A Puzzling Object No Longer Thought To Be A Comet

A puzzling object that seemed to be a comet flying inside the solar system’s asteroid belt is no comet at all, but the remains of a violent collision between two fossil rocks that populate the belt, astronomers say.

The object was first sighted in early January by astronomers at the Air Force LINEAR project telescope in New Mexico, who reported it as a comet that must have flown into the asteroid belt from the solar system’s outer reaches, as all comets do. It was the fifth presumed comet to be reported in the unlikely region, they said, and they gave it the code name P/2010 A2.

The main asteroid belt lies between the orbits of Mars and Jupiter, and the strange object was spotted there again later in the month by astronomers at the Kitt Peak National Observatory in Tucson.

David Jewitt, a leading expert on comets and asteroids at UCLA, was intrigued by the reports of a possible comet inside the asteroid belt where millions of rocky objects fly in orbit around the sun, constantly colliding and grinding each other down.

He quickly obtained time for the Hubble Space Telescope’s wide field camera to home in on the object, and the images showed a stony nucleus just beyond an X-shaped halo of rocky filaments and a long, streaming tail of dust and gravel.

“Its appearance is very, very strange,” Jewitt said in an interview. “Strictly speaking it’s a hybrid – a comet because of its tail, but with no gas in the tail, it has to be a crash between two small asteroids, and we’re seeing it as it happened.”

The collision – which probably happened only a few weeks ago – reduced both bodies to a cluster of smashed-up rocks and gravel that under the radiation pressure of sunlight streamed out into a long, long tail looking just like a comet’s, Jewitt said.

Weird Comet Or Asteroid?

The mystery object, located 100 million miles from Earth, may really be the aftermath of a hypervelocity collision between two asteroids — like a bullet hitting another bullet. Whatever it is, nothing quite like it has ever before been seen in the heavens. The comet-like object, called P/2010 A2, was first discovered by the LINEAR (Lincoln Near-Earth Asteroid Research program) sky survey on January 6. Telescopes around the world turned their attention to it. Comet expert David Jewitt of UCLA quickly applied for special discretionary time on the Hubble Space Telescope to get a close-up look at the object. Hubble pictures taken on January 25 and 29 left everyone speechless. It’s fun watching the expression on the faces of astronomers when they first see it, like “WTF!?”

It’s so weird-looking that you want to call the UFO hotline. Maybe it’s a Romulan “Bird of Prey” starship decloaking as it enters our solar system.