https://en.wikipedia.org/wiki/Gamma-ray_astronomy
Gamma-ray astronomy is the astronomical observation of gamma rays, the most energetic form of electromagnetic radiation, with photon energies above 100 keV.Radiation below 100 keV is classified as X-rays and is the subject of X-ray astronomy.. In most known cases, gamma rays from solar flares and Earth's atmosphere are generated in the MeV range, but it is now known …