Messier 103 (also known as M103, or NGC 581) is an open cluster where a few hundred, mainly very faint, stars figure in Cassiopeia.[a] It was discovered in 1781 by Charles Messier's friend and collaborator Pierre Méchain. It is located between 8,000 to 9,500 light-years from the Solar System and ranging over about 15 light years. It holds about 40 certain-member stars, two of which have magnitudes 10.5, and a 10.8 red giant, which is the brightest within the cluster. A bright known foreground object is the star Struve 131, not a member of the cluster. The cluster may have 172 stars if including those down to 50% probability of a gravitational tie. M103 is about 22 million years old.