Figure 1
Out of our galaxy
The Burst and Transient Source Experiment (BATSE), which was part of NASA's Compton Gamma-Ray Observatory, detected over 2700 gamma-ray bursts between 1991 and 2000. These were found to be distributed evenly across the sky. The fact that none were concentrated in the Milky Way ruled out most theories that linked gamma-ray bursts to neutron stars in our galaxy. It seemed instead that the bursts had a cosmological origin, although the BATSE data alone could not prove this. Here, each dot represents the direction of a gamma-ray burst, with the intensity indicated by the different colours (increasing from blue to red).