A supernova ‘destroyed’ part of Earth’s ozone for a few minutes in 2022
On October 9, 2022, telescopes in space picked up a beam of high-energy photons hurtling through the cosmos toward Earth, evidence of a supernova that exploded 1.9 billion light-years away. Such events are known as gamma-ray bursts, and astronomers who have continued to study them said this was the cause “the brightest of all time.”
Now a team of scientists has found that this eruption caused a measurable change in the number of ionized particles found in Earth’s upper atmosphere, including ozone molecules, which easily absorb harmful solar radiation.
“The ozone was partially depleted and temporarily destroyed,” said Pietro Ubertini, an astronomer at the National Institute of Astrophysics in Rome who was involved in discovering the atmospheric event. The effect was only noticeable for a few minutes before the ozone repaired itself, so it was “nothing serious,” said Dr. Ubertini. But if the supernova had happened closer to us, he said, “it would be a catastrophe.”
The discovery, reported on Tuesday in a paper published in the journal Nature Communications, shows how even explosions that occur far from our solar system can affect the atmosphere, which can be used as a giant detector for extreme cosmic phenomena.
Most of the ozone in the atmosphere is concentrated in a thin layer of the stratosphere, about 10 to 25 miles above the Earth’s surface. It was in this region that researchers discovered a hole in the ozone layer over Antarctica, largely due to the use of chemicals called chlorofluorocarbons, once found in aerosol cans and plastic foam. The ozone layer absorbs most of our sun’s ultraviolet radiation, which can cause sunburn, skin cancer and damage to crops.
Simulations have shown it that a burst of gamma rays in our Milky Way could wipe out the ozone layer in the stratosphere for years, long enough to cause widespread extinction.
Ozone also exists in lower concentrations higher up in the ionosphere, a part of the atmosphere that extends from 60 to 500 kilometers altitude. At those altitudes it has some protective effect, but much less than at lower altitudes.
To study the effects of last year’s gamma-ray burst on Earth, Dr. Ubertini and his colleagues looked for signals at the top of the ionosphere using data from the China Seismo-Electromagnetic Satellite, an orbiter designed to study changes in the atmosphere during earthquakes.
They identified a sharp jump in the electric field at the top of the ionosphere, which they correlated with the gamma-ray burst signal measured by the European Space Agency’s International Gamma-Ray Astrophysics Laboratory, a mission launched in 2002 to observe radiation from distant celestial bodies to take. objects.
The researchers found that the electric field increased by a factor of 60 when gamma rays ionized ozone and nitrogen molecules high in the atmosphere (essentially knocking away electrons). Once ionized, the molecule can no longer absorb any ultraviolet radiation, temporarily exposing the Earth to more harmful solar rays.
There have been gamma-ray bursts known to ionize molecules at the bottom of the ionosphere, up to about 350 kilometers above the Earth’s surface. But this is the first time scientists have proven that cosmic explosions like this can affect the entire ionosphere, said Laura Hayes, a solar physicist at the European Space Agency who was not involved in the study.
It is unusual for distant cosmic phenomena to cause such large atmospheric disturbances, added Dr. Hayes added. “Fortunately for us, this gamma-ray burst was extremely distant, making its effects a scientific curiosity rather than a threat,” she wrote in an email.
According to Dr. Ubertini, if the gamma-ray burst had been a million times larger, it could have ionized enough ozone to weaken the protective barrier for days or months.
But the chance of that happening is small, he says. Eruptions as powerful as last year’s are rare, occurring only once every 10,000 years. And because the gamma rays flow like jets from supernovae, they also have to be oriented in exactly the right direction to hit Earth.
Still, it’s important to know how the ionosphere responds to cosmic phenomena for threats closer to home. “It helps us measure the recovery time after significant ionization, especially in scenarios with intense solar flares from our Sun,” said Dr. Hayes.
The good news is that the ozone repairs itself: eventually the released electrons are recaptured by ionized molecules in the air. In this case, part of the shield that protects Earth from the formidable dangers of space was restored, protecting the planet and its inhabitants for a while longer from the deadly radiation that the Sun would otherwise send our way.