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The Andromeda Galaxy is cataloged as M31 and NGC 224, and is the closest large galaxy to the “Milky Way” and the only one visible to the naked eye in the Northern Hemisphere. It was first known to the Persian Astronomer Al-Sufi about 905 AD who described it 964 AD in his “Book of fixed Stars” as “Little Cloud”. It is also known as the “Great Nebula” in Andromeda and is part of the “Local Group” of several galaxies that include the Milky Way, wich it resembles in shape and composition. It has a distance to us of Aprox. 2.2 to 2.9 Million light-years , a disk diameter of between 165,000-200,000 light years, contains at least 200 billion stars, and it’s mass was estimated at about 300 to 400 billion times that of our Sun, wich makes it still considerably less dense than our Milky Way galaxy wich has a solar mass of between 750 billion and one trillion. It’s two brightest companion galaxies are M32 and M110. The light arriving at Earth from the Andromeda Galaxy is shifted toward the blue end of the spectrum,
whereas the light from other cosmic sources exhibits red shift.
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