Subscribe free to our newsletters via your
. 24/7 Space News .




EXO WORLDS
Exocomets may be as common as exoplanets
by Robert Sanders for Berkeley News
Berkeley CA (SPX) Jan 09, 2013


Artistic depiction of dust and comets around the young star Beta Pictoris as seen from the outer edge of its disk. NASA image by Lynette Cook.

Comets trailing wispy tails across the night sky are a beautiful byproduct of our solar system's formation, icy leftovers from 4.6 billion years ago when the planets coalesced from rocky rubble.

The discovery by astronomers at the University of California, Berkeley, and Clarion University in Pennsylvania of six likely comets around distant stars suggests that comets - dubbed "exocomets" - are just as common in other stellar systems with planets.

Though only one of the 10 stars now thought to harbor comets is known to harbor planets, the fact that all these stars have massive surrounding disks of gas and dust - a signature of exoplanets - makes it highly likely they all do, said Barry Welsh, a research astronomer at UC Berkeley's Space Sciences Laboratory.

"This is sort of University of California, Berkeley
in current planetary formation studies," Welsh said. "We see dust disks - presumably the primordial planet-forming material - around a whole load of stars, and we see planets, but we don't see much of the stuff in between: the asteroid-like planetesimals and the comets. Now, I think we have nailed it. These exocomets are more common and easier to detect than people previously thought."

Welsh will present the findings on Monday, Jan. 7, during a meeting of the American Astronomical Society in Long Beach, Calif. Three of the new exocomets were reported in the Oct. 2012 issue of the journal Publications of the Astronomical Society of the Pacific by Welsh and colleague Sharon L. Montgomery of the Department of Physics at Clarion University.

Welsh also will participate in a media briefing on Tuesday, Jan. 8, at 2:30 p.m. PST in Room 204 on Level 2 of the Long Beach Convention Center.

Welsh summarized the current theory of planet formation as "interstellar dust under the influence of gravity becomes blobs, and the blobs grow into rocks, the rocks coalesce and become bigger things - planetesimals and comets - and finally, you get planets."

Many stars are known to be surrounded by disks of gas and dust, and one of the closest, beta-Pictoris (b-Pic), was reported to have comets in 1987. In 2009, astronomers found a large planet around B-Pic about 10 times larger than Jupiter. Three other stars - one discovered by Welsh in 1998 - were subsequently found to have comets.

"But then, people just lost interest. They decided that exocomets were a done deal, and everybody switched to the more exciting thing, exoplanets," Welsh said.

"But I came back to it last year and thought, 'Four exocomets is not all that many compared to the couple of thousand exoplanets known - perhaps I can improve on that.'"

Detecting comets may sound difficult - after all, the snowballs are typically only 5-20 kilometers (3-13 miles) in diameter.

But Welsh said that once comets are knocked out of their parking orbit in the outer reaches of a stellar system and fall toward a star, they heat up and evaporate. The evaporating comet, which is what we see with comets such as Halley and next year's highly anticipated Comet ISON, creates a brief, telltale absorption line in the spectrum of a star.

The six new exocomet systems were discovered during three five-night-long observing runs between May 2010 and November 2012 using the 2.1-meter telescope of the McDonald Observatory in Texas. The telescope's high resolution spectrograph revealed weak absorption features that were found to vary from night to night, an outcome that Welsh and Montgomery attributed to large clouds of gas emanating from the nuclei of comets as they neared their central stars.

All of the newly discovered exocomets - 49 Ceti (HD 9672), 5 Vulpeculae (HD 182919), 2 Andromedae, HD 21620, HD 42111 and HD 110411 - are around very young type A stars, which are about 5 million years old, because Welsh's detection technique works best with them.

With a higher resolution spectrograph, he might be able to detect comets around the older and yellower G and F stars around which most exoplanets have been found.

Nevertheless, all evidence suggests that these dusty A stars should have planets, and planets are the only thing that could knock a comet out of its orbit and make it fall toward its star.

"If it quacks, waddles and has feathers, then it's probably a duck," he said.

The work was supported by the National Aeronautics and Space Administration.

.


Related Links
University of California, Berkeley
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle








EXO WORLDS
Kepler Gets a Little Help From Its Friends
Pasadena CA (JPL) Jan 09, 2013
More than 2,300 exoplanet candidate discoveries have made it the most prolific planet hunter in history. But even NASA's Kepler mission needs a little help from its friends. Enter the Kepler follow-up observation program, a consortium of astronomers dedicated to getting in-depth with the mission's findings and verifying them to an extremely high degree of confidence. A single Kepler observ ... read more


EXO WORLDS
Mission would drag asteroid to the moon

Russia designs manned lunar spacecraft

GRAIL Lunar Impact Site Named for Astronaut Sally Ride

NASA probes crash into the moon

EXO WORLDS
Lockheed Martin Delivered Core Structure For First GOES-R Satellite

Opportunity Scores Another Dust Cleaning Event At Vermillion

Curiosity Rover Explores Yellowknife Bay

'Black Beauty' could yield Martian secrets

EXO WORLDS
2012 in Polish space activities

Captain's log: real space chat for Star Trek crew

Congress Approves Bill Supporting Human Space Exploration

China's Chengdu aiming to be world's next Silicon Valley

EXO WORLDS
Mr Xi in Space

China plans manned space launch in 2013: state media

China to launch manned spacecraft

Tiangong 1 Parked And Waiting As Shenzhou 10 Mission Prep Continues

EXO WORLDS
Crew Wraps Up Robonaut Testing

Station Crew Ringing in New Year

Expedition 34 Ready to Ring in New Year

New ISS crew docked at Space Station

EXO WORLDS
Arianespace to launch VNREDSat-1A built by Astrium for Vietnam

Arianespace says 2012 sales leapt by 30%

CSF Applauds Passage Of Risk-Sharing Regime Extension For Launch Industry

Rokot Launch Set for January 15

EXO WORLDS
15 New Planets Hint At "Traffic Jam" Of Moons In Habitable Zone

Within 'Habitable Zone,' More Planets than We Knew

At Least One in Six Stars Has an Earth-sized Planet

Exocomets may be as common as exoplanets

EXO WORLDS
Cloud computing expands in Latin America

LEON: the space chip that Europe built

That's not what I meant: A new phase in reading photons

Space Trash May Make Radiation Shields




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement