NOT all gamma-ray bursts – those colossal blasts of energy that are thought to spew out when the core of a massive star collapses – are as energetic as astronomers thought. Two teams have now seen one that was much weaker than expected, and think that such half-hearted bursts may even be more numerous than their full-blooded counterparts.
The energies of gamma-ray bursts were thought to be well known, says Alicia Soderberg at the California Institute of Technology in Pasadena. But both Soderberg’s team and one from the Space Research Institute in Moscow have measured radiation from a gamma-ray burst called GRB 031203, and found that it had about a hundredth of the brightness of a typical burst (Nature, vol 430, p 646 and 648). This confirms that a similar weak burst seen in 1998 was not an aberration. And because these weaker bursts are relatively faint and hard to detect, there may be many more taking place out there.
Astrophysicist Stan Woosley of the University of California, Santa Cruz, says the new fainter bursts are probably coming from collapsing stars that for some reason are putting significantly less energy into gamma rays.
Advertisement