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Discovery The first pulsar was discovered in 1967, by Jocelyn Bell Burnell and Antony Hewish of the University of Cambridge, UK. Initially baffled as to the unnaturally regular nature of its emissions, the pair dubbed their discovery LGM-1, for "little green men"; their pulsar was later dubbed CP 1919, and is now known by a number of designators including PSR 1919+21. The word pulsar is a contraction of "pulsating star", and first appeared in print in 1968: "An entirely novel kind of star... came to light on Aug. 6 last year and, ... was referred to by astronomers as LGM (Little Green Men). Now... it is thought to be a novel type between a white dwarf and a neutron ''sic''. The name Pulsar (Pulsating Star) is likely to be given to it. ... Dr. A. Hewish ... told me yesterday: '... I am sure that today every radio telescope is looking at the Pulsars." Astrophysicist Peter A. Sturrock writes that "when the first regular radio signals from pulsars were discovered, the Cambridge scientists seriously considered that they might have come from an extraterrestrial civilization. They debated this possibility and decided that, if this proved to be correct, they could not make an announcement without checking with higher authorities. There was even some discussion about whether it might be in the best interests of mankind to destroy the evidence and forget it!" (Sturrock, 154) CP 1919 emits in radio wavelengths, but pulsars have subsequently been found to emit in the X-ray and/or gamma ray wavelengths. Hewish received the 1974 Nobel Prize in Physics for this and related radio astronomy work. Pulsar classes Three distinct classes of pulsars are currently known to astronomers, according to the source of energy that powers the radiation: Although all three classes of objects are neutron stars, their observable behaviour and the underlying physics are quite different. There are, however, connections. For example, X-ray pulsars are probably old rotation-powered pulsars that have already lost most of their energy, and have only become visible again after their binary companions expanded and began transferring matter on to the neutron star. The process of accretion can in turn transfer enough angular momentum to the neutron star to "recycle" it as a rotation-powered millisecond pulsar. Glitch prediction In June 2006, astronomer John Middleditch and his team at LANL announced the first prediction of glitches, with observational data from the Rossi X-ray Timing Explorer. They used observations of the pulsar PSR J0537-6910. Application The study of pulsars has resulted in many applications in physics and astronomy. Striking examples include the confirmation of the existence of gravitational radiation as predicted by general relativity and the first detection of an extra-solar planetary system. Significant pulsars Notes | ||||||||||
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