M31, the Andromeda Galaxy, is the nearest giant galaxy to the Milky Way, just 2.5 million light-years away. Its size and mass are similar to the Milky Way's. It's orbited by dozens of smaller galaxies, the largest of which is M110, which looks like a small, bright blob close to the lower right of M31's center. Charles Messier discovered the smaller galaxy 250 years ago. M110 is a dwarf elliptical galaxy. It's only a fraction of the size and mass of M31. It doesn’t have spiral arms or other obvious structures, just a bright center with stars fading away toward the edges. [Torben Hansen/Wikipedia]
Find out more in our radio program entitled Messier 110.