May 16, 2008
Astronomers Discover Rare, Rapidly Spinning Pulsar
Astronomers have discovered a rare type of star called a pulsar that they believe is locked in an elongated orbit around a star much like the sun.
The spinning pulsar is called J1903+0327 and is located about 21,000 light years (About 6 trillion miles) from Earth. A pulsar is created when a massive star explodes as a supernova, astronomers said.
"The big question is"”how in the heck did this thing form, because it doesn't follow our standard models of how these things form," astronomer Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Virginia.
The object is known as a millisecond pulsar because of the way it spins on its axis 465 times per second.
Astronomers said pulsars typically found orbiting with another star have been doing so with another type of dying star called a white dwarf. In each case, they shared a perfectly circular orbit. But this one has a very elongated orbit around a star similar in size and composition to our sun.
Astronomer David Champion of the Australia Telescope National Facility said what they have found is a millisecond pulsar that is in the wrong kind of orbit around what appears to be the wrong kind of star. "Now we have to figure out how this strange system was produced."
The pulsar was detected with a radio telescope in Puerto Rico.
Classified as a rare type of neutron star, pulsars have strong magnetic fields that channel lighthouse-like beams of light and radio waves that whirl around as the star spins.
Pulsars typically spin once a second to about 10 or 20 times a second, but millisecond pulsars spin far more rapidly.
Astronomers believed that these started out as typical, slower-spinning pulsars, and then built up speed after material expelled from another star reached the pulsar's surface, giving it momentum.
"If you were to ask any astronomer if we would have found a system like this, they would have said no. So this is a very big surprise," Ransom said.
The scientists speculate a third star"”perhaps a neutron star or white dwarf"”might be orbiting with the other two. Ransom said scientists know of about 100 pulsars in two-star, or binary, systems, and this might be the first in a triple-star system.
The discovery was published in the journal Science.
Image Caption: A diagram shows a comparison of the sizes and strangely elliptical shapes of the orbits of the pulsar J1903+0327 and its apparently Sun-like companion star with the orbit of the Earth around the Sun. The sizes of the Sun and the possible companion star have been exaggerated by a factor of about 10, while that of the Earth has been exaggerated by a factor of about 1,000. The pulsar, with its magnetic field and beams of radiation, is too large by a factor of about 100,000. (NRAO/AUI/NSF)
On the Net:
National Radio Astronomy Observatory
Australia Telescope National Facility