NGC 4651: The Umbrella Galaxy

Explanation: Spiral galaxy NGC 4651 is a mere 35 million light-years distant, toward the well-groomed constellation Coma Berenices . About 50 thousand light-years across, this galaxy is seen to have a faint umbrella-shaped structure (right) that seems to extend some 50 thousand light-years farther, beyond the bright galactic disk. The giant cosmic umbrella is now known to be composed of tidal star streams . The streams themselves are extensive trails of stars gravitationally stripped from a smaller satellite galaxy that was eventually torn apart. Placing your cursor over the image will superimpose a simulation of the satellite galaxy's path as it was disrupted and absorbed into NGC 4651. Recent work by a remarkable collaboration of amateur and professional astronomers to image faint structures around bright galaxies suggests that even in nearby galaxies , such tidal star streams are common. The result is predicted by models of galaxy formation, including the formation of our Milky Way.