February 2, 2023

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A powerful cosmic flash turns 20 years of astronomical knowledge upside down

A powerful cosmic flash turns 20 years of astronomical knowledge upside down

“This is really a very special measurement,” says astronomer Ralph Wijers of the University of Amsterdam, who was not involved in the study himself.

Even “GRB 211211A,” as it’s called, was the realm of gamma-ray bursts in the clear. They come in two types: a short one, lasting up to two seconds. And long ones that can last for hours. This shorter variant results from the collision of two celestial bodies: neutron stars, for example, or a neutron star and a black hole. The long form sometimes occurs when a very massive star dies in a supernova explosion.

frontier cases

“We expected that there would be borderline cases,” says Wijers. It seemed only a matter of time before one would find a gamma-ray burst caused by the collision of two celestial bodies lasting a little longer than two seconds.

But GRB 211211A exceeds this expectation. It is almost certainly caused by the collision of two celestial bodies and lasts up to about a minute. “This is not only a little over the edge, but really — bam — in the middle of long gamma-ray bursts,” Wiggers says.

And this is strange. Because such a collision itself takes place within a few milliseconds. “Computer models show that you can really extend the flash to seconds, but it’s a mystery to me how you can keep it going for a full minute with the massive amount of energy that a gamma-ray burst releases,” he says. “It gives us food for thought. You have to be very creative to be able to explain that.”

extremely rare

Gamma-ray bursts – even those that fit neatly into your current straitjacket – are extremely rare. “In every galaxy, it occurs at a rate of about once every million years,” Wiggers says.

GRB 211211A coincidentally happened to be in another galaxy, 1.1 billion light-years away from Earth. The last time a gamma ray burst in our Milky Way was in 2005. “It still happens at a great distance – almost from here to the center of the Milky Way – but with radio receivers you can still measure the effect of measuring the radiation emitted from this The flashes on Earth’s atmosphere,” says Wijers. “These kinds of flashes are really incredibly powerful.”

A gamma ray burst is sometimes referred to as suspect In connection with the large-scale extinction of a large number of animal species on Earth. It happened about 450 million years ago, one of the five extinction waves that our planet has had to deal with in its history, the so-called Late Ordovician mass extinction. The gamma ray burst may have caused that wave indirectly.

“But in terms of the danger from the sky, I wouldn’t take gamma-ray bursts seriously, they’re far too rare for that,” says Wijers. “We’d better keep a close eye on all the space rocks.”

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