A new pulsar has been discovered with the help of a volunteer network of 250,000 home and office computers around the world, including Canada.
The discovery of the fast-rotating neutron star about 17,000 light years from Earth, found with assistance from the Einstein@Home project, marks the first time such volunteer "distributed computing" has resulted in a significant astronomical find.
"The way it was done is really the highlight of the story," said James Cordes, an astronomer at Cornell University in Ithaca, N.Y., who heads an international scientific consortium dedicated to finding and studying pulsars.
Members of the consortium co-authored the findings published online Thursday in Science Express.
A pulsar is a type of neutron star, which is created in the core of a massive star during a supernova explosion and is the most dense object known. A pulsar shines beams of high-energy radiation and is called a pulsar because the radiation pulses in and out of the Earth's line of sight as the star spins.
The chunk of data that precipitated the latest pulsar discovery was collected at the Arecibo Observatory in Puerto Rico, the largest single-dish radio-telescope in the world, in February 2007. It was broken up and sent to the computers of more than 300 volunteers around the world.
U.S., German volunteers got lucky
The home computer in Chris and Helen Colvin's basement in Ames, Iowa, finished processing the key data this past June 11 and a similar computer owned by Daniel Gebhardt in Mainz, Germany, completed processing the same data on June 14.
Einstein@Home was originally started in 2005 to search for gravity waves, but now also looks for pulsars. Since the network's founding, more than 262,000 volunteers' computers have completed some data processing and had their results validated. About 100,000 download work from Einstein@Home servers in a given week.
The five countries with the most Einstein@Home volunteers, in descending order are:
Benjamin Knispel, a graduate student at the Max Planck Institute for Gravitational Physics in Hannover in Germany and the lead author of the paper, looked at the data on July 10 "and immediately saw that there was something interesting there," said Knispel's supervisor, Bruce Allen, at a news conference Thursday.
Allen is leader of the Einstein@Home project and director for the Max Planck Institute for Gravitational Physics.
Cordes said the interesting object proved to be a neutron star rotating 40 times a second. It is a little bit unusual because of its low magnetic field compared with other pulsars.
"We aren't quite sure how it was formed," he said. "We think it came about originally being in a binary system, that is, orbiting another star."
The other star likely exploded as a supernova at some point, separating it from the pulsar.
There are about 50 distributed computing projects around the world that rely on members of the public to volunteer unused computing power from their home computers to help process scientific data.
"A lot of the times, these computers aren't doing anything. They're just sitting idle," said Allen. However, he added, the collective power of those idle computers is "substantially greater than [the computing power of] the largest supercomputers built."
Electrical power worth millions
He added that the electrical costs alone of running those home computers while they are being used by the project would amount to a few million dollars a year — a significant donation.
Volunteers, who don't need any scientific or technical background, install the project's software on their home PCs and it runs in the background while their computer is on. It doesn't require any other intervention.
The project gathers data from the Arecibo Observatory and distributes small chunks to the Einstein@Home network for processing. That results in a list of "candidates" that might be pulsars, which are sent to astronomers in the pulsar consortium.
"Many of these candidates are not actually really pulsars at all," said Ingrid Stairs, who is an associate professor of astronomy at the University of British Columbia, a member of the consortium that conducts research at Arecibo Observatory and a co-author of the paper.
"A human effort stage is necessary to sort of look at the candidates and say, 'Yes, this is probably worth following up' or, 'No, this is probably not worth following up.'"
A postdoctoral fellow in Stairs's research group, Marjorie Gonzalez, did some of the followup observations of the new pulsar at the Arecibo Observatory. Other Canadian co-authors included Stairs's PhD student Laura Kasian and McGill University physicist Slavko Bogdanov.
Stairs said Arecibo data is processed not just by Einstein@Home, but also by two other computing "pipelines" that use university computing clusters instead of volunteers.
All the pipelines process the same data, but are sensitive to different things. For example, Einstein@Home is more sensitive to pulsars with a very tight orbit, she said.
"They're a bit complementary, although obviously in many cases there's opportunities for pipelines to find the same thing," Stairs added. "In a way, it's good to have the checks against each other."She estimated that about 2,000 pulsars are known and about 1,300 have been detected in the past 12 years. And she said while the discovery method for this one was unique, the pulsar itself "is not really all that special."
But Cordes said Einstein@Home has already led to another candidate that scientists are trying to confirm and describe, and he's hoping for more in the future.
The "holy grail" would be a pulsar orbiting around another object once every hour or less, he said. That would allow scientists to monitor it and test Einstein's theory of relativity precisely. Another item on the wish list is a pulsar orbiting around a black hole.
"Obviously, those are rare objects, but we have the potential of finding them in the Einstein@Home analysis."