The Cartwheel Galaxy

A rare and spectacular head-on collision between two galaxies appears in this Hubble Space Telescope image of the Cartwheel Galaxy, located 500 million light-years away in the constellation Sculptor. The striking ring-like feature is a direct result of a smaller intruder galaxy — possibly one of two objects to the right of the ring — that careened through the core of the host galaxy. Like a rock tossed into a lake, the collision sent a ripple of energy into space, plowing gas and dust in front of it. Expanding at 200,000 miles per hour, this cosmic tsunami left in its wake a firestorm of new star creation.