2023-08-05 19:10:00
The star closest to us, the sun, continues to amaze researchers with its untold mysteries. A recent discovery once once more upsets our established knowledge of this radiant star.
More Un Nisa, a postdoctoral researcher at Michigan State University, played a crucial role in this celestial investigation. In his words, “the sun is more surprising than we thought“. And for good reason, she and her international team have discovered the highest energy light ever observed emanating from the sun: gamma radiation. But that’s not all, this light is also surprisingly brightwhich means there are more of them than scientists had expected.
Observation with the HAWC
Despite the immense energy of this light, it does not reach the surface of the Earth. However, these gamma rays leave traces that Nisa and his colleagues were able to detect thanks to theCherenkov High Altitude Water Observatory (HAWK). The latter, which operates continuously unlike other observatories, was essential in this discovery. The HAWC observes the consequences of the collisions of gamma rays with air in the atmosphere, creating what are called “atmospheric sheaves“.
Michigan State University postdoctoral fellow Mehr Un Nisa at the Cherenkov High Altitude Water Observatory. Credit: Courtesy of Mehr Un Nisa
The HAWC does not look like a typical telescope. Instead of a tube fitted with glass lenses, the HAWC uses a network of 300 large water reservoirs, nestled between two peaks of dormant volcanoes in Mexico. When the spray particles interact with the water in the HAWC reservoirs, they create what is called the radiation Cherenkovwhich the observatory’s instruments can detect.
Six-year data
Data collection began in 2015, and by 2021 the team had accumulated enough data to begin examining the sun’s gamma rays with sufficient precision. That’s when they discovered an excess of gamma rays, leaving Nisa and her team stunned.
“After looking at six years of data, an excess of gamma rays appeared“, said the researcher. “When we first saw it, we thought we had definitely made a mistake. The sun cannot be as bright at these energies.
What an excess of solar gamma rays looks like for the High-Altitude Water Cherenkov Observatory Collaboration, which includes researchers from Michigan State University. Credit: Courtesy of HAWC Collaboration
A story in progress
The gamma rays observed by Nisa and his colleagues reached approximately 1 tera electron-volt, or one trillion electron-volts. The level of energy was certainly surprising, but what was even more surprising was that they saw so much.
The Collaboration HAWCwhich includes more than 30 institutions across North America, Europe and Asia, has thus shown that the energies of the sun’s rays extend into the tera-electron-volt range, up to nearly 10 tera electron volts.
New questions emerge
Currently, this discovery raises more questions than it answers. Solar scientists will now have to look at how these gamma rays reach such high energies and what role the sun’s magnetic fields play in this phenomenon.
It reminds us that there is always something missing or misunderstood in our understanding of our nearest and dearest star.
Synthetic
The study of the sun continues to amaze us and push us to push the limits of our knowledge. The latest discoveries relating to gamma radiation from the sun force us to re-evaluate our understanding of this star. This new discovery, although it raises many questions, makes a valuable contribution to our knowledge of our galaxy at the highest energies.
For a better understanding
What are gamma rays?
Gamma rays are a very high-energy form of light, which sits at the top of the electromagnetic spectrum.
How are gamma rays detected?
Although high-energy gamma rays do not reach the Earth’s surface, they leave characteristic signatures that can be detected by specialized instruments, such as those used by the HAWC.
What is the HAWC?
The HAWC is the High Altitude Water Observatory at Cherenkov. It is located between two peaks of dormant volcanoes in Mexico and uses a network of large water reservoirs to observe gamma rays.
What is the significance of this discovery?
This discovery challenges our current understanding of the sun and opens up new avenues of research to understand how these high-energy gamma rays are produced.
Main image caption: Michigan State University is part of the collaboration using the Cherenkov High Altitude Water Observatory in Mexico to study high-energy phenomena in our galaxy. Credit: Jordan A. Goodman/Wikimedia Commons
Nisa, soon to join the faculty at MSU, is the corresponding author of a new paper published in the journal Physical Review Letterswhich describes the discovery of the most energetic light ever observed from the sun.
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