Another galaxy smashed through the heart of the Cartwheel Galaxy 100 million years ago, and today the Cartwheel remains one of the most powerful UV-emitting galaxies near us, as that blue outer ring shows.

This false-color composite image consists of images from the Galaxy Evolution Explorer (blue), the Hubble Space Telescope (green), the Spitzer Space Telescope (red), and the Chandra X-ray Observatory (purple). The image was created in 2006, but NASA re-released it over the weekend, as part of a celebration of the International Year Of Astronomy 2009. [NASA]