A rare cosmic collision like one of the universe’s ‘gold mills’

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The unusually bright burst of light detected by multiple telescopes in December 2021 was the result of a rare cosmic explosion that created a wealth of heavy elements like gold and platinum.

This gamma-ray burst, named GRB 211211A, lasted about a minute. Gamma ray bursts are some of the most powerful and bright explosions in the universe, and can range in length from a few milliseconds to several hours.

The duration of the explosion indicated that it was caused by a massive star exploding while dying in a supernova. But the fallout from the gamma-ray burst was fainter and faded more quickly than those from supernovae, and astronomers analyzed the event by spying an excess of infrared light.

said Wen Fei-fung, assistant professor of physics and astronomy in Northwestern University’s Weinberg College of Arts and Sciences and first author and co-author of one of the four studies published about Wednesday’s event in the journal natural astronomy.

“We image a source in different filters to get the color information, which helps us identify the source’s identity. In this case, the reds predominated, and the blues faded more quickly. This color evolution is a hallmark of kilonovas, and kilonovas can only come from star mergers.” neutron”.

Kilonovas are rare, massive explosions caused by catastrophic collisions between neutron stars, the incredibly dense remnants of supernovae.And the Or collisions between neutron stars and black holes.

After determining that a kilonova created infrared light, astronomers were even more baffled by a gamma ray burst Duration. The gamma-ray bursts from these rare explosions were only observed for less than 2 seconds, but this signal lasted for at least 1 minute.

“When we followed this long burst of gamma rays, we expected that it would lead to evidence of massive star collapse,” Fung said. “Instead, what we found was very different. When I entered the field 15 years ago, it was clear that long gamma-ray bursts come from massive collapses of stars. Not only does this unexpected discovery mark a major shift in our understanding, but it also opens a new window for discovery.” Excitingly.”

Neutron stars are compact cosmic objects, so researchers never expected that they would contain enough matter to create a gamma-ray burst that could last for about a minute.

The explosion occurred in a galaxy It is about 1 billion light-years away from Earth. Since the event occurred relatively recently, in astronomical terms, astronomers have used multiple telescopes to gather unprecedented detail.

“We found that this one event produced about 1,000 times the mass of Earth in very heavy elements. Dr. Matt Nichol, assistant professor at the University of Birmingham in the UK and co-author of one of natural astronomy Studies in a statement.

The newly observed properties of this event are changing the way astronomers understand gamma ray bursts, or GRBs.

said Bing Zhang, professor of astrophysics at the University of Nevada, Las Vegas, and co-author of one of the natural astronomy studies, in the current situation. “Not only has this discovery challenged our understanding of the origins of GRBs, (but) it also requires us to consider a new model of how some GRBs form.”

Zhang’s team believes that the unique nature of the explosion may have been caused by a possible collision between a neutron star and a white dwarf, or the size of Earth. The remnants that appear when low-mass stars die.

The event also helped answer some questions about the composition of the heaviest elements in the universe.

said Jillian Rastingad, PhD student in astronomy at Northwestern and first author of ONE natural astronomy studies. “But kilonovae are very hard to notice and they fade very quickly. Now, we know we can also use some long gamma-ray bursts to look for more kilonovae.”

The James Webb Space Telescope will enable astronomers to look for emissions from kilonovas using spectroscopy, or measuring the different wavelengths of light.

“Unfortunately, even the best ground-based telescopes are not sensitive enough to perform spectroscopy,” Rastingad said. “Using[the Webb telescope]we were able to obtain a spectrum from a kilonova. These spectral lines provide direct evidence of your detection of the heaviest elements.”