What exactly are space centaurs? For years, researchers have been debating whether those mysterious celestial bodies, which orbit the sun between the orbits of Jupiter and Neptune, are asteroids or comets.
But new observations from NASA's Wide-field Infrared Survey Explorer (WISE) suggest that most centaurs are comets.
"Our data point to a cometary origin for most of the objects, suggesting they are coming from deeper out in the solar system," study author Dr. James Bauer, a planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a written statement. "Just like the mythical creatures, the centaur objects seem to have a double life."
Centaurs are named after that creature from Greek mythology whose head and torso are human but whose legs are those of a horse. Similarly, centaurs in space have a dual nature -- with characteristics similar to both asteroids zooming out from the inner solar system and comets traveling in toward the sun. But after studying the observations of 52 centaurs in space, researchers have found a predominance of comet-like characteristics.
Such as? "Comets have a dark, soot-like coating on their icy surfaces, making them darker than most asteroids," study co-author Dr. Tommy Grav, research scientist at the Planetary Science Institute in Tucson, Az., said in the statement. "Comet surfaces tend to be more like charcoal, while asteroids are usually shinier like the moon."
The study results indicate that roughly two-thirds of the centaur population are comets. It remains unclear whether the rest are asteroids.
The new research was published online on July 22, 2013 in Astrophysical Journal.