The Andromeda Galaxy.

Andromeda Galaxy The Andromeda galaxy is the closest full size galaxy to the Milky Way because of this it is known as our nearest galactic neighbor. The Andromeda Galaxy is also the only galaxy visible to the naked eye in the Northern Hemisphere. At 2.9 million light-years from Earth, Andromeda is also the farthest object that can be seen from Earth. Andromeda is not only known as our closest neighbor but scientists also refer to Andromeda …

…least possible. Such a civilization, millions of years more mature than our own, would probably be the explorers' best chance of ever seeing their native earth again. We may have no idea of how to cross the gulf between the galaxies with magical speed, but our Andromedan neighbors might have solved the problem eons ago. In fact, statistically the Andromedans are more likely to show up in our solar system than we are in theirs.