Centaurs are small celestial bodies found between the orbits of Jupiter and Neptune. Their true nature has been a great mystery to astrophysicists, but NASA’s WISE may finally have determined that they are comets.
The true nature of centaurs have long been a puzzle to astronomers. The debate has largely centered around whether they are comets traveling towards the sun from afar, or asteroids that have been flung out of the inner solar system. NASA has deployed its Wide-field Infrared Survey Explorer (WISE) to investigate the objects and the conclusion is that the objects originate from comets. “Just like the mythical creatures, the centaur objects seem to have a double life,” said James Bauer from NASA’s Jet Propulsion Laboratory, “Our data point to a cometary origin for most of the objects, suggesting they are coming from deeper out in the solar system.”
The study of the objects was the most comprehensive analysis of centaurs and their more distant cousins, scattered disk objects, to date. NEOWISE, the asteroid hunting part of WISE, analyzed 52 objects, whereof 15 were new discoveries. The NASA scientists were able to distinguish the objects as comets by looking at their color. A reddish hue usually indicates an asteroid. Meanwhile, since comets usually have a soot-like covering to their icy bodies, they will appear darker. Tommy Grav, co-author of the study from the Planetary Science Institute in Arizona, explains: “Comet surfaces tend to be more like charcoal, while asteroids are usually shinier like the moon.”
Roughly two-thirds of the centaurs seem to be comets, while the rest may have come from our asteroid field. Regardless, the centaurs won’t remain in their orbits forever: Their orbits are unstable and ultimately, the gravitational effects of the gas giants will either fling them deeper into space or closer to the sun. In fact, some of the centaurs may one day return to being comets.