NASA’s WISE Shows That Most of Celestial Centaurs are Comets

For years, centaurs have been one of the enduring mysteries of astrophysics. A new study by NASA shows that centaurs are comets and not asteroids.

 New observations made by NASA's Wide-field Infrared Survey Explorer (WISE) shows that most centaurs - the small celestial bodies that are orbiting between Jupiter and Neptune - are comets.

Previously, astronomers weren't sure about the identity of centaurs. According to some, they were asteroids from the inner solar system while others believed the centaurs to be comets that were moving towards the Sun. 

But NASA's WISE has put an end this mystery stating that these small celestial bodies called centaurs are actually comets.

"Just like the mythical creatures, the centaur objects seem to have a double life," said James Bauer of NASA's Jet Propulsion Laboratory in Pasadena, Calif., in a press statement. "Our data point to a cometary origin for most of the objects, suggesting they are coming from deeper out in the solar system."

Bauer who is also a lead author of a paper said that, by 'cometary origin' we mean that an object is likely made from the same materials as that of a comet. Centaurs may have been active comets in the past and may regain activity in the future.

NASA was able to solve this mystery with the help of NEOWISE - the asteroid hunting part of WISE mission. It captured infrared images of 52 centaurs and scattered disk objects that are the distant cousins of centaurs. Out of the 52 centaurs, 15 were new discoveries.  Both centaurs and scattered disk objects orbit in an unstable belt. The fate of these cetuars is decided by the gravity of nearby planets that will throw them either closer to the sun or far from their current location.

The researchers used NEOWISE to determine the reflectivity of the centaur. By incorporating the previous studies made on the color of these objects, the researchers were able to conclude that the small celestial objects were comets.  Visible-light observations have shown that centaurs are generally either blue-gray or reddish in shade. But the reflectivity data from NEOWISE confirmed that the most of the blue gray objects were dark indicating they were comets, reports IB Times.

"Comets have a dark, soot-like coating on their icy surfaces, making them darker than most asteroids," said the study's co-author, Tommy Grav of the Planetary Science Institute in Tucson, Ariz. "Comet surfaces tend to be more like charcoal, while asteroids are usually shinier like the moon."

According to study results, about two-thirds of the centaur population are comets. Researchers aren't certain about the origins of other centaurs.

The study was published in the Astrophysical Journal.