Our home galaxy, the Milky Way, is one of the leading members of the Local Group, a collection of at least 80 galaxies bound together by their mutual gravitational pull. The Andromeda Galaxy, M31, is the largest member of the group, with the Milky Way a close second. Roughly three dozen members of the Local Group orbit the Milky Way. The entire group spans about 10 million light-years. [Richard Powell/Wikipedia]