Cannibalizing pulsar lures astronomers.Cannibalizing pulsar pulsar, in astronomy, a neutron star that emits brief, sharp pulses of energy instead of the steady radiation associated with other natural sources. The study of pulsars began when Antony Hewish and his students at Cambridge Univ. lures astronomers Like a revved-up giant lighthouse, a rapidly rotating neutron star near the Milky Way's center beams radio waves Radio waves Electromagnetic energy of the frequency range corresponding to that used in radio communications, usually 10,000 cycles per second to 300 billion cycles per second. toward Earth at a dizzying rate of 86 times a second. That phenomenon alone would capture the interest of astronomers. But the haphazard variation in the intensity of this newly discovered star's radio signals -- which can disappear several times a week for more than six hours -- further intrigues scientists. Discovery of the pulsar's intermittent signal, researchers say, strongly suggests the neutron star is eating away at an unseen orbiting companion, tearing off surface matter that erratically eclipses the neutron star's radio beam. Located in the Terzan 5 globular cluster, PSR PSR Pulsar PSR Poster PSR Physicians for Social Responsibility PSR Psychosocial Rehabilitation PSR Pacific School of Religion PSR Policy and Survey Research PSR Project Study Report PSR Pre-Sentence Report PSR Pressure-State-Response PSR Puget Sound Region 1744-24A is only the second eclipsing double-star pulsar ever discovered. The find may add new details to the evolution and history of these radio-emitting cannibals, says Andrew G. Lyne of the University of Manchester The University of Manchester is a university located in Manchester, England. With over 40,000 students studying 500 academic programmes, more than 10,000 staff and an annual income of nearly £600 million it is the largest single-site University in the United Kingdom and receives in England. In comparison with the "black widow" -- a 1.6-millisecond pulsar spotted two years ago some 3,000 light years from Earth (SN: 7/30/88, p.72) -- the newly discovered pulsar spins about 10 times more slowly and appears to have a larger, more massive companion on which to feast. Each of these pulsars radiates enough energy to heat material on its companion's surface. This creates a "wind" of particles that can eclipse radio emissions from the rapidly spinning pulsar, notes Jacob Shaham of Columbia University in New York City New York City: see New York, city. New York City City (pop., 2000: 8,008,278), southeastern New York, at the mouth of the Hudson River. The largest city in the U.S. . But several features of the newly discovered radio-emitter, including its fluctuating eclipse period e·clipse period n. The period of time between infection by a virus and the appearance of the mature virus within the cell. eclipse period the time interval between viral penetration and the production of progeny virions. , indicate this pulsar may be undergoing a different, possibly earlier, stage of evolution than the "black widow" -- one in which gravitational grav·i·ta·tion n. 1. Physics a. The natural phenomenon of attraction between physical objects with mass or energy. b. The act or process of moving under the influence of this attraction. 2. capture of matter from the companion also contributes to the eclipsing phenomenon, he and Lyne say. Shaham speculates that the companion's radius is just large enough for the pulsar to occasionally steal a large blob of gas, which then separately orbits the pulsar and temporarily blocks its radio emissions. He adds that any gas that comes closer to the pulsar must penetrate that star's magnetic field, creating X-ray bursts in the process. Such bursts could account for the pulsed X-ray emissions in Terzan 5 detected by a Japanese satellite in 1980, Shaham, Lyne and others speculate. Lyne and an international team of co-workers describe their stellar discovery in the Oct. 18 NATURE. |
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