... Where did these two irregular moons of Uranus originate? Last week two previously undiscovered moons of the distant gas planet were confirmed, the first in irregular orbits. ... M31: The Andromeda Galaxy . ... Andromeda is the nearest major galaxy to our own Milky Way Galaxy. ... When two galaxies collide, however, the stars that compose them usually do not. This is because galaxies are mostly empty space and, however bright, stars only take up only a small amount of that space. ...