Answer: Andromeda Galaxy

Space is a vast and lonely place, so it should not come as a surprise that our nearest major galactic neighbor is far, far, away. How far? Our nearest neighbor, Andromeda, is approximately 2.5 million light years from Earth and the space between the Milky Way and Andromeda is populated with only a smattering of small galaxies, known as satellite galaxies. In terms of scale, using Earth as a point of reference, these satellite galaxies are like small islands and the major galaxies are like continents.

While Andromeda is so far away it would be unreasonable to reach it using current technology (even if we sent a probe, it would take longer than the span of all of human civilization to get there), eventually, even though we won’t be around to see it, Earth will pay a visit. The Milky Way and Andromeda are on a very slow collision course and in roughly 4.5 billion years, our two galaxies will merge together into an elliptical or disc-shaped galaxy astronomers have nicknamed Milkomeda or Milkdromeda.