M31 Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. Andromeda is the nearest spiral galaxy to the Milky Way, but not the closest galaxy overall. It gets its name from the area of the sky in which it appears, the Andromeda constellation, which was named after the mythological princess Andromeda. Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way, the Triangulum Galaxy M33, and about 30 other smaller galaxies. Although the largest, Andromeda may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping.The 2006 observations by the Spitzer Space Telescope revealed that M31 contains one trillion stars: at least twice the number of stars in our own galaxy, which is estimated to be c. 200–400 billion.
A 2009 study estimated that the Milky Way and Andromeda are about equal in mass, while a 2006 study put the mass of the Milky Way at ~80% of the mass of Andromeda. The Andromeda Galaxy and the Milky Way are expected to collide in perhaps 4.5 billion years.
At lower right is the satellite balaxy M110, with about 10 billion suns
At centre left is satellite galaxy M32.
Orion Optics UK AG16 Astrograph: SBIG 11000 CM: Titan Mount
25 x 4 minutes
Data capture 23rd January 2012