A 50-second gamma ray burst detected on Earth challenges understanding of how the Universe works

A 50-second gamma-ray burst (GRB) that swept through the Solar System has challenged the origin of such bursts – the brightest and most energetic explosions since the Big Bang.

It had been thought that such long-lasting GRBs only come from the collapse of massive stars that can be tens to hundreds of times the mass of our Sun. Enormous shock waves created during the collapse of a star cause the outer part of the star to explode in a supernova, and can leave behind a black hole.

GRBs of less than two seconds are considered short and are thought to be caused by the merger of a neutron star with another compact object – either another neutron star or a black hole. The resulting explosion is called a kilonova, and is considerably smaller than a supernova.

But a team of astrophysicists has just published research in which they say the 50-second GRB, detected in December 2021, was the result of merging neutron stars, despite the long duration of the burst.

READ MORE:
* Stellar explosion could explain 13-billion-year-old Milky Way mystery
* Scientists a step closer to solving space mystery after uncovering signal pattern
* Far out: Astronomers discover the most distant star ever seen

Researchers, led by a team from Northwestern University in the US, decided to study the GRB, named GRB211211A, because it was a relatively close 1.1 billion light years away. They used a multitude of telescopes that could observe across the electromagnetic spectrum.

After examining near-infrared images, the team spotted an incredibly faint object that quickly faded, Northwestern said.

Two neutron stars begin to merge in this illustration, blasting a jet of high-speed particles and producing a cloud of debris.

A. Simonnet (Sonoma State University) and NASA’s Goddard Space Flight Center

Two neutron stars begin to merge in this illustration, blasting a jet of high-speed particles and producing a cloud of debris.

Supernovae don’t fade as quickly and are much brighter, so the team realized they had found something unexpected that was previously believed impossible. They found the telltale signature of a kilonova – the result of merging neutron stars.

Because neutron stars were clean, compact objects, researchers previously believed neutron stars did not contain enough material to power a long-duration GRB, Northwestern said.

“When you put two neutron stars together, there’s not really much mass there,” Northwestern assistant professor of physics and astronomy Wen-fai Fong said. A little bit of mass accreted, powering a very short-duration burst.

“This unexpected finding not only represents a major shift in our understanding, but also excitingly opens up a new window for discovery.”

A view of GRB 211211A's location, circled in red, captured using three filters on Hubble's Wide Field Camera 3.

NASA, ESA, Rastinejad et al. (2022), Troja et al. (2022), and Gladys Kober (Catholic Univ. of America)

A view of GRB 211211A’s location, circled in red, captured using three filters on Hubble’s Wide Field Camera 3.

The kilonova wasn’t the only strange part of the study, Northwestern said.

The GRB’s host galaxy was also curious. Named SDSS J140910.47+275320.8, the host galaxy was young and star-forming, almost exactly opposite of the only other known local universe host of a neutron star merger event.

“This galaxy is fairly young, actively star forming and not actually that massive. In fact, it looks more similar to short GRB hosts seen deeper in the universe,” astronomy PhD student Anya Nugent said.

“I think it changes our view of the types of galaxies we should watch when we’re searching for nearby kilonovae.”

NASA/Swift/Cruz deWilde

Astronomers think GRB 221009A represents the birth of a new black hole formed within the heart of a collapsing star. As illustrated here, the black hole drives powerful jets of particles traveling near the speed of light.

It also changed how astrophysicists might approach the search for heavy elements, such as platinum and gold, Northwestern said.

Astrophysicists thought supernova explosions and neutron star mergers produced the heaviest elements, but clear signatures of their creation were rarely observed.

“Kilonovae are powered by the radioactive decay of some of the heaviest elements in the universe,” PhD student Jillian Rastinejad, who led the study, said.

“But kilonovae are very hard to observe and fade very quickly. Now, we know we can also use some long gamma-ray bursts to look for more kilonovae.”

The research has been published in the journal Nature.

Afterglow of GRB 221009A about an hour after it was first detected, captured by the X-ray telescope on Nasa's Swift Observatory

NASA/Swift/A. Beardmore (University of Leicester)

Afterglow of GRB 221009A about an hour after it was first detected, captured by the X-ray telescope on Nasa’s Swift Observatory

Meanwhile, another gamma-ray burst – GRB 221009A – has excited astronomers around the world.

That event, in October, was unusually bright and long-lasting. It was detected for more than 10 hours, with telescopes around the world turning towards the site or origin.

The signal had traveled for an estimated 1.9 billion years, and astronomers think it represented the birth of a black hole, formed in the heart of a massive star collapsing under its own weight.

“In these circumstances, a nascent black hole drives powerful jets of particles traveling near the speed of light. The jets pierce through the star, emitting X-rays and gamma rays as they stream into space,” Nasa said.

Leave a Comment