It’s hard to learn much about a celestial explosion if you know neither its host environment nor how far away it was. For a given apparent brightness, distance determines energy output and the environment suggests some mechanisms and precludes others. For the majority class of gamma-ray bursts (the so-called long GRBs, which last longer than a few seconds), the breakthrough came in 1997, when the first detection of optical and x-ray afterglows made it possible to pinpoint them to young star-forming galaxies at cosmological distances measurable by redshift. Nowadays it is widely accepted that long GRBs are caused by unusually energetic supernova explosions of massive young stars (see Physics Today, August 2005, page 21).
There is, however, a distinct minority class of GRBs—those with burst durations shorter than two seconds—for which the determinations of distances and hosts are only now becoming available. The 6 October issue of Nature...
