On October 9, 2022, for 7 minutes, high-energy photons from a giant explosion 1.9 billion light-years away shook the Earth’s atmosphere. Astronomers believe that the source of the phenomenon was the explosion of a supernova, which resulted in the creation of a black hole. This event, called a Gamma Ray Burst (GRB), was 70 times brighter than the previous record holder and was named by researchers BOAT (short for the brightest of all time). In addition to the light show, this explosion also ionized atoms in the upper atmosphere. If a similar explosion occurred closer, it could potentially harm life on Earth.
The results and description of the research were published in the journal “Nature Communications” (DOI: 10.1038/s41467-023-42551-5).
GRB 221009A
A powerful burst of gamma rays produced by a huge cosmic explosion about two billion light-years away. It reached Earth on October 9, 2022. It lasted just seven minutes, but its glow was visible to astronomers for the next several hours. This explosion affected the ionosphere, which extends at altitudes of 50 to 1,000 kilometers.
Astronomers aren’t entirely sure what causes GRBs. These types of explosions shine as brightly as a bright star in the Milky Way, even though they are billions of times more distant. To throw so much energy across billions of light years, GRBs must be really powerful.
Astronomers believe that some of these explosions may come from supernovae, i.e. exploding stars that have come to an end and collapsed into a neutron star or black hole. Scientists like to emphasize the enormity of such explosions and often compare them to the Sun. According to this, a typical GRB releases as much energy in a few seconds as the Sun releases in its entire 10 billion-year lifespan.
But even by the standards adopted for GRB, this event last October was still exceptional. It launched automated instruments that normally study solar flares. It disrupted long-wave radio communications in the lower ionosphere. They will also affect the upper ionosphere, showing that an explosion more than 2 billion light-years away can affect this layer of the atmosphere.
The impact of the explosion on the Earth’s atmosphere
The disturbance in the ionosphere following this massive explosion was detected immediately, but its scale only became clear when researchers began to analyze the data collected.
GRB 221009A was detected by observatories in space. One of them was the Chinese-Italian CSES satellite (China Seismo-Electromagnetic Satellite) equipped with an electric field detector. It orbits at an altitude of approximately 500 kilometers above the Earth. This small satellite was sent into space in 2018 to study the effects of seismic and volcanic activity and solar flares on the ionosphere.
CSES was in the right place at the right time. It recorded a spike in the electric field in the region of the ionosphere it was traveling through, which may have been caused by the sudden increase in ionization caused by the GRB. To rule out other causes, such as solar flares, the team modeled the effect of a sudden burst of gamma rays on the upper atmosphere. This agreed with the size of the electric field pulse and the time delay between GRB 221009A and the pulse. “This is the first time we have been able to observe such a change in the upper part of the ionosphere,” said Mirko Piersanti from the University of L’Aquila in Italy.
In turn, observations conducted by ESA’s International Gamma-Ray Astrophysics Laboratory (Integral) revealed that within 800 seconds of the flare, it changed the electric fields of the ionosphere down to the layers closest to the planet.
The burst was also picked up by the SuperSID instrument at the Dunsink Observatory in Ireland. It is a simple antenna tuned to receive very low frequency (VLT) radio signals of the order of 3–30 kHz. SuperSID can analyze changes in the shape and strength of passing VLF signals to gather information about the state of the lower ionosphere.
Laura Hayes, analyzing data from SuperSID on October 9, 2022, noticed a sudden jump in VLF signal strength when GRB 221009A occurred. The spike was roughly equivalent in size to a small or medium solar flare. The data collected indicated that photons from the burst reached altitudes of 60 kilometers above the Earth’s surface and ionized more molecules in the air. Previous GRB recordings and the VLF surge they caused occurred at night and were not disturbed by solar activity. But GRB 221009A was captured in the middle of the day.
– We were surprised that it was so big. He even beat the Sun, Hayes said. “We can basically say that the ionosphere has ‘moved’ to lower altitudes, and we detected this by the reflection of radio waves along the ionosphere,” she added.
Potential threat
Scientists have long wondered what would happen if a GRB of similar strength exploded in a nearby galaxy or even the Milky Way. If a GRB that was created in an explosion about two billion light-years away could affect our entire ionosphere in this way, then one that was closer to us could have very serious consequences for us.
“It would destroy the ozone layer, which protects living organisms from the sun’s harmful ultraviolet radiation,” Piersanti admitted.
The ozone layer is composed of three-atomic oxygen molecules. It protects us against harmful ultraviolet radiation, which can cause cancer and damage genetic material. Ozone is born as a result of the interaction of air and sunlight. It is formed naturally in the stratosphere at altitudes of 15 to 35 kilometers.
Scientists estimate that an intense blast of gamma rays from a nearby GRB would produce nitrogen oxides, which destroy ozone faster than it can regenerate. Piersanti estimated that it could take up to a decade for the ozone layer to return to its pre-damage state. During this time, the models indicated, plants and animals could suffer significant DNA damage from increased levels of ultraviolet radiation.
At least one GRB reaches Earth every day. However, it is estimated that a GRB as strong as BOAT occurs once every 10,000. years.
2023-11-16 14:35:10
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