NASA's Wide-field Infrared Survey Explorer, or WISE, has discovered its first comet, one of many the mission is expected to find among millions of other objects during its ongoing survey of the whole sky in infrared light. Officially named "P/2010 B2 (WISE)," but known simply as WISE, the comet is a dusty mass of ice more than 2 kilometers (1.2 miles) in diameter. It probably formed around the same time as our solar system, about 4.5 billion years ago. Comet WISE started out in the cold, dark reaches of our solar system, but after a long history of getting knocked around by the gravitational forces of Jupiter, it settled into an orbit much closer to the sun. Right now, the comet is heading away from the sun and is about 175 million kilometers (109 million miles) from Earth.


The WISE telescope, which launched into a polar orbit around Earth on December 14, 2009, is expected to discover anywhere from a few to dozens of new comets, in addition to hundreds of thousands of asteroids. Comets are harder to find than asteroids because they are much more rare in the inner solar system. Whereas asteroids tour around in the "main belt" between the orbits of Mars and Jupiter, large numbers of comets orbit farther away, in the icy outer reaches of our solar system. Both asteroids and comets can fall into orbits that bring them close to Earth's path around the sun. Most of these "near-Earth objects" are asteroids but some are comets. WISE is expected to find new near-Earth comets, and this will give us a better idea of how threatening they might be to Earth.