light years away.
With the sheer size of our known universe, the possibility of life beyond our own planet is astonishing. The Milky Way alone has approximately 400 billion stars. Multiply this by the thousands if not millions of other galaxies in the universe and it's hard for any person to truly grasp the size and dimension of our universe. New planets are being found every day. It's only a matter of time before earth-like planets are discovered.
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