NASA’s WISE Reveals Mysterious Centaurs are Mostly Comets

Scientists are still puzzled about the mysterious nature of the centaurs, or the sub-planetary bodies, that are orbiting the Sun between the planets Jupiter and Neptune.

The true nature of the centaurs - whether they are asteroids or comets - has been the subject of thousands of scientific debates. Actually, the term "centaur" was coined by scientists to refer to these celestial bodies because of their dual nature, similar to the centaur in the Greek mythology.

Despite thousands to millions of studies focused on centaurs, scientists are still undecided whether centaurs are asteroids that "flung out from the inner solar system" or comets that travelled toward the Sun. This is why the identity of centaurs is considered as one of the biggest mysteries of astrophysics.

But a new study based on data collected by NASA revealed that most of these celestial bodies are actually comets. The findings were revealed through a study published in the Astrophysical Journal, which used the observation from NASA's Wide-field Infrared Survey Explorer (WISE).

"Just like the mythical creatures, the centaur objects seem to have a double life. 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 the paper published in the Astrophysical Journal.

NASA explained that the term "cometary origin" means that an object is most likely made of materials found in a comet. It could also mean that the celestial body may have been a comet in the past that could be a comet again in the future.

The asteroid-hunting part of the WISE mission, called NEOWISE, captured infrared images of 52 centaurs, including scattered disk objects that are considered the distant cousins of centaurs.

The infrared data gave scientists information on the albedos, or reflectivity, of the objects. It helped scientists determine the colors of the objects, which led to their observation that the blue-gray centaurs are mostly dark, which is a "telltale sign" of a comet.

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

But while scientists were able to make significant developments in their study, NASA said that future NEOWISE research will still reveal the secrets of the mysterious centaur further.