Closest spiral galaxy to our Milky Way galaxy is Andromeda and even traveling at the speed of light it would take 2 million years to reach it. Andromeda Galaxy, Milky Way, the Triangulum Galaxy, and about 30 smaller galaxies belong to a group called Local Group. There are 100 billion galaxies that we can observe. Prediction is that there is much more, but Hubble Space Telescope couldn't detect them. The Andromeda Galaxy and the Milky Way is predicted to merge within the next 5 billion years. In the event like this smaller galaxies are consumed by larger ones. Andromeda galaxy is twice as large as Milky Way.