Hubble observes cosmic 'bulls-eye' galaxy

The Hubble telescope has captured an image of a distant galaxy that was a target bulls-eye in a cosmic collision with another galaxy, European astronomers say. The image of galaxy NGC 922 reveals not a normal spiral galaxy but one whose arms are disrupted, with a stream of stars extending outward and a bright ring of nebulae encircling the core, a release from the European Space Agency's Paris headquarters reported Thursday. Those features are the evidence of a cosmic bulls-eye millions of years ago when a smaller galaxy smashed through the center of NGC 922 and sailed out the other side, astronomers said. The collision created ripples that disrupted the clouds of gas in NGC 922, triggering the formation of new stars whose radiation then lit up the remaining gas creating the bright pink color seen in the space telescope image, they said. This process of excitation and emission of light by gases is similar to what happens in neon signs, astronomers said. Objects like NGC 922, dubbed collisional ring galaxies, are relatively rare in our cosmic neighborhood, they said. While galaxy collisions and mergers are commonplace, the precise alignment and ratio of the colliding galaxies' sizes needed to create a ring such as the one seen in NGC 922 is unusual, they said.