Astronomers have found a blast of gamma rays from space that seems to have been caused by two stellar corpses smashing together in a way that’s never been seen before
By Leah Crane
22 June 2023
Artist’s impression of a gamma ray burst that may have come from dead stars crashing into each other
International Gemini Observatory/NOIRLab/NSF/AURA/M. Garlick/M. Zamani
A strange flash of gamma rays from space is upending our ideas on stellar collisions. This gamma ray burst (GRB) seems to have come from two stars smashing together near the centre of an old galaxy, a vastly different origin from other events like it.
There are two types of GRBs: short ones, which last 2 seconds or less, and long ones. Long GRBs are generally thought to occur when a massive star explodes in a supernova, whereas most short GRBs seem to come from binary neutron stars – incredibly dense stellar corpses – smashing together.
The one in question, called GRB191019A, was a long GRB, but nevertheless seems to have come from two dead stars, or possibly a star and a black hole, colliding.
Advertisement
Anya Nugent at Northwestern University in Illinois and her colleagues used data from six observatories to dig into the details of the powerful blast, which occurred in 2019 and lasted a little over 1 minute. They found that the burst came from close to the centre of a galaxy about 3.3 billion light years away, but saw no hint of the supernova expected to be required for a long GRB.
Read more:
Gamma ray bursts could help unravel how fast the universe is expanding
Those supernovae tend to be more common in young, active galaxies, but this galaxy is extremely old. Most of its massive stars have already gone through the main phase of their lives and evolved into neutron stars, white dwarfs and black holes. Because GRB191019A came from so close to the centre of its galaxy, where those stellar corpses whizz around in abundance, the researchers found that it is most likely two of them collided to create this blast of radiation.