The Andromeda Galaxy
Following a number of requests for information about the Great Galaxy in
Andromeda, this page has been put together to list some details about it.
Although challenged by the large galaxy in Triangulum (M33), the Andromeda
Galaxy is generally regarded as the most distant object visible to the human
eye. At a distance of 2.52 million light years,
it appears as a fuzzy patch of light in the night sky. In fact, only the bright
core of the galaxy is seen, the full extent of the galaxy covers over 3° of sky
on its longest side.
The galaxy is the largest member of the Local Group, a group of about 30
galaxies that includes both our own Milky Way and M33. It contains
approximately twice the number of stars as our Galaxy and is about 125,000
light years in diameter. It is a spiral galaxy of type Sb (a spiral with fairly
tight wound arms) inclined at an angle of 15° to our line of sight. Like our
Galaxy, it has two prominent satellite galaxies, M32 and NGC 205, both of which
are small ellipticals.
Observations with the Hubble Space Telescope suggest that the Andromeda Galaxy
may have two cores. This is thought to be the result of a past merger with
another galaxy. Such processes were once common in the Universe and still occur
today. Indeed, the galaxy is approaching us at a speed of 68 kilometres per
second and a collision with the Milky Way is a possibility in the distant
future.
Some star charts show a star designated S Andromedae close to the galaxy's
position. This was a supernova seen to
erupt in the galaxy in 1885. It reached magnitude
6 before fading away the following year.
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