What Happens to Earth When the Milky Way and Andromeda Galaxies Collide?
We already know that the Milky Way and Andromeda galaxies are headed for a catastrophic collision, in which they spend billions of years pulling at each other until they've violently merged. And miraculously enough, Earth will actually survive this whole brutal process. But our planet will still be caught in the middle of this collision, and its view of the universe will never be the same.
The two galaxies are set for a head-on collision with each other in 3.75 billion years, and then the merger will last for another six billion years. So to be more accurate, Earth would have survived the merger, except that the Sun is expected to consume the Earth in five billion years, so we'll have to miss the end of the show. Here's a time lapse of the entire process from the perspective of a distant observer:
Our solar system will be somewhat affected by this, as the Sun will likely be pulled into a new orbit, and all of its planets will come along for the ride, but it is unlikely that anything too significant would happen to Earth, such as a collision with another star.
"The reason we think that our solar system will not be much affected by this collision... is that galaxies are mostly empty space," said Roeland van der Marel of the Space Telescope Science Institute. "Even though our galaxy, as well as the Andromeda galaxy, has 100 billion stars in it, they're very far apart. If two galaxies actually collide with each other the stars basically pass right between each other, and the chance of two stars directly hitting each other is really, really small."
Here is our current Earthly view of the Milky Way, with no Andromeda to be found, as it is currently 2.5 million light years from Earth:
But in 3.75 billion years, the galaxies will be ready to begin merging:
As the galaxies move closer and closer to each other, their respective gravitational pulls will warp the other until the formerly separate galaxies make the night sky look like a smudged painting:
Then, after doing this destructive dance for billions of years, the supermassive black holes in the center of each galaxy will merge, and the Milky Way and Andromeda galaxies will have merged into one elliptical galaxy. And although Earth will likely not be there to see it, here is what the night sky would look like at the end of the process:
And here's another video depicting the collision, just for good measure: