Great Andromeda Spiral Galaxy
Great Andromeda Spiral Galaxy, also known as M 31, large spiral galaxy in the constellation Andromeda , about 2.2 million light-years from Earth. The Great Andromeda Spiral Galaxy is the largest nearby galactic neighbor to the Milky Way Galaxy, Earth’s home galaxy. Because it is so near, it appears very bright, with a total magnitude (a measure of its brightness as seen from Earth) of 3.4, and is easily visible to the naked eye on a clear, dark night. Its immense diameter of about 200,000 light-years makes it appear five times larger than the full Moon in our sky. The Great Andromeda Spiral Galaxy is the most studied of external galaxies because astronomers can view features in it that they believe are also present in the Milky Way, but are made invisible by the Milky Way’s thick intervening clouds of dust. Astronomers study the Andromeda Galaxy’s spiral arms; the birth of stars, dense spherical groups of stars called globular clusters , as well as looser star groupings called open c...