Andromeda Galaxy (M31)
The nearest spiral galaxy to the Milky Way.
The Andromeda Galaxy, designated M31, is a spiral galaxy approximately 2.537 million light-years from Earth. It is the largest galaxy in the Local Group, which includes the Milky Way, the Triangulum Galaxy, and about 54 other smaller galaxies. M31 is on a collision course with our Milky Way, predicted to merge in about 4.5 billion years.
Key Facts
Distance from Earth
2.537 million light-years
Diameter
220,000 light-years
Apparent Magnitude
+3.44
Visibility
Can be seen with the naked eye under dark skies
Best Time to View
Late summer to early winter (August to December)
Best Season
Late summer through early winter, especially in August through December.
How to Find It
Locate the constellation Andromeda in the northern sky. The Andromeda Galaxy is situated approximately 2.5 degrees northwest of the bright star Alpheratz (α Andromedae). Alternatively, it can be found about 3 degrees from the two brightest stars in the 'W' of Cassiopeia.
Observing Tip
To get the best views, use a telescope with at least a 4-inch aperture, and a dark sky free from light pollution. Use an equatorial mount for astrophotography to track the galaxy effectively during exposure times.