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Space Science

New Class of Pulsars Discovered 93

xyz writes "NASA's Fermi Gamma-ray Space Telescope has discovered a new class of pulsars which emit purely in gamma rays. A pulsar is a rapidly spinning neutron star, and of the nearly 1,800 cataloged so far, only a small fraction emit at frequencies higher than radio waves. The gamma-ray-only pulsar, which lies within a supernova remnant known as CTA 1, is silent across parts of the electromagnetic spectrum where pulsars are normally found, indicating a new class of pulsars. It is located 'about 4,600 light-years away in the constellation Cepheus. Its lighthouse-like beam sweeps Earth's way every 316.86 milliseconds. The pulsar, which formed in a supernova explosion about 10,000 years ago, emits 1,000 times the energy of our sun.'"
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New Class of Pulsars Discovered

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  • by glitch23 ( 557124 ) on Sunday November 02, 2008 @12:58PM (#25603285)

    It's not mentioned in the article, and I assume it's so obvious that it was ruled out before announcement, but is there anything to suggest that the pulsar is pulsing across all frequencies up to Gamma, and that intervening matter is simply blocking all but the high-energy Gamma portion of the pulse?

    Yes it was mentioned:

    This discovery by Fermi is different because it is a purely gamma-ray pulsar. The star is silent across parts of electromagnetic spectrum where pulsars are normally found and hints at a whole population of previously unsuspected pulsars waiting to be picked out of the heavens.

  • by rasputin465 ( 1032646 ) on Sunday November 02, 2008 @01:16PM (#25603385)

    Isn't earth in danger of an extinction event when a gamma ray burst occurs from something about 6,000 light years away?

    Although this thing does emit gamma rays, in discreet packets, this is not an example of the phenomenon knows as Gamma Ray Bursts (GRBs). The "burst" in a genuine GRB lasts much longer (seconds or minutes as opposed to milliseconds), happens only once, and contains orders of magnitude greater energy.

    So when we say we're screwed if a GRB happens within 6,000 lt-yr of Earth (and it's pointed in our direction), that's absolutely true, but it doesn't apply to pulsars.

  • by Gil-galad55 ( 707960 ) on Sunday November 02, 2008 @02:18PM (#25603877)
    The neutron star surface does emit thermal X-rays because it is hot. However, the electromagnetic radiation originates outside the neutron star, in its magnetosphere.

    Pulsars have extremely strong magnetic fields and rotate anywhere from 1-to-1000 times a second. Just like an electric generator, this produces huge electromagnetic fields, and these accelerate electrons to very high energies indeed. These electrons than bang into photons and give them a large chunk of energy in a process called inverse Compton scattering, and we get gamma rays.

    (This is the so-called leptonic channel; it is also possible some gamma rays are produced via pions, but the origin of the energy is the same: the huge electromagnetic fields generated by this spinning magnetic dipole.)

  • by Gil-galad55 ( 707960 ) on Sunday November 02, 2008 @03:47PM (#25604537)
    Sorry, its high luminosity is more than offset by its distance of kiloparsecs. The relevant quantity is flux, which goes like luminosity/distance^2.

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