Gamma-ray bursts are by far the brightest and most powerful explosions in the Universe, second only to the Big Bang itself. So it might seem a bit surprising that a group of them has gone missing.
A single gamma-ray burst (GRB) can easily outshine an entire galaxy containing hundreds of billions of stars. Powerful telescopes can see them from clear across the Universe. And because the deeper you look into space, the farther back in time you see, astronomers should be able to see GRBs from the time when the very first stars were forming after the Big Bang.
Yet they don’t. Gamma-ray bursts from that early epoch seem to be missing, and astronomers are wondering where they are.The answer eventually came from Stan Woosley, a theoretical astrophysicist at the University of California in San Diego. He suggested that when young, supermassive stars with low metal content collapse under their own weight to form black holes, the stars’ rotation funnels the explosive energy into two streamlined jets that shoot out from the stars’ poles, like the axis of a gyro. We only see the burst if one of these two jets happens to be pointed toward Earth. The concentration of energy into narrow jets is why GRBs that we do observe appear so remarkably bright.
The first waves of star formation after the Big Bang should have produced plenty of metal-poor supermassive stars ripe for collapse. If true, GRBs from that epoch should be abundant. So where are they?