Comet Swarm Smash-Up Spied Around Nearby Star
Illustration of colliding comets around Beta Pictoris.
A giant clump of carbon monoxide found around a nearby star hints at collisions between comets and the presence of a massive hidden planet, according to recent observations with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile.
Located a little over 63 light-years away in the southern constellation Pictor, Beta Pictoris is a young star slightly more massive and about 9 times brighter than the sun. It’s surrounded by a dusty protoplanetary disk that we see edge-on and orbited by at least one known planet — Beta Pictoris b.
ALMA observations of CO clumps around Beta Pictoris.
ALMA (ESO/NAOJ/NRAO) and NASA’s Goddard Space Flight Center/F. Reddy
Based on the behavior of an enormous ring of dust and carbon monoxide (CO) gas surrounding Beta Pictoris three times as far out as Neptune is from our sun, either multiple small, rocky planets were once present and have recently smashed into each other or, considered more likely, millions of icy comets have been gravitationally gathered into a condensed cluster by a single, massive planet and there they are currently on chaotic collision courses.
The collisions are thought to replenish the carbon monoxide in the ring, which would otherwise be quickly broken down by UV light from the star — within about a century.
“To produce the amount of gas we detect, we’re looking at the equivalent of the total destruction of a large comet every five minutes,” said Aki Roberge, an astronomer at NASA’s Goddard Space Flight Center and coauthor on the paper. ”To get this number of collisions, this would have to be a very tight, massive swarm.”
The swarm could be focused by the gravity of an as-yet undiscovered planet orbiting closer in to Beta Pictoris.
“A planet with roughly Saturn’s mass could do the job,” said Roberge.
If the comet collisions were occurring randomly throughout the entire disk, the gas observed would be evenly distributed and not in specific dense regions.
Whether there are multiple clumps of gas around Beta Pictoris or just one is still unknown — because we see the entire system edge-on it’s difficult to determine. The motion of the densest, brightest clump appears to indicate two, though.
Regardless of whether the CO source is colliding comets or planets — or a combination of both — astronomers are “optimistic that there are many more planets waiting to be found around Beta Pictoris,” according to a news article from the National Radio Astronomy Observatory.(Mar 7, 2014 11:12 AM ET // by Jason Major)
