All sorts of weird stuff can happen when two galaxies collide into one-another. Sometimes they form weird cosmic eyes, sometimes they form something that just looks like a blob. Hubble captured another result: a giant galactic wagon wheel.
About 400 million light-years away and 200 million years ago, a small galaxy collided with the center of the larger spiral Cartwheel galaxy, sending out waves a bit like the ones made by dropping a rock in a pond, and formed a ring galaxy. That outer ring is about 150,000 light-years in diameter — that’s one and a half times the size of the Milky Way.
Thanks to the violent crash, shockwaves of gas and dust created the Cartwheel galaxy’s outer ring, which is a hotbed for rapid star formation. The blue of the ring comes from all the bright, young stars. The spokes are remnants of the galaxy’s original shape, and it appears the galaxy is trying to reform.
The Cartwheel galaxy is a member of a cluster of galaxies in the constellation Sculptor. Astronomers aren’t quite sure what happened to the galaxy responsible for the collision, but one of the two galaxies to the left of the Cartwheel might be the culprit. Radio waves from a hydrogen tail on another galaxy, not pictured, suggest there’s a third suspect on the run about 250,000 light years from the Cartwheel galaxy. Even if astronomers don’t solve the case, at least the aftermath is great to look at.