BBC: The first comet orbiting a star other than the Sun was found in 1987, and only three other such comets had been found since. But at the 221st American Astronomical Society meeting, the number of known exocomets nearly tripled with the announcement that seven more have been discovered. Brian Welsh and Sharon Montgomery of Clarion University used the McDonald Observatory in Texas to identify the comets based on the tiny changes in light reflected by the tails as the comets orbited their stars. Many comets are believed to come from debris clouds that orbit well away from parent stars. For the debris to leave the cloud and become a comet, it has to be pulled into an elliptical orbit by a planet or other large body. Because of that, the first exocomet led to the discovery of a planet orbiting the same star. Understanding the relationship between comets and planets and their parent stars will help astronomers better explain solar system formation and dynamics.