The true identity of centaurs is one of the enduring mysteries of astrophysics. Observations from NASA's Wide-field Infrared Survey Explorer (WISE) find most centaurs are comets.
Until now, astronomers were not certain whether centaurs are asteroids flung out from the inner solar system or comets travelling in toward the Sun from afar.
"Our data point to a cometary origin for most of the objects, suggesting they are coming from deeper out in the solar system," said James Bauer of NASA's Jet Propulsion Laboratory in Pasadena, California.
"Cometary origin" means an object likely is made from the same material as a comet, may have been an active comet in the past, and may be active again in the future, researchers said.
The findings come from the largest infrared survey to date of centaurs and their more distant cousins, called scattered disk objects. NEOWISE, the asteroid-hunting portion of the WISE mission, gathered infrared images of 52 centaurs and scattered disk objects.


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