Discovered by Pierre Méchain in 1781 or 82.
Messier 108, also known as NGC 3556, is a barred spiral galaxy in the constellation Ursa Major. The galaxy is seen close to edge on with an inclination of approximately 75 degrees. The galaxy is a member of the Ursa Major Cluster of galaxies and is part of the Virgo Supercluster of galaxies. The galaxy is classified as type SBbc which equates to a barred spiral with loosely wound arms. The galaxy is approximately 45 million light-years from the Earth. Our edge on view of M108 is dominated by dense dust clouds. The supermassive black hole at the core of the galaxy has an estimated mass of 24 million times that of our Sun.