Located 2.5 million light years from the Milky Way, the Andromeda galaxy is the largest galaxy in the Local Group. Also categorized as M31, Andromeda is a spiral galaxy roughly 220,000 light years in diameter, containing approximately 1 trillion stars (compared to the Milky Way's 300 billion). The Heleus cluster is a large star cluster located on the galaxy's outer fringe.
Andromeda has roughly 14 satellite galaxies, which orbit the galactic disk. Evidence shows a disturbance where one of these companion galaxies, M32, passed through Andromeda's spiral arms several million years ago. Andromeda itself is also accelerating towards the Milky Way at roughly 100km/s. In roughly 4 billion years, the Andromeda and Milky Way galaxies will collide and merge, forming a new galactic disk.