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High Altitude Water Cherenkov Observatory (HAWC) in Mexico. Photo: Jordan A. Goodman
Recent research published on August 3rd in the journal Physical Review Letters has revealed that sunlight from the Sun can possess much higher energy levels than previously thought. Employing highly sophisticated astronomical instruments, a team of researchers identified the most energetic light ever detected from the Sun, reaching nearly 10 trillion electron volts.
This exceptionally intense light takes the form of gamma rays, carrying the highest energy among any type of electromagnetic wave on the spectrum. The scientists discovered that the Sun emits more gamma rays than they initially anticipated.
“Despite being the closest and most familiar star to us, the Sun still holds many surprises. The new observation is very intriguing as the research team has demonstrated that the Sun emits high-energy gamma rays,” commented Brian Fields, an astrophysicist at the University of Illinois, who was not involved in the study.
To measure the Sun’s light, the research team utilized the High Altitude Water Cherenkov Observatory (HAWC), consisting of 300 tanks, each filled with 200 tons of water. Situated between the dormant peaks of the Sierra Negra volcano in Mexico, this observatory detects signals of energy from gamma and cosmic rays, even when their light doesn’t reach Earth’s surface.
When gamma rays collide with the upper atmosphere, they produce a cascade of atomic particles, leaving traces that HAWC can detect. From 2015 to 2021, the researchers collected data from such events and recorded solar gamma radiation exceeding the threshold of 1 trillion electron volts of energy. “After examining six years’ worth of data, this gamma ray surprised us by appearing for the first time. The Sun cannot emit light at such energy levels,” shared Mehr Un Nisa, a postdoctoral researcher at the University of Michigan.
HAWC enabled scientists to determine that the Sun’s gamma radiation is 10 times stronger than previously calculated. However, they are yet uncertain about the mechanism behind the Sun’s production of such high-energy gamma rays and why they are so abundant.