Andromeda Galaxy (M31)
The nearest spiral galaxy to the Milky Way.
The Andromeda Galaxy, also known as M31, is the closest spiral galaxy to our own Milky Way, located approximately 2.537 million light-years away. It is on a collision course with the Milky Way, predicted to merge with our galaxy in about 4.5 billion years. M31 is visible to the naked eye from dark locations and is a popular target for amateur astronomers and astrophotographers.
Key Facts
Distance from Earth
Approximately 2.537 million light-years
Diameter
About 220,000 light-years
Brightness (Magnitude)
Approximately +3.44
Visibility
Naked eye; recommended viewing under dark skies
Best viewing times
Fall (September to December), particularly in October
Colliding with Milky Way
Expected to collide in about 4.5 billion years
Best Season
Best seen during the fall months (September to December), especially October.
How to Find It
To locate M31, start by finding the Great Square of Pegasus, which consists of four bright stars forming a square. From the eastern corner of the square, extend a line roughly 2.5 degrees in a direction towards the constellation Andromeda. Look for a faint glow of light about 2.5 times the width of the square, which is the Andromeda Galaxy.
Observing Tip
For best results, use a telescope or binoculars, but you can also see it with the naked eye under dark skies. For astrophotography, use a camera mounted on a tripod, set long exposures (15-30 seconds), and take multiple shots to stack for greater detail later.