M31 - The Andromeda Galaxy

Credits: Keith Turnecliff, Long Itchington

This image of our nearest major galactic neighbour, M31, is the largest Hubble mosaic to date. The 1.5 billion pixels in the mosaic reveal over 100 million stars and thousands of star clusters embedded in a section of the pancake-shaped disk of M31, also known as the Andromeda galaxy. Though the galaxy is over 2 million light-years away, Hubble is powerful enough to resolve individual stars in this 61,000-light-year-long stretch of the disk. It’s like photographing a beach and resolving individual grains of sand.

Facts about M31 by Keith Turnecliff

M31 is located in the constellation Andromeda and is best observed in November. Boasting an apparent magnitude of 3.1, the galaxy can be seen with the naked eye, even in areas with moderate light pollution. Because it is such an easily observed feature in the night sky, it is impossible to say who discovered the Andromeda galaxy.
However, Persian astronomer Abd al-rahman al-Sufi’s The Book of Fixed Stars from the year 964 contains the first known report of the object.