Andromeda Galaxy (M31)
The nearest spiral galaxy to the Milky Way.
M31, also known as the Andromeda Galaxy, is the nearest spiral galaxy to our own Milky Way and is on a collision course with it. It is a massive galaxy, containing approximately one trillion stars and is part of the Local Group of galaxies, which includes the Milky Way, the Triangulum Galaxy, and about 54 other smaller galaxies.
Key Facts
Distance from Earth
2.537 million light-years
Diameter
220,000 light-years
Apparent Magnitude
3.44
Right Ascension
00h 42m 44s
Declination
+41° 16' 9"
Best Season
The best time to view M31 is during fall and winter months, particularly in September through December, when it is high in the sky after sunset.
How to Find It
To locate M31, start by finding the constellation Andromeda in the night sky. The constellation is northeast of Pegasus. M31 is located roughly between the two stars of Andromeda, Alpha Andromedae (Alpheratz) and Beta Andromedae (Mirach). A simple way to find it is to measure about 2.5 times the distance between these two stars in a straight line toward Mirach. Alternatively, you can also use the Great Square of Pegasus to guide you: draw an imaginary line from the star Alpheratz to the lower left, which will lead you to M31.
Observing Tip
For the best results, use binoculars or a telescope to enhance visibility. Look for a faint, elongated smudge of light that is the core of the galaxy. To capture astrophotography images, use a camera with a long exposure time (30 seconds to 2 minutes) with a sturdy mount to avoid any motion blur. A dark site away from city lights will greatly improve your chances of capturing the galaxy.