At the Gamma Ray 2001 conference in Baltimore, Luigi Piro of the Istituto Astrofisica Spaziale in
Rome presented new evidence linking gamma-ray bursts to dense regions of star
formation.
Gamma-ray bursts (GRBs) are by far the most powerful events known to occur
in the universe since the Big Bang. Their brightness can be enormous – it has been known to reach
1 billion times that of the combined emission from all of the stars in the host galaxy. The
mechanisms fuelling GRBs are, however, still unknown.
Piro and collaborators observed the
afterglow emission that follows GRBs and found evidence that the blast wave was braking against
very dense gas, such as would be found in regions where new stars were forming. The results
support the hypernova model of GRBs, in which the explosion of an extremely massive star
produces an enormous blast of material. This fireball expands at relativistic speeds. The
observations were made using NASA’s Chandra X-ray observatory and the Italian-Dutch
BeppoSax observatory.
Meanwhile, astronomers using the Parkes radiotelescope in Australia
have found 30 young pulsars, counterparts of otherwise unidentified galactic gamma-ray sources.
Previously, seven gamma-ray sources had been identified with pulsars. Pulsars are neutron stars
formed by the collapse of massive stars during supernova explosions. Their intense magnetic fields
are expected to make them prolific sources of high-energy radiation.
