Comet-Like Asteroid Boasts Dusty Tail

In a case of mistaken identity, a newly active asteroid in our solar system's famous Main Belt is boasting a dusty tail, thinking it's more a comet than an asteroid, according to recent research.

Usually it's easy to tell the difference between a comet and an asteroid. A comet is a body composed of rock and ice that, when it passes close to the Sun, heats up and begins to sublimate, displaying a visible tail or coma. Asteroids, on the other hand, are composed mostly of rock and typically have few comet-like qualities.

But in recent years several asteroids have broken the boundaries of their definition and begun to sport dusty tails. A dozen of such unusual asteroids in the main asteroid belt have been identified thus far, and now a long-known asteroid is joining the club.

Called 62412, it's the first comet-like object seen in the Hygiea family of asteroids, and only the 13th known active asteroid in the main asteroid belt, located between Mars and Jupiter. Active asteroids, unlike others of their kind, sometimes sport a tail when dust and gas is ejected from their surface, giving them a comet-like appearance.

The Carnegie Institution's Scott Sheppard and Chadwick Trujillo of the Gemini Observatory just recently discovered an unexpected tail on 62412, an object which had for the last 10 years been considered a typical asteroid.

"Until about ten years ago, it was pretty obvious what a comet was and what a comet wasn't, but that is all changing as we realize that not all of these objects show activity all of the time," Sheppard said in a statement.

Sheppard and Trujillo learned from their observations that 62412 has a very fast rotation that likely shifts material around its surface, some of which may be emitted to form the comet-like appearance. This tail of dust is most likely created from ejected material off its surface, or from ice within the asteroid subliming into water vapor after being exposed to the surface.

The duo plans to continue monitoring 62412, and hope to better understand the processes that cause some asteroids to become active.

They presented their findings Nov. 11 at the American Astronomical Society's Division of Planetary Sciences meeting.