An image of GRB 171205A, a gamma ray burst in a galaxy some 500 million light years away, near the time of its maximum brightness. Image: Izzo et al, Gran Telescopio Canarias
When low-mass stars like the Sun exhaust their nuclear fuel, they shed their outer layers and leave behind a dense, slowly cooling core – a white dwarf – and perhaps a colourful nebula serving as a cosmic tombstone of sorts.
But very massive stars suffer an altogether more violent fate, exploding in cataclysmic supernova blasts and, in some cases, even more extreme events known as gamma ray bursts and hypernovae. These detonations are much more energetic than a typical supernova, briefly outshining the brightness of their entire galaxy while giving birth to a collapsed neutron star or black hole.
The first known hypernova, detected immediately after a gamma ray burst, was discovered in 1998. Since then, astronomers have established a firm connection between GRBs and hypernovae, theorising that when the core of a star with more than 25 times the mass of the Sun implodes, two polar jets of gas are blasted outward, drilling through the star’s external layers and producing a torrent of gamma rays. The outer ...