Astrophysicists measured light from exploding stars called supernovae to arrive at the most precise limits yet for the composition of the universe – Copyright AFP/Behrouz MEHRI File
Astrophysicists have long believed that only the collapses of massive stars could generate large gamma-ray bursts. Now a new finding shows that neutron star mergers can generate long gamma-ray bursts.
Gamma-ray bursts are the brightest and most energetic explosions to occur in the universe since the Big Bang. These fall into two classes: short (2 seconds or less) or long (more than 2 seconds). Scientists have generally held the view that these two types have very different origins. The new finding refutes this.
Evidence for the new assumption comes from what is known as a ‘kilonova’, an event that is only generated from neutron star mergers, followed by a long gamma-ray burst. This new information is not only of interest in terms of astronomical events, but provides new clues in the search for heavy elements.
Kilonovae produce gamma-ray bursts and strong electromagnetic radiation due to the radioactive decay of heavy nuclei from the r-process. the gloss level produced of the event is 1000 times greater than that of a classical nova.
There is a difference between a supernova and a kilonova. This is that kilonovae form when two neutron stars collide, while a supernova occurs when a white dwarf that is 1.44 (or more) solar masses or a star that is 8 (or more) solar masses explodes, producing a neutron star.
The research arose after Northwestern University scientists detected a 50-second long gamma-ray burst in December 2021 (called GRB211211A and located about 1.1 billion light-years away in a galaxy called SDSS J140910.47+ 275320.8). The team began looking for the afterglow of the long GRB, which is an incredibly bright, rapidly fading burst of light that often precedes a supernova.
However, contrary to expectations, scientists discovered evidence of a kilonova. This in itself is a rare event. The kilonova recorded a burst of luminosity, duration, and color similar to that accompanying the binary neutron star mergers detected by gravitational waves described above.
One of the leading scientists. Jillian Ratinejad states: “This event is unlike anything we have seen before a long gamma-ray burst… This event represents an exciting paradigm shift for gamma-ray burst astronomy.”
The consequence of the discovery may later be how astrophysicists approach the search for heavy elements, such as platinum and gold, and thereby offer new clues about the formation of the cosmos.
the investigation has been published in scientific journal Nature. The paper is titled “A kilonova after a long-duration 350 Mpc gamma-ray burst.”
