Andromeda Galaxy (M31)
The Nearest Spiral Galaxy to Earth
The Andromeda Galaxy, also known as M31, is the closest spiral galaxy to our Milky Way and the largest galaxy in the Local Group. It contains over a trillion stars and is on a collision course with the Milky Way, expected to merge in about 4.5 billion years.
Key Facts
Distance from Earth
Approximately 2.537 million light-years
Diameter
About 220,000 light-years
Number of Stars
Estimated 1 trillion stars
Visibility
Naked eye visibility under dark skies; apparent magnitude of about 3.44
Best Viewing Season
Fall (northern hemisphere), typically from September to December
Optimal Viewing Time
After sunset until late evening when it's highest in the sky
Best Season
Fall, particularly from September to December for optimal visibility.
How to Find It
Locate the constellation Andromeda in the northern sky. You can identify it using the Great Square of Pegasus — from the square, follow the line connecting the stars to find the two stars (Alpheratz and Mirach) that lead you to M31, which will be roughly located between these two stars.
Observing Tip
For astrophotographers, a telescope with a wide field of view or a good camera on a tripod can capture the beauty of the Andromeda Galaxy. Use longer exposure times to pick up its spiral structure and colors. Try to avoid light pollution and aim for an ideal location with minimal atmospheric disturbance.