The Cartwheel Galaxy

A  spectacular collision between two galaxies appears, located 500 million light-years away in the constellation Sculptor. This is known as the Cartwheel Galaxy shown in the photo from NASA below.

 

The striking ring-like object is a result of a small intruder galaxy -- possibly one of two objects to the right of the ring -- that careened through the core of the host galaxy. As if you tossed a stone in a river,  the collision sent a ripple of energy into space, pushing gas and dust in front of it. Expanding at 200,000 miles per hour, this cosmic event leaves in its wake a firestorm of new star creation. The bright blue knots that are gigantic clusters of newborn stars and immense loops and bubbles blown into space by exploding stars.

The Cartwheel Galaxy presumably was a normal spiral galaxy like our Milky Way before the collision. This spiral structure is beginning to re-emerge, as seen in the faint arms or spokes between the outer ring and bulls-eye shaped nucleus. The ring contains at least several billion new stars that would not normally have been created in such a short time span under normal conditions.