Fun Fact: Did You Know that the Andromeda Galaxy and the Milky Way Galaxy have already started merging?
There is one part of a galaxy called the Halo. The Halo is a cloud of gas and dust that reaches out thousands of light-years from the galaxy. The Milky Way’s Halo and the Andromeda Galaxy’s Halo have already started colliding. But the galaxies won’t start colliding until around four billion years from now. Some examples of two colliding galaxies is the Whirlpool Galaxy and the Mice Galaxies.