Chaotic Comet Collisions around Star Suggest Presence of Unknown Planet

A puzzling build-up of carbon monoxide around the nearby star Beta Pictoris revealed to astronomers a stellar phenomenon: the splattered remains of comets colliding together around the star. The researchers believe they are observing this cosmic comet collision in real-time at a rate of one comet per five minutes, and that it may be caused by an unknown planet in orbit around the star.

The observations were made using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile, and the carbon monoxide (CO) gas swirling around Beta Pictoris acted as a "smoking gun" in the astronomers theories on what they were observing.

Bill Dent, a researcher at the Joint ALMA Office in Santiago, Chile, said that because molecules of CO can only survive for about 100 years before being destroyed by ultraviolet radiation, there must be a source that's continuously replenishing the CO.

Writing in the journal Science, Dent and his colleagues suggest the CO source is comets, which trap vast amounts of CO in their icy interiors as they blaze through space. When comets collide, as is common around young stars such as Beta Pictoris, they release their gassy contents into the stellar atmosphere.

However the high concentration of CO puzzled astronomers, because if the comets were colliding randomly the distribution of the CO gas would be equally random. Instead, it is concentrated in one area. Because of this, the astronomers theorize that a still-unknown planet is present in the Beta Pictoris system. Currently only one planet is known to orbit the star at a distance of about 750 million miles.

The gravity of this unseen planet may be shepherding the comets into one area around the star. A similar phenomenon is seen in our own solar system where Jupiter's mass keeps a group of asteroids in orbit around the Sun.

"To get the amount of CO we observed -- which is equal to about one-sixth the mass of Earth's oceans -- the rate of collisions would be truly startling, with the complete destruction of a large comet once every five minutes," said study co-author Aki Roberge, an astronomer at NASA's Goddard Space Flight Center in Greenbelt, Md. "To get this number of collisions, this would have to be a very tight, massive swarm."

"And carbon monoxide is just the beginning; there may be other more complex pre-organic molecules released from these icy bodies," Roberg added.

By continuing to study the system, the astronomers hope it will bring a better understanding of how our own solar system formed.