Astronomers have unveiled the first gamma-ray maps of the Sun, which detail the ebb and flow of these high-energy photons over nearly a decade of observations. The data raise more questions then they answer. When speedy interstellar protons known as cosmic rays slam into the Sun, they produce gamma rays that can be observed from Earth. By tracking how this gamma ray flux changes with time, researchers hope to better understand how the Sun interacts with its surroundings and how those interactions relate to its ever-changing magnetic engine.
Tim Linden, of The Ohio State University in Columbus, and colleagues analyzed gamma-ray data of the Sun taken by NASA’s Fermi space telescope from 2008 to 2017. This period covered most of the last solar cycle, the latest round of the 11-year oscillation in the Sun’s magnetic activity. They found that the Sun’s poles steadily emitted gamma rays throughout the cycle. But surprisingly, the flux from the solar equator varied dramatically, outshining the poles during the solar minimum in 2009 before going largely quiet in gamma rays for the rest of the cycle.