The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion (10 12) stars: at least twice the number of stars in the Milky Way galaxy, which is estimated to be 200–400 billion. The Andromeda Galaxy is the largest galaxy of the Local Group, which also contains the Milky Way, theTriangulum Galaxy, and about 30 other smaller galaxies. It gets its name from the area of the sky in which it appears, the constellation of Andromeda, which was named after the mythological princess Andromeda. The Andromeda Galaxy is the nearest spiral galaxy to our Milky Waygalaxy, but not the nearest galaxy overall. Also known as Messier 31, M31, or NGC 224, it is often referred to as the Great Andromeda Nebula in older texts.
