May 30, 2024


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The most powerful space explosion ever revealed a surprising development: ScienceAlert

The most powerful space explosion ever revealed a surprising development: ScienceAlert

In October 2022, surveys began to monitor the sky for explosions in space Like a frog in a sock.

the reason? Something 2.4 billion light-years away unleashed the largest gamma-ray burst ever recorded. The event, GRB 221009A, hit a record high of 18 TeV, and was so powerful that it shook Earth's outer atmosphere.

The event, nicknamed The Boat (for brightest of all), we later determined to be the birth of a black hole as a result of the violent death of a massive star.

Now a new analysis of cutting-edge light has revealed the complexities of this explosion, finding that for all the gamma-ray fury, the boat was actually surprisingly ordinary, something we didn't expect.

“It is no brighter than previous supernovae.” says astrophysicist Peter Blanchard From Northwestern University in the United States.

“It seems fairly natural in the context of other supernovae associated with less energetic gamma-ray bursts (GRBs). You might expect that the same collapsed star that produces very active, bright GRBs would also produce a very active, bright supernova. But it turns out to be the case. “Not so. We have a very luminous GRB, but it's a normal supernova.”

Gamma ray bursts They are the most powerful explosions ever seen in the universe. They are, as their name suggests, bursts of gamma radiation — the most energetic light in the universe — that can explode in 10 seconds with the same energy the Sun emits in 10 billion years.

We know of at least two main events that can create GRBs: the formation of a black hole when a massive star goes supernova, or the supernova accompanying the merger of two neutron stars.

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The types of novae that produce gamma-ray bursts are also thought to be responsible for the production of heavy elements in the universe. The problem is that heavy elements simply did not exist until stars created them.

Stars are made mostly of hydrogen gas, which is abundant in the universe, but they smash atomic nuclei together to form heavier elements. This applies to iron, because the fusion of iron atoms absorbs more energy than it generates.

However, elements heavier than iron can form during the violent throes of a giant cosmic explosion. We have seen it! In the wake of neutron star collisions, scientists have discovered elements that are too heavy to have formed by core fusion.

An artist's concept of GRB 221009A shows jets exploding from a newly formed black hole. (Aaron M. Geller/Northwestern/CIERA/Information Technology, Computing and Data Research Services)

But there is a lot we don't know. If we can narrow down the range of explosions that are most likely to produce these elements, we will have a new tool for understanding not only how the universe makes stuff, but how common such explosions are.

So, naturally, Blanchard and his colleagues wanted to take a look at GRB 221009A to see if there were signs of heavy elements in the light it emits.

But they had to wait. The explosion was so bright that it blinded our instruments.

“The GRB explosion was so bright that it obscured any possible supernova signature in the first weeks and months after the explosion.” Blanchard explains.

“At these times, the so-called afterglow of the GRB looked like the headlights of a car coming straight at you, preventing you from seeing the car itself. So, we had to wait until it had faded significantly to give us a chance to see the supernova.”

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It wasn't until about six months after the explosion was first seen that researchers were able to use the James Webb Space Telescope to look at light at infrared wavelengths. In this way they were able to determine that the supernova itself was relatively normal. The reason it was so bright was likely because the gamma-ray burst was directed directly at Earth.

Next, the researchers combined the James Webb Space Telescope data with radio observations from the Atacama Large Millimeter/submillimeter Array to search for specific wavelength bands consistent with the presence of heavy elements. However, while they found things like calcium and oxygen, which are fairly standard in supernovae, there was no sign of heavy element production.

Now, the rate at which neutron stars merge is not enough to generate the amount of heavy matter we see in the universe. Giant explosions like GRB 221009A were expected to be a contributor, but the lack of heavy elements suggests we were wrong about that.

So we need to look at other potential sources to see if we can identify the culprit, the researchers say.

“We did not see signatures of these heavy elements, which suggests that very energetic gamma-ray bursts like the boat do not produce these elements.” Blanchard says.

“This does not mean that all GRB bursts do not produce them, but it is an essential piece of information as we continue to understand where these heavy elements come from. Future observations with JWST will determine whether BOAT's 'natural' cousins ​​produce these elements.”

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The results have been published in Nature astronomy.