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A gamma-ray burst in a distant galaxy disrupted the Earth’s upper atmosphere

WASHINGTON: About two billion years ago, in a galaxy far beyond our Milky Way, a large star disappeared in a massive explosion called a supernova that triggered a huge burst of gamma rays, which contain the most energy of all waves of the electromagnetic spectrum. .

These waves traveled through the cosmos and finally reached Earth last year. This gamma-ray burst, researchers said Tuesday, caused a significant disruption of Earth’s ionosphere, a layer of the planet’s upper atmosphere that contains electrically charged gases called plasma.

Scientists had previously determined that it was the most powerful explosion of its type ever detected.

The ionosphere is located approximately 30 to 600 miles (50 to 950 km) above the Earth’s surface, extending to the far reaches of space. It helps form the boundary between the vacuum of space and the lower atmosphere inhabited by humans and other inhabitants of Earth.

Gamma rays from the explosion impacted the Earth’s atmosphere for approximately 13 minutes on October 9, 2022. They were detected by the Integral space observatory (International Gamma-ray Astrophysics Laboratory) of the European Space Agency and by various satellites in near-Earth orbit.

The gamma rays caused a strong variation in the ionosphere’s electric field, according to Mirko Piersanti, a space weather researcher at the University of L’Aquila in Italy and lead author of the research published in the journal Nature Communications.

“It was similar to what typically happens during a solar flare,” Piersanti said, referring to the sun’s powerful bursts of energy.

But the gamma-ray burst occurred at a great distance – the rays traveling about two billion light years – compared to the relative proximity of the sun, showing how even distant events can influence Earth. A light year is the distance light travels in a year, or 5.9 trillion miles (9.5 trillion kilometers).

Instruments on Earth showed that the gamma rays disrupted the ionosphere for several hours and even triggered lightning detectors in India. The disturbance reached the lowest layers of the ionosphere.

Since the 1960s, scientists have measured gamma-ray bursts – bursts of energy released in supernovas, or the merger of two neutron stars, which are the dense, collapsed cores of massive stars. An explosion as strong as the one detected last year is expected to reach Earth about once every 10,000 years, scientists say.

The ionosphere, which helps protect life on Earth by absorbing the sun’s harmful ultraviolet rays, is very sensitive to changes in magnetic and electrical conditions in space, usually linked to solar activity. It also expands and contracts in response to solar radiation.

Although this gamma-ray burst did not cause deleterious effects on life on Earth, it has been hypothesized that a powerful gamma-ray burst originating from the Milky Way and pointed directly at us could pose a danger – including mass extinctions – by subjecting the Earth’s surface to flooding. harmful ultraviolet rays.

However, “the probability of this happening is really negligible,” said astronomer and study co-author Pietro Ubertini of Italy’s National Institute of Astrophysics.

The effects of this gamma-ray burst were studied with the help of the Chinese Seismo-Electromagnetic Satellite (CSES), also called Zhangheng, a Sino-Italian mission launched in 2018.

“Here we were lucky since we used the power of the EFD (electric field detector) instrument on board the CSES, capable of measuring the electric field with unprecedented resolution,” Piersanti said.

Ubertini said the disturbance in the ionosphere was not seen by anyone on the ground.

“No one detected anything, but we don’t know if it would have been possible to see a visible signal by looking at the sky at the right time,” Ubertini said.

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