On October 9, 2022, at 3:21 p.m. (Spanish peninsular time), several observation satellites in Earth orbit, from both NASA and the European Space Agency (ESA), detected a powerful emission of high-energy radiation, in the form of gamma rays, that came from a very distant galaxy, located 2 billion light-years away, probably caused by the death of a massive star.
The emission was the most intense ever received and the event that generated it released, in just 800 seconds, hundreds of times the energy that the Sun will emit in its entire life (10 billion d ‘years). Now, a study shows that its arrival caused disturbances in the upper layer of the Earth’s ionosphere, a previously unheard of event, and points to the possibility that a similar event, but much closer, could have consequences for life in the earth.
Gamma-ray bursts are sudden, very short-lived phenomena (from seconds to a few minutes) in which an enormous amount of high-energy light is emitted into space. Because, fortunately for life on Earth, this radiation is filtered out by the atmosphere, the main gamma-ray detectors are in Earth orbit.
The burst detected in October 2022 was given the scientific name GRB 221009A, but is informally known as BOAT (the largest of all time). It exceeds at least 10 times the power of the most intense that has been known so far and was so powerful that it came to saturate the detection capacity of most instruments designed specifically for the study of this kind of phenomena. The arrival of radiation took place over India and illuminated large areas of Europe, Africa, Asia and part of Australia.
At first, it was thought that the origin was in our galaxy, but observations with several satellites and also with the European Southern Observatory’s VLT telescope confirmed that the source was in a very distant galaxy, 2,000 millions of light years away. Later, observations with the Gran Canaria Telescope confirmed the presence, in this galaxy, of a luminous residue compatible with the explosion of a very massive star.
According to the ESA, the arrival on Earth of the radiation that comes from such an extreme phenomenon could take place statistically every 10,000 years, so, as stated by Alicia Rouco Escorial, specialist in gamma ray bursts from the agency, the scientists were “very lucky to be able to capture it”.
During the 800 seconds that the phenomenon lasted, the beam of radiation that reached our planet caused several effects, including the activation of radiation detectors in India and, more significantly, disturbances in the ionosphere of the Earth, region of the Earth’s atmosphere between 50 and 950 kilometers high.
The Earth’s ionosphere is mainly composed of electrically charged particles, such as electrons and ions, which are generated due to the incidence of solar radiation on air molecules. It is an essential layer for the propagation of radio waves.
Until now, the detected bursts of gamma rays, despite being enormously energetic in terms of origin, had reached the Earth sufficiently weakened due to the distance traveled. Only a few had managed to affect the ionosphere, and even then only partially.
Nevertheless, in the recently published study, the researchers present the detection of strong disturbances, due to the BOAT outbreak, also in the highest layer of the ionosphere. The disturbances affected the bouncing of very low-frequency radio waves between the Earth’s surface and the lower part of the ionosphere. Scientific analysis revealed an increase in the amount of ionized (electrically charged) particles in this region of the atmosphere. As Laura Hayes, an ESA researcher specializing in solar physics, comments, “essentially, we can say that the ionosphere moved downwards”.
