Caption On the left is a composite image of the Triangulum galaxy, made by overlaying individual images taken by the Hubble Space Telescope as part of the PHATTER survey. Distributions of old and ...

The spiral galaxy Messier 33 (M33), also known as the Triangulum Galaxy, is the third-largest member of the Local Group of galaxies, after the Andromeda galaxy (M31) and our own Milky Way.