400 million light-years
The unusual shape of the Cartwheel galaxy results from one of the smaller galaxies to the left passing through it about 100 million years ago. This created a huge compression wave, like a ripple in a pond, and this wave triggers intense bouts of star formation. Four of NASA's orbiting observatories collaborated to make this image: the Chandra X-ray Observatory (purple), GALEX in ultraviolet (blue), the Hubble Space Telescope (green) and the infrared Spitzer Space Telescope (red).
Credit: Composite image made by P. Appleton et al. for NASA / JPL-Caltech / ESA.
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