Scientists puzzled by super-bright light from the sun Premium

After observing gamma rays coming from the sun for six years, researchers at the HAWC observatory in Mexico have found an excess of very high-energy gamma rays emerging as a result of the interaction between cosmic rays and the sun’s magnetic field. Researchers currently don’t have an explanation for this excess.

A stream of energetic particles, called cosmic rays, constantly bombards earth from space. It is kept from reaching the ground by earth’s atmosphere and magnetic field. Scientists know that cosmic rays come from the centres of large galaxies and from the explosive deaths of massive stars, or supernovae, based on detectors fit on satellites.

Scientists have also detected cosmic rays coming from the direction of the sun, which is because the star’s magnetic field has deflected them towards earth. Sometimes, particles in the cosmic rays interact with the sun’s atmosphere to produce gamma rays, which scientists study as solar gamma rays.

As products of the solar magnetic field, the composition of the solar atmosphere, and the composition of cosmic rays, scientists can deduce much about these three things by studying the solar gamma rays themselves. Now, a new measurement has indicated to scientists that they may be missing something in this relationship.

Researchers at the High-Altitude Water Cherenkov (HAWC) Observatory, in Puebla, Mexico, reported on August 3 in the journal Physical Review Letters that HAWC had detected TeV-energy gamma rays from the sun. TeV stands for tera-electron-volt, or 1 trillion eV, a very high amount of energy for particles. This, the paper’s authors write, is the first time such energetic gamma rays have been detected from the sun.

HAWC also found more such high-energy gamma rays than expected.

Existing models of the sun’s magnetic field and atmosphere can’t account for this ‘excess’ energy and brightness, and scientists will need to figure out why.

“Most ongoing research is focused on trying to correctly model how the cosmic rays interact in the sun’s atmosphere,” Michigan State University postdoctoral research associate and a corresponding author of the new study Mehr Un Nisa told this writer in an email. “The cosmic-ray composition is relatively well-understood. However, the solar magnetic fields at various distances from the sun’s surface and their evolution with time is a complicated problem.”