Washington, May 16 : Astronomers have been left puzzled after they discovery of a stellar pair - a speedy spinning pulsar in an elongated orbit around an apparent Sun-like star, a combination never seen before.
Astronomers first detected the pulsar, called J1903+0327, as part of a long-term survey using the National Science Foundation's Arecibo radio telescope in Puerto Rico in 2006.
They followed up the discovery with detailed studies using the Arecibo telescope, the NSF's Robert C. Byrd Green Bank Telescope (GBT) in West Virginia, the Westerbork radio telescope in the Netherlands, and the Gemini North optical telescope in Hawaii.
The pulsar, a city-sized superdense stellar corpse left over after a massive star exploded as a supernova, is spinning on its axis 465 times every second. Nearly 21,000 light-years from Earth, it is in a highly elongated orbit that takes it around its companion star once every 95 days.
An infrared image made with the Gemini North telescope in Hawaii shows a Sun-like star at the pulsar's position.
If this is an orbital companion to the pulsar, it is unlike any companions of other rapidly rotating pulsars. The pulsar, a neutron star, also is unusually massive for its type.
"This combination of properties is unprecedented. Not only does it require us to figure out how this system was produced, but the large mass may help us understand how matter behaves at extremely high densities," said Scott Ransom of the National Radio Astronomy Observatory.
Pulsars are neutron stars whose strong magnetic fields channel lighthouse-like beams of light and radio waves that whirl around as the star spins.
Typical pulsars spin a few times a second, but some, like the newly detected one, are much faster, rotating hundreds of times a second. They are called millisecond pulsars.
Astronomers think most millisecond pulsars are sped up by material falling onto them from a companion star. This requires the pulsar to be in a tight orbit around its companion that becomes more and more circular with time.
The orbits of some millisecond pulsars are the most perfect circles in the Universe, so the elongated orbit of the new pulsar is a mystery.
"What we have found is a millisecond pulsar that is in the wrong kind of orbit around what appears to be the wrong kind of star," said David Champion of the Australia Telescope National Facility. "Now we have to figure out how this strange system was produced," he added.
"This is a fascinating object that has a lot to teach us about physics. It's going to be exciting to peel away the mystery of how this thing came to be," said Champion.