Astronomers have found a debris disk around a sun-like star that may be forming or has formed its terrestrial planets. The disk -- a probable analog to our asteroid belt -- may have begun a solar-system-scale demolition derby, where the rocky remains of failed planets collide chaotically. "This is one of a very rare class of objects that may give us a glimpse into what our solar system may have looked like during the formation of our terrestrial planets," said Dean C. Hines of the Space Science Institute, a leader of the team that discovered the rare objects with NASA's...