Earth was hit by an intense and unusual burst of light that could change our understanding of the universe, scientists have said.
Late last year, scientists spotted a 50-second burst of energy coming towards Earth known as a gamma-ray burst or GRB, which are the most powerful bursts in the universe. Immediately, researchers began looking for the afterglow these explosions leave behind, with this visible light being helpful in finding where the explosion came from.
But these researchers discovered something else instead: that the explosion appeared to come from a kilonova. These rare events only occur when a neutron star merges with another very compact object, either another neutron star or a black hole.
The study challenges our understanding of the origin of these durable GRBs. But it could also provide an exciting way to answer other questions about the universe, such as where its heaviest elements come from, which is still a mystery.
And the galaxy where the GRB comes from is also strange. It is young and continues to form stars – unlike the only other known nearby galaxy that has hosted such an event.
“This event is unlike anything we’ve seen before from a long gamma-ray burst,” said Jillian Rastinejad of Northwestern University, who led the study. “Its gamma rays resemble those of the bursts produced by the collapse of massive stars.
Since all other confirmed neutron star mergers we have observed have been accompanied by bursts lasting less than two seconds, we had every reason to expect this 50-second GRB to be created by the collapse of a massive star. This event represents an exciting paradigm shift for gamma-ray burst astronomy.
A paper describing the results, “A kilonova following a long-duration gamma-ray burst at 350 Mpc”, is published in the journal Nature today.
The explosion was first spotted in December 2021 by Nasa’s Neil Gehrels Swift Observatory and Fermi Gamma Ray Space Telescope. Since then, researchers have sought to categorize the explosion and understand where it may have come from.
Among other findings, they showed that the single event produced heavy elements that were about 1,000 times the mass of our Earth. This suggests that kilonovae are the main place where gold is produced in the universe.
And because the galaxy the GRB originated from is relatively close, scientists were able to observe it in an unusually good way. Additionally, it could help explain other gamma-ray bursts that don’t seem to match our understanding of their origin.
“It was a remarkable GRB,” said Benjamin Gompertz. “We don’t expect merges to last longer than about two seconds. Somehow this one propelled a jet for almost a full minute. It’s possible the behavior could be explained by a long-lived neutron star, but we can’t rule out that what we saw was a black hole-ripped neutron star.
“Studying more of these events will help us determine which is the correct answer and the detailed information we have obtained from GRB 211211A will be invaluable for this interpretation.
And scientists hope that turning on the James Webb Space Telescope will provide an even better view of the kilonovae. This telescope is able to capture images of distant astronomical objects and “sniff” their atmospheres, allowing it to see exactly what elements are present through a process known as spectroscopy.
“Unfortunately, even the best ground-based telescopes aren’t sensitive enough to perform spectroscopy,” Rastinejad said. “With the JWST, we could have obtained a spectrum of the kilonova. These spectral lines provide direct evidence that you have detected the heaviest elements.