Artistic representation of two gamma-ray bursts (or GRBs), one of standard duration and one ultra-long. The blue star in the background produces the standard-duration one. It is a Wolf-Rayet star of a size comparable to that of the Sun, but with a mass at least ten times greater. Instead, the star in the foreground is a supergiant, whose gravitational collapse can produce a gamma-ray burst of several hours, such as that of the event named GRB 111209A [Mark A. Garlick]

Gamma-Ray Bursts and Collapsing Stars

Gamma-ray bursts, or GRBs, are among the most energetic phenomena in the Universe. They are produced by the merging of neutron stars, by the gravitational collapse of large-mass stars or by the tidal destruction of a star by a black hole. In a short time, GRBs can release as much energy as that emitted by an entire galaxy over the course of a year

A magnetar giant flare

Visible light is only a small portion of the electromagnetic spectrum. It contains non-particularly energetic photons, with energies ranging from 1.6 to 3.4 electron-volts. As the wavelength of photons decreases, the energy transported increases. Gamma rays are located at the upper end of this scale, with wavelengths in the order of picometers — less than the diameter of an atom — and energies that can exceed hundreds of gigaelectron-volts (GeV), that is, many billions of times greater than that carried by visible light.

It is not surprising, therefore, that gamma rays are the messengers of some of the most energetic events that happen in the cosmos. They include super-flares from magnetars (neutron stars with…