It is not easy to be ringed. A newly released image from the James Webb Space Telescope, or JWST, shows the Cartwheel Galaxy still recovering from an encounter with a smaller galaxy 400 million years ago.
The Cartwheel Galaxy, named for its bright inner ring and colorful outer ring, lies about 500 million light-years from Earth. Astronomers think it used to be a large spiral like the Milky Way, until a smaller galaxy passed through it. In previous observations with other telescopes, the space between the rings seemed shrouded in dust.
Now, JWST infrared cameras have peered through the dust and found stars and structures never seen before (Serial Number: 7/11/22). The new image shows sites of intense star formation across the galaxy that were triggered by aftereffects of the collision. Some of those new stars are forming in spoke-like patterns between the central ring and the outer ring, a process that is not well understood.
Ring galaxies are rare, and galaxies with two rings are even more unusual. That odd shape means the long-ago collision created multiple ripples of gas that rippled back and forth in the galaxy left behind. It’s like dropping a stone into the bathtub, says JWST project scientist Klaus Pontoppidan of the Space Telescope Science Institute in Baltimore. “First you get this ring, then it hits the walls of your bathtub and it reflects, and you get a more complicated structure.”
The effect likely means the Cartwheel Galaxy has a long road to recovery ahead of it, and astronomers don’t know what it will look like in the end.
As for the smaller galaxy that caused all this chaos, it didn’t stick around to get its picture taken. “He has gone his merry way,” Pontoppidan says.