Image: Parkes Survey
Despite some 30 years of searching, gamma-ray observatories have not targeted many sources of high-energy radiation. Indeed, fewer than half of the gamma-ray sources observed using the Energetic Gamma Ray Experiment (EGRET) instrument on board the Compton Gamma Ray Observatory satellite are known.
But scientists have suspected that young pulsars might prove very likely candidates¿and early results from an as yet incomplete survey now give further credence to that idea. An international team of astronomers using the Parkes 64-meter radio telescope in Australia announced yesterday at the Gamma-Ray Astrophysics 2001 symposium in Baltimore the discovery of roughly 30 new young pulsars¿two of which correspond in position to previously unidentified gamma-ray sources.
Both of these pulsars¿neutron stars formed in supernova explosions¿ appear to be particularly energetic and young. PSR J1420-6048 looks to be about 13,000 years old, and PSR J1837-0604, some 34,000 years old. In addition, both pulsars have increasing rotation periods, spinning that indicates they are losing energy fast. "For this reason alone one would expect that they should be observable as gamma-ray sources," said Nichi D'Amico of the Osservatorio Astronimico di Bologna in Italy.
The Parkes survey will continue to seek young, distant pulsars within five degrees of the Galactic Plane. But already it has turned up more than 600, nearly doubling the number found in earlier searches. In the image shown, the blue dots indicate all known pulsars. The red dots mark those found in the Parkes survey, and the yellow dots represent the new energetic radio pulsars.