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Astronomers Find Part-Time Pulsar
Manchester, UK (SPX) March 8, 2006 Astronomers have discovered a very strange pulsar that transmits its radio signal only part of the time. The astronomers, using the 76-meter (247-foot) Lovell radio telescope at the University of Manchester's Jodrell Bank Observatory, found that the pulsar also seems to slow its rate of rotation by 50 percent when it is "on," compared to when it is "off." Pulsars are dense, highly magnetized neutron stars born in supernovas. They act like cosmic lighthouses because they project rotating beams of radio waves. "Pulsars are a physicist's dream come true, said team leader Michael Kramer. "They are made of the most extreme matter that we know of in the universe, and their highly stable rotation makes them super-precise cosmic clocks - but, embarrassingly, we do not know how these clocks work. This discovery goes a long way towards solving this problem." Reporting Feb. 23 in Science Express, an online service of the journal Science, Kramer and colleagues said the pulsar appears normal for about a week, then "switches off" for about one month before emitting pulses again. The pulsar, called PSR B1931+24, is unique in this behavior. Because it is quiet most of the time, it has been difficult to detect -which suggests there may be many other similar objects in the universe. "After the discovery of pulsars, theoreticians proposed that strong electric fields rip particles out of the neutron star surface into a surrounding magnetized cloud of plasma called the magnetosphere," said team member Andrew Lyne, "but for nearly 40 years, there had been no way to test whether our basic understanding was correct." The astronomers said they were delighted when they discovered that PSR B1931+24 slows down rapidly when it is transmitting. "We can clearly see that something hits the brakes when the pulsar is on," said team member Christine Jordan. The astronomers think the braking mechanism must be related to the radio emission and the processes creating it � such as the rotational energy carried by the wind of particles leaving the pulsar's magnetosphere. "Such a braking effect of the pulsar wind was expected but now, finally, we have observational evidence for it," said Duncan Lorimer, another team member. Kramer said the amount of braking could be related to the number of charges leaving the pulsar magnetosphere � something that theorists had proposed 37 years ago, and the new observations matched within 2 percent. "We were really shocked when we saw these numbers on our screens," Kramer said. "Given the pulsar's complexity, we never really expected the magnetospheric theory to work so well." Lyne called the finding "amazing," and added that, "after almost 40 years, we have not only found a new, unusual, pulsar phenomenon but also a very unexpected way to confirm some fundamental theories about the nature of pulsars." Community Email This Article Comment On This Article Related Links Jodrell Bank Stellar Chemistry, The Universe And All Within It
Young Galaxies Were Hostile To Life
Pasadena CA (SPX) March 7, 2006Scientists said Tuesday they have found evidence that the earliest galaxies in the universe could have been extremely hostile environments for life. |
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