The gamma-ray burst, which has become the brightest ever recorded, could provide important information about the cause of mass extinctions in Earth’s history.
Last Thursday something wonderful happened. Space telescope International Gamma-ray Laboratory for Astrophysics (Integrated) Capture a special signal. It turned out to be an extremely bright and long-lasting gamma-ray burst (GRB), which was named GRB 221009A. This gamma-ray burst is unlike any other we have seen so far, the researchers wrote in the journal Nature Communications. “This was probably the brightest thing we have ever observed,” researcher Mirko Piersanti said.
Gamma explosions are the most energetic events in the universe. However, it remains invisible to the human eye. They appear as intense bursts of high-energy gamma rays, lasting from a few milliseconds to several minutes. Although all known gamma-ray bursts originate outside our Milky Way Galaxy, they are bright enough to be observed from billions of light-years away. Scientists are still studying the exact causes of these short-lived events, but we know that they can be caused, for example, by the collision of two neutron stars or the collapse of a massive star. The majority of gamma-ray bursts occur when the core of a star larger than our Sun collapses into a black hole. These events can be incredibly bright, releasing in just a few minutes as much energy as our Sun produces in its entire lifetime.
Scientists have been measuring gamma-ray bursts since the 1960s. But GRB 221009A seems to be quite the odd one out. “It’s the strongest force ever measured,” says co-author Pietro Ubertini. The flash was so powerful that a previous similar flash in the archive was ten times weaker. Statistically speaking, a gamma-ray burst as powerful as GRB 221009A only occurs once every 10,000 years (!).
And at the same time on the ground
The gamma ray burst certainly did not go unnoticed. This lasted seven minutes, then remained detectable for more than 10 hours. During the 800 seconds that the gamma rays hit our planet, the explosion was powerful enough to set off lightning detectors in India. In Germany, signals were received that the Earth’s ionosphere (see box) had been disturbed for several hours.
More about the ionosphere
The ionosphere is the part of Earth’s upper atmosphere that consists of electrically charged gases, also called plasma. This layer extends from about 50 kilometers to 950 kilometers above the Earth’s surface. Scientists refer to the part above 350 kilometers as the upper ionosphere and the part below as the lower ionosphere.
The researchers made this discovery after studying the data received from the spacecraft China electromagnetic seismic satellite (CSES) has bowed. Launched in 2018, CSES closely monitors the upper reaches of the ionosphere, recording changes in its electromagnetic behavior.
The team realized that if GRB 221009A’s explosions caused a disturbance, CSES would likely detect it. And it turns out that this is true. The effect was clear and strong. For the first time, researchers observed severe disturbance in the form of a strong variation in the electric field at the top of the ionosphere. This is special. Although we know that gamma-ray bursts affect the Earth’s lower ionosphere, their effects on the upper ionosphere have not been observed before. “It’s amazing,” exclaims researcher Eric Kolkers. “We can observe events deep in space, but at the same time they affect Earth.”
2 billion light-years away
The fact that Earth has experienced the effects of GRB 221009A firsthand is truly impressive. This gamma-ray burst occurred in a galaxy about two billion light-years away, about two billion years ago. However, the flash had enough energy to impact the ground. Normally, similar disturbances in the ionosphere are caused by energetic particle events on the Sun. But in this case, the culprit was a distant exploding star. GRB 221009A activated instruments normally used to study massive explosions in the Sun’s atmosphere known as solar flares. “It is striking that this disturbance also affected the lower layers of the Earth’s ionosphere, which is only a few tens of kilometers above the surface of our planet,” said researcher Laura Hayes. “It left an impression similar to that of a large solar flare.”
A star being so distant, at least two billion light-years away, can make this a bit annoying as well. It reinforces the idea that a supernova in our galaxy could have more serious consequences. “There is a lot of discussion about what a gamma-ray burst could accomplish in our galaxy,” Piersanti says. In the worst case, such an explosion would not only affect the ionosphere, but could also damage the ozone layer. This would lead to dangerous ultraviolet rays from the sun reaching the Earth’s surface.
A record gamma-ray burst may provide important information about mass extinctions in Earth’s history. For example, it is thought that one or more gamma-ray bursts in our galaxy could be responsible for some past extinction events. However, the researchers stress that to test this hypothesis, we need significantly more data.
Now that they knew exactly where to look, the team began analyzing more CSES data. They would then like to compare it with other gamma-ray bursts observed by Integral. This ensures that we can continue to discover how Earth is connected to the most distant parts of the universe.
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