In a universe full of messy blasts of energy, astronomers have found a remarkable sharpshooter. A newly detected pulsar squeezes off bursts of light each lasting just 43 microseconds. That makes this pulsar an extremely accurate clock, one that will help astrophysicists understand how some compact stars spin up to fantastic speeds.
Pulsars are the collapsed cores of massive stars that die in supernova explosions. Gravity crushes the core into a neutron star that packs more than the mass of our sun into a ball about 20 kilometers wide. Newborn neutron stars often spin fiercely and spew cone-shaped jets of energy into space, which rotate in and out of our view like the beacons in lighthouses. Such pulsars slow down and fade after millions of years. However, an ancient pulsar can get "recycled" if a companion star dumps gas onto the pulsar's surface. The infalling matter revs up the old pulsar until it spins hundreds of times per second.
A team led by graduate student Bryan Jacoby of the California Institute of Technology in Pasadena found several recycled pulsars recently with the 64-meter Parkes radio telescope in New South Wales, Australia. One of them, called PSR J1909-3744, emits an extraordinarily quick burst of energy, lighting up for just 43 microseconds--a "stunningly narrow" window of time, Jacoby says. The team's find will appear in a forthcoming issue of Astrophysical Journal Letters.
The pulsar's rotation has held rock steady at 339 times per second during 2 years of study. That makes PSR J1909-3744 one of the best astrophysical clocks yet found, Jacoby says. Researchers will monitor this and other recycled pulsars for subtle changes in timing that might reveal passing gravitational waves--warps in the fabric of spacetime rippling outward from the collisions of enormous black holes. Jacoby's team also expects to gauge the mass of the new pulsar by observing its interactions with its tiny companion, a white dwarf left behind after the companion star shed most of its gas into space.
That measurement would be a first for a recycled pulsar--and a crucial step in understanding the physics of neutron stars, comments astrophysicist Deepto Chakrabarty of the Massachusetts Institute of Technology in Cambridge. In particular, a pressing question is how much matter a pulsar can accumulate before it gets too massive and plunges into a black hole. "I'm writing the name of this [pulsar] on my whiteboard," Chakrabarty says. "It's definitely one to watch."
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