Check out the picture above. That's the Great Spiral Galaxy of Andromeda if the sky were bright enough. Isn't it just beautiful?

Unfortunately, the sky isn't that bright, but it's not the only image of this kind. Here's another one featured in NASA's Astronomy Picture of the Day:

Andromeda—or M31—is larger than our Milky Way. It is only 2.5 million light years from us. Pretty close but actually very far, considering a light year is 9.5 trillion kilometers.

M31 is on a direct collision course with our home galaxy. Our sky could one day look like the pictures above.

When it happens, star systems will lose their bearings, changing orbits all around. Our own solar system will "probably be tossed much farther from the galactic core than it is today."