2023-08-12 09:00:00
The sun emits much more numerous and powerful gamma rays than initially envisaged by scientists Tristan Bergen 12/08/2023 11:00 7 min
While we thought we knew a ray from our star, scientists have recently discovered that it emits a certain type of very powerful radiation, gamma rays. If it had already been proven that the sun could generate these rays, their exceptional intensity and frequency greatly surprised the researchers.
How are these gamma rays detected?
Our sun is constantly monitored, because its eruptions can, depending on their intensity, have an impact on terrestrial electrical infrastructure. Thus, many observation points are present in the four corners of the globe to observe its evolution, including the observatory HAWC (High-Altitude Water Cherenkov) located in Mexico. It is in this particular observatory that were detected the strongest solar radiation ever measuredgamma rays of more than one teraelectronvolt, i.e. trillion times more energetic than visible light.
This observatory, however, is not built like most telescopes. It is composed of 300 tankseach filled with approximately 200 tons of water and located between two ancient volcanoes at over 4000m altitude. It was designed to observe atmospheric sheaves “, which result from the interactions between cosmic rays and our atmosphere.
They observe the universe from Mexico with a vision of gamma rays #BoletínFCCyT @Conacyt_MX pic.twitter.com/Vhu5irBhnW
— FCCyT (@foroconsultivo) July 20, 2015
These collisions generate particles of lower energy, which themselves create other particles as they descend towards the surface. When all of these particles interact with the water in the HAWC reservoirs, they create Cherenkov radiation, which the observatory’s instruments can detect.
For 6 years, between 2015 and 2021, the scientists in charge of this observatory collected data to discover something amazingthe sun emits much more powerful gamma rays than the models predicted. The researchers first thought it was an error in the data collected, but the results were still irrefutable.
The sun emits far more gamma rays than expected
Solar gamma rays occur when cosmic rays (high energy particles emitted by supernovas or black holes for example) move towards the surface of the sun and are then deflected by its magnetic field. As they move away from the surface of the sun, these interact with gases in the solar atmosphere. to create some kind of radiationgamma rays.
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The sun emits a large amount of radiation, some being more abundant than others. In the 1990s, scientists speculated that the Sun could also produce gamma rays but it was however unlikely that they would reach the Earth although the lack of instruments at that time had not made it possible to refute this hypothesis. It wasn’t until 2011 that NASA detected the first high-energy gamma rays.detections which then multiplied in the following years, in particular with the commissioning of the HAWC.
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With the multiplication of the detection of this type of radiation, the scientists realized that these were about 7 times more numerous than they expected but also much more powerful. Some gamma rays have indeed reached close to 10 TeVan exceptional energy when compared to the energy of visible light which is about 1eV. If this radiation is the powerful ever detected coming from the sun, it is however not the most intense to have been observed in space sincea radiation of 450Tev was measured a few years ago, coming from the Crab Nebula.
A still unexplained origin
While this new discovery about our sun reminds us that space still has many surprises in store for us and that even the familiar sun also hides secrets, it also raises new questions. How can the sun generate such intense radiation?
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Scientists have noticed that these gamma ray fluxes are inversely proportional to the level of solar activity. These are more intense during solar minimums and weaker during maximums. Such variation suggests that the magnetic fields of the sun are probably not unrelated to the phenomenonbeing responsible for the solar cycle and the solar flares that characterize it.
However, the exact role of magnetic fields and how they interact with cosmic rays to produce such a powerful gamma-ray flux remains to be elucidated and several hypotheses have been proposed by the scientific community. For some, the solar magnetic fields could, for example, act as a electron accelerator cosmic rays, producing much more powerful gamma radiation than previously thought.
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In any case, how these are produced still remains a mystery that many specialists are looking into. Before seeing more clearly and understanding this phenomenon, there is however no need to worry, these rays being harmless for earthlings. Nevertheless, they may have significant implications for the future of space travel and a reassessment of the dangers to which astronauts are subjected on long flights will likely be necessary.
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