The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. 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, 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 (1012) stars, at least twice more than the number of stars in our own galaxy, which is estimated to be 200–400 billion. (en.wikipedia.org/wiki/Andromeda_Galaxy).

The image also includes the galaxies M32 (left) and M110 (below to the right).

Date: 12-26-2011 Time: 9pm Location: Sudbury, MA Seeing: Clear Temperature: 29 Fahrenheit, -1.6666666666666667 Celsius Lens: Stellarvue SV105-3SV F7 (735 mm focal length) triplet apochromatic refractor F/stop: f/3.5 with Stellarvue SFF7-3SV Focal Reducer/Flattener Mount: Celestron CGEM Filter: none Camera: Canon T2i/550D unmodified Guide Scope: Stellarvue F50M3 Autoguide: Orion Starshoot + PHD Image Capture: Nebulosity 2 Exposure: 1 hour 20 minutes total; 18 x 3min (180) @ 800 ISO, 4 x 5min (300) @ 800 ISO, 1 x 10min (600) @ 800 ISO Stacking: DeepSkyStacker Image Processing: Adobe Lightroom 3.6 64bit