Astronomers have discovered the most energetic light beams ever observed emanating from the sun, a discovery that raises new concerns about how such radiation is emitted from the sun’s atmosphere.
Since the 1990s, scientists have observed that the sun discharges numerous types of high-energy radiation, including gamma rays, as predicted by theory.
Nevertheless, a new study based on six years of data and published Thursday in the journal Physical Review Letters reveals that the sun emits significantly more gamma rays than previously believed.
“The sun is more surprising than we knew. We thought we had this star figured out, but that’s not the case,” said Michigan State University (MSU) co-author Mehr Un Nisa.
Even though this type of radiation does not reach the surface of the Earth, it tends to leave “telltale signatures” in the atmosphere.
Scientists made the observation using the High-Altitude Water Cherenkov Observatory (HAWC) atop the Sierra Negra volcano near Puebla, Mexico, at an altitude of approximately 4,100 meters (13,500 feet).
The facility is specifically designed to observe gamma rays and cosmic rays generated in the universe’s most extreme environments, such as supernova explosions.
It utilizes a network of 300 large water tanks, each holding approximately 200 metric tons of water, located between two dormant volcano peaks in Mexico.
Years of Data Analysis Pave the Way for In-Depth Study of Solar Gamma Radiation
Since 2015, Dr. Nisa and her team have been analyzing data from such interactions; by 2021, they had accumulated enough data to begin investigating the sun’s gamma radiation with sufficient scrutiny.
The sun emits energy at various wavelengths, with some being more abundant than others.
One of these is visible light, which carries approximately one electron volt of energy.
In comparison, the gamma radiation observed by Dr. Nisa and her team contained approximately 1 tera electron volt (1 TeV).
Not only did this energy level surprise the researchers, but so did the quantity of these rays they detected.
Scientists theorized in the 1990s that the sun could generate gamma rays when cosmic rays from sources such as a black hole or supernova collide with the sun’s protons.
However, it was also hypothesized that these gamma rays would rarely reach Earth. No instruments capable of detecting such high-energy gamma rays existed at the time.
The Fermi Gamma-ray Space Telescope made the first observation of gamma rays with energies exceeding one billion electron volts in 2011.
This telescope’s measurements of the sun’s gamma radiation, however, reached a maximum of approximately 200 billion electron volts.
According to Dr. Nisa, the most recent observation demonstrates for the first time that the energies of the sun’s beams can extend into the TeV range, up to nearly 10 TeV, which may be the limit.
However, scientists are still uncertain as to how these gamma particles attain such high energies.
Also unknown is the function of the sun’s magnetic fields in this phenomenon.