Published online 12 August 2010 | Nature | doi:10.1038/news.2010.401

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Home computer finds rare pulsar

The Einstein@Home volunteer-computing project makes its first discovery.

Data gathered by the world's largest radio dish in Arecibo, Puerto Rico, is later sifted for puslars by the Einstein@Home project.Louie Psihoyos/Science Faction/Corbis

A rare isolated pulsar with a very low magnetic field has been discovered by a volunteer-computing initiative, researchers report today in the journal Science1.

When Bruce Allen, director of the Einstein@Home distributed-computing project, first contacted Chris and Helen Colvin from Ames, Iowa, to tell them that their home computer had made a significant discovery while running the project's software as a screensaver, they did not believe he was serious. The Colvins are among 262,000 volunteers in 192 countries who have loaded and run the Einstein@Home software on their computers.

"This is the first time an astronomical object has been discovered by this kind of distributed-computing project," says Allen, a director of the Max Planck Institute for Gravitational Physics in Hannover, Germany. "I'm really excited we found something."

Like its better known counterpart, SETI@home, Einstein@Home uses the time when volunteers' computers are idle to crunch through massive data sets looking for patterns. Whereas SETI@home searches through radio observations for signals of possible extraterrestrial intelligence, Einstein@Home sends out data from the Laser Interferometer Gravitational Wave Observatory to be analysed for the presence of gravitational waves.

After a four-year search for gravitational waves drew a blank2, Allen decided to dedicate 35% of Einstein@Home's computing time to searching for signals from pulsars — collapsed neutron stars that emit beams of radiation along their axis as they spin — in radio observations taken at the Arecibo Observatory in Puerto Rico. "Searching for gravitational waves is a long-term proposition and I thought it would be fun for Einstein@Home volunteers to have something that could be found at a rate of one or two a year," says Allen.

Einstein@Home volunteers Chris and Helen Colvin.Chris Colvin

The first of the new data were sent out in March 2009, and in June, the Colvins' computer scored a hit: the detection of a previously unknown pulsar that was emitting a radio pulse at a rate of 41 per second, faster than 90% of known pulsars. Three days later, the pulsar was redetected by computers belonging to the music informatics department at Johannes Gutenberg University in Mainz, Germany, where the system administrator Daniel Gebhardt had uploaded Einstein@Home. Gebhardt says he has no scientific background but is a big fan of distributed computing: "I've never thought I could find anything. Nice feeling." Allen's collaborators followed-up with observations at the Robert C. Byrd Green Bank Telescope in West Virginia to confirm that the new pulsar was real.

Pulsar lottery

Named PSR J2007+2722, the fast spin rate of the pulsar suggests that it is a 'recycled' pulsar that has recently accreted material from a companion star. As the material collapsed onto the star, that star's rate of spin increased — in the same way that an ice skater speeds up their rotation by pulling in their arms. Repeat measurements of the pulsar's spin suggest it is slowing down again at a remarkably slow rate, which implies a weak magnetic field; a strong field would produce a braking effect which would cause the pulsar to spin down sooner. Radio signals from PSR J2007+2722 are not shifted in frequency as would be expected if it was currently orbiting another star, suggesting that the companion has since gone supernova, leaving the pulsar isolated. There are only about a dozen recycled isolated pulsars known, and PSR J2007+2722 is thought to be the fastest spinner of the bunch. The newly found object is located 17,000 light years away, in the direction of the constellation Vulpecula.

As well as PSR J2007+2722, the Einstein@Home project has redetected 120 previously known pulsars. Those results were made public on the project's web site, but the latest finding was held back for publication1.

Cole Miller, an astronomer at the University of Maryland in College Park, says it is nice that the pulsar was detected with Einstein@Home, because it validates the idea of using massive volunteer-computing projects to detect new sources of radiation in astronomical data sets. But he adds that the find is not tremendously noteworthy, as the number of new pulsars found is small compared with the number of redetections, suggesting that the extra computing power has not made a big difference. He points out that other distributed computing projects have already made significant findings; for example, Rosetta@home has made important discoveries in protein folding, and the Galaxy Zoo project has classified 1.25 million individual galaxies as either elliptical or spiral (see 'Citizen science: People power').

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But Einstein@Home is one of the biggest distributed computing projects, and some experts on radio pulsars are thrilled. "I think it's really exciting," says Paul Ray, an astrophysicist at the US Naval Research Laboratory in Washington DC. Ray is working with a large data set of γ-ray observations taken with the NASA-operated Fermi Gamma-ray Space Telescope, and says he wants to set up a similar computing project to detect pulsars emitting γ-rays. "We've found 24, but we know there are more we aren't able to find," he says.

Ray hopes that the publicity surrounding the detection of PSR J2007+2722 will encourage more people to enrol their computers in projects such as Einstein@Home and make more computing power available. "It would be very exciting if the first true measurement of a gravitational wave came from someone running Einstein@Home," he says.

Helen Colvin says that she and Chris loaded Einstein@Home after a period of running SETI@Home because it seemed more likely to get a result some day. Still, she is surprised to own the computer that actually found something. "It was a bit like winning the lottery," she says. "The odds aren't in your favour." 

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