The first recorded observation of Andromeda was in the year 905 by a Persian astronomer. Charles Messier created the Catalogue of Nebulae and Star Clusters (1771-1784) and entered the object as the 31st item. The name M31 is referred to as the object's Messier number in which the M is followed by his catalogue number. He theorized the object was a nebula (cloud of gas and dust) and it wasn't until 1923 that American astronomer Edwin Hubble measured the distance to M31 and showed that it was a distant galaxy.
This is the coolest fact. The spiral galaxy of Andromeda is the furthest object in the universe that can be seen with the naked eye. It is 2.5 million light-years from Earth (light travels at 186,000 miles per second). Andromeda is believed to have between 300 billion and 400 billion Suns. It's diameter of about 200,000 light-years makes it appear five times larger than the full Moon in our sky.
Andromeda and the Milky Way are moving toward each other at about 75 miles per second. The two galaxies will eventually collide and form a single, giant elliptical galaxy. The process will start in about 2 billion years and completely merge by about 5 billion years from now. The black holes at the center of the two galaxies will combine to form a single, supermassive black hole potentially forming a quasar. Computer models suggest that our Sun and solar system will survive but will likely be thrown into the distant outer halo of the new combined galaxy.
Now you’re a little smarter, Girlfriend — And so am I.