Andromeda Galaxy (M31)
The closest spiral galaxy to the Milky Way.
The Andromeda Galaxy, designated as M31, is the nearest spiral galaxy to Earth, located approximately 2.537 million light-years away in the constellation Andromeda. It is the largest galaxy in the Local Group, which includes the Milky Way, Triangulum Galaxy, and several smaller galaxies. The Andromeda Galaxy is on a collision course with the Milky Way, projected to merge with our galaxy in about 4.5 billion years.
Key Facts
Distance from Earth
2.537 million light-years
Size
Approximately 220,000 light-years in diameter
Number of Stars
Estimated 1 trillion stars
Visibility
Naked eye visible in dark skies without light pollution
Best Viewing Season
Autumn months (September to November)
Best Viewing Time
Late evening to midnight
Best Season
Autumn (September to November)
How to Find It
Locate the constellation Andromeda, which is overhead during autumn evenings. From the prominent 'W' shape of Cassiopeia, draw an imaginary line to the nearest bright star, Mirach (β Andromedae), then move about 1.5 degrees north to find M31.
Observing Tip
Use binoculars or a small telescope to enhance visibility. For astrophotography, use a long exposure time (at least 30 seconds) with proper tracking. Consider using a light pollution filter to capture clearer details.