March 7, 2014
Massive Ring Of Carbon Monoxide Discovered In Turbulent Comet Field
[ Watch the Video: Colliding Comets Hint At Unseen Exoplanet ]
Brett Smith for redOrbit.com - Your Universe Online
NASA scientists have found evidence of a highly-turbulent comet field circling a star 63 light years from Earth. This cosmic shooting gallery has produced a massive ring of carbon monoxide gas and dust that also encircles the star, according to a new report published in the journal Science.
According to the report authors, the comet field is probably the result of either two icy worlds the size of Mars crashing together or frozen debris trapped by a currently-undiscovered planet.
"Although toxic to us, carbon monoxide is one of many gases found in comets and other icy bodies," said study author Aki Roberge, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md. "In the rough-and-tumble environment around a young star, these objects frequently collide and generate fragments that release dust, icy grains and stored gases."
Detected by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, this cloud of dust envelops Beta Pictoris, a bright star thought to be about 20 million years old. The ALMA images show the huge belt is mostly gathered in a single clump located about 8 billion miles from the star, or virtually three times the gap between the planet Neptune and the sun. The overall quantity of carbon monoxide detected is greater than 200 million billion tons, similar to about one-sixth the mass of Earth’s oceans, the study team said.
Because ultraviolet starlight splits up carbon monoxide molecules in about a century, the researchers said the ringed cloud may not be what it first seems.
“So unless we are observing Beta Pictoris at a very unusual time, then the carbon monoxide we observed must be continuously replenished," said study author Bill Dent, a researcher at the Joint ALMA Office in Santiago, Chile.
Dent and his team found that to counterbalance the breakdown of carbon monoxide molecules around Beta Pictoris, a large comet needs to be completely destroyed every five minutes. Only an unusually substantial and compressed swarm of comets could support such a high collision rate.
Because we see the disk virtually edge-on from our vantage point here on Earth, the ALMA information cannot establish if the carbon monoxide belt has a solitary concentration of gas or two concentrations on opposite sides of the star. The study team said they currently believe a two-clump scenario is more likely.
Similar to the way Jupiter's gravity has trapped a large number of asteroids in two groups in our own solar system, a giant planet located in the exterior of the Beta Pictoris system could bunch comets into a pair of tight, enormous swarms.
"Detailed dynamical studies are now under way, but at the moment we think this shepherding planet would be around Saturn's mass and positioned near the inner edge of the CO belt," said study author Mark Wyatt, an astronomer at the University of Cambridge in England.
Astronomers have already discovered one giant planet in the system orbiting close to the star, Beta Pictoris b, which has a mass several times greater than Jupiter. The study team theorized that another planet could have established near the star and transferred outward as the planetary disk went through modifications.
"We think the Beta Pictoris comet swarms formed when the hypothetical planet migrated outward, sweeping icy bodies into resonant orbits," Wyatt said.
If later observations show a single clump of dust and gas, the study team said a collision of two planets is a more likely cause.