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Impearls: Magnetars and Pulsars: The Pulsar Menagerie

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Earthdate 2004-05-29

The Pulsar Menagerie

Scores of extrasolar planetary bodies have been discovered over the past dozen years or so, but it somehow had escaped my notice anyway that the very first such planetary system beyond our own to be discovered orbits round a pulsar.  As Robert Irion points out in his piece “The Pulsar Menagerie” in Science's pulsar special: 1  “Indeed, more than 100 other planets are now known, although PSR B1257+12 is still the only burned-out corpse of a dead star known to have a planetary system.  […]  The masses and relative positions of the three planets are ‘shockingly similar to our inner solar system.’”  Shades of Arthur C. Clarke's most poignant short story “The Star”!

Impearls has featured several articles recently discussing the testing of Einstein's general relativity (here, here, and here), and it's worth mentioning in this context the pair of neutron stars (one pulsing, one not) orbiting round each other known as the “Hulse-Taylor binary” (PSR B1913+16), discovered in 1974.  “[T]he team showed that the two bodies inexorably spiral together, at exactly the rate predicted by Einstein 60 years earlier.  Gravitational waves carry away the lost orbital energy.  ‘It's indirect, like showing that radio waves exist because you know the radio transmitter uses power,’ Hulse says.  ‘But it was the first evidence for the existence of gravitational waves.’”

Just earlier this year came the sequel:

The latest stunner was anticipated for years: two pulsars deadlocked in a tight orbit.  The new system, detected by the Parkes Radio Telescope in Australia and announced in January, will likely provide even more stringent tests of general relativity than the Hulse-Taylor binary (Science, 9 January, p. 153).

Already, astrophysicists are mystified by the energetic interplay between the neutron stars.  Intense winds from the faster rotating pulsar create a tear-shaped shock wave around the slower pulsar.  Teams are probing this process as one pulsar dips behind the other, every 2.4 hours.

In one interpretation of the data, the fast pulsar is churning out 100,000 to 1 million times more charged gas than expected from the seething region above its surface, says theorist Jonathan Arons of UC Berkeley.  “The physics is not quite incredible, but it's close,” he says.


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