Every six seconds, for millions of years, comets have been colliding with one another near a star in the constellation Cetus called 49 CETI, which is visible to the naked eye.
Over the past three decades, astronomers have discovered hundreds of dusty disks around stars, but only two — 49 CETI is one — have been found that also have large amounts of gas orbiting them.
Young stars, about a million years old, have a disk of both dust and gas orbiting them, but the gas tends to dissipate within a few million years and almost always within about 10 million years. Yet 49 CETI, which is thought to be considerably older, is still being orbited by a tremendous quantity of gas in the form of carbon monoxide molecules, long after that gas should have dissipated.
"We now believe that 49 CETI is 40 million years old, and the mystery is how in the world can there be this much gas around an otherwise ordinary star that is this old," said Benjamin Zuckerman, a UCLA professor of physics and astronomy and co-author of the research, which was recently published in the Astrophysical Journal. "This is the oldest star we know of with so much gas."
Zuckerman and his co-author Inseok Song, a University of Georgia assistant professor of physics and astronomy, propose that the mysterious gas comes from a very massive disk-shaped region around 49 CETI that is similar to the sun's Kuiper Belt, which lies beyond the orbit of Neptune.
The total mass of the various objects that make up the Kuiper Belt, including the dwarf planet Pluto, is about one-tenth the mass of the Earth. But back when the Earth was forming, astronomers say, the Kuiper Belt likely had a mass that was approximately 40 times larger than the Earth's; most of that initial mass has been lost in the last 4.5 billion years.
By contrast, the Kuiper Belt analogue that orbits around 49 CETI now has a mass of about 400 Earth masses — 4,000 times the current mass of the Kuiper Belt.
"Hundreds of trillions of comets orbit around 49 CETI and one other star whose age is about 30 million years. Imagine so many trillions of comets, each the size of the UCLA campus — approximately 1 mile in diameter — orbiting around 49 CETI and bashing into one another," Zuckerman said. "These young comets likely contain more carbon monoxide than typical comets in our solar system. When they collide, the carbon monoxide escapes as a gas. The gas seen around these two stars is the result of the incredible number of collisions among these comets.
"We calculate that comets collide around these two stars about every six seconds," he said. "I was absolutely amazed when we calculated this rapid rate. I would not have dreamt it in a million years. We think these collisions have been occurring for 10 million years or so."
Using a radio telescope in the Sierra Nevada mountains of southern Spain in 1995, Zuckerman and two colleagues discovered the gas that orbits 49 CETI, but the origin of the gas had remained unexplained for 17 years, until now.
University of California - Los Angeles: http://www.newsroom.ucla.edu
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
And made this stunning picture
A star-studded group of campaigners are promoting Asteroid Day to raise awareness of the threat of incoming rocks. Are we really facing imminent disaster?
An unmanned Vega rocket blasted off from French Guiana on Monday to put a sophisticated Earth-watching satellite into orbit, a European Space Agency webcast showed.
"It looks like we can finally include Venus in the small club of volcanically active solar system bodies," said an ESA scientist
A Canadian company put an HD camera on the ISS and got video so clear you can see cars driving past Boston's Fenway Park
Information it gathered is helping to improve climate models
Spacecraft to come within 180km of comet’s surface in attempt to improve contact signal and allow commands to be sent to the newly awakened lander
Housed under a dome located 8,000 feet above ground in a dormant Hawaii volcano
The ice world Tethys has had a very hard life, as a new image from the Cassini spacecraft shows.
Amazing what interns can do besides fetch coffee and make trips to the mail room