Astronomers can spend years analyzing signals from radio telescopes to find a new pulsar, a dense, rapidly rotating star that emits regular blasts of radio waves. However, three citizen scientists have discovered an unusual pulsar by doing virtually nothing—and it may be a record-breaker to boot.
Pulsars form when massive stars (between eight and 20 times the mass of the sun) run out of fuel and contract under their own gravity. As the star shrinks, it rotates faster and accelerates protons and electrons on its surface, creating a beam of radiation that emanates from its magnetic poles. If those poles are not aligned with the star's axis of rotation, the beam sweeps around with the spinning star like a lighthouse beam.
Sometimes pulsars are found in binary systems with a companion star. To detect pulsars in these systems, astronomers must correct for the Doppler effect—the change in frequency of a wave due to the motion of its source relative to the observer—because the star moves toward and away from Earth in its orbit. However, making the correction is a tricky and time-consuming task, says physicist Benjamin Knispel of the Max Planck Institute for Gravitational Physics in Hannover, Germany, co-author of the paper about the discovery. "The exact orientation and size of the orbit is unknown, so a wide range of possible combinations has to be explored, leading to lengthy computer analyses," he says.
This is where the citizen science project Einstein@Home comes in. Similar to the well-known SETI@home, which is searching for signals from extraterrestrial life, Einstein@Home harnesses the idle time of home computers belonging to volunteers across the globe to crunch large amounts of data. In this case, that involves analyzing radio signals from the Arecibo Observatory in Puerto Rico to correct for the Doppler effect in 6661 possible orbit combinations. Currently, more than 100,000 computers are helping with the calculations.
In a paper published online today in Science, researchers announce that they pinpointed a pulsar thanks to Einstein@Home. The three volunteers whose computers analyzed the data that revealed the star are Daniel Gebhardt, a systems administrator from Mainz, Germany, and husband-and-wife team Chris and Helen Colvin of Ames, Iowa; he is a systems architect, and she is a software tester. They have been officially credited with the discovery. And rather than finding a run-of-the-mill pulsar, these citizen scientists may have stumbled across one that is spinning at record-breaking speed.
Over time, pulsars slow down as they lose energy through their jets of radiation. But the pulsar discovered by Einstein@Home is spinning quickly even though it isn't young. The leading explanation, says Knispel, is that it gobbled up matter from a companion star that has since been expelled from the binary system. If the pulsar did form in this way, it is the fastest-spinning example of this type, rotating once every 0.0245 seconds—that's 15% faster than the previous record-holder.
Astronomer Stephen Thorsett of the University of California, Santa Cruz, says that although the finding won't revolutionize our understanding of such pulsars, the discovery is nonetheless exciting because it stemmed from a volunteer computer project. "The challenges will be even bigger for analyzing data from the next generation of large radio telescopes," he says. "But as desktop computers keep getting more powerful, and more volunteers join, these types of distributed computing projects are an attractive model for handling the torrent of data that we will get."