Andromeda Galaxy
The nearest spiral galaxy to the Milky Way.
M31, known as the Andromeda Galaxy, is a spiral galaxy approximately 2.537 million light-years from Earth. It is the closest spiral galaxy to our own Milky Way and is visible to the naked eye in the constellation Andromeda. M31 is a massive galaxy, containing about one trillion stars and has a diameter of about 220,000 light-years, making it significantly larger than the Milky Way.
Key Facts
Distance from Earth
2.537 million light-years
Diameter
220,000 light-years
Apparent Magnitude
+3.44 (naked eye)
Type
Spiral galaxy (SA(s)b)
Best Season
Best viewed during the fall and early winter months (September to January), ideally on clear, dark nights with minimal light pollution.
How to Find It
To locate the Andromeda Galaxy, first find the constellation Cassiopeia, shaped like a 'W'. From there, draw an imaginary line to the Great Square of Pegasus, or identify the stars Mirach (Beta Andromedae) and Mu Andromedae. The Andromeda Galaxy lies approximately 25 degrees from Mirach, toward the northeast.
Observing Tip
Astrophotographers should use a telescope with a focal length of at least 600mm for detailed images. Use a mount capable of tracking the galaxy to avoid star trails. A longer exposure and stacking multiple images taken over several minutes can enhance detail and reduce noise.