To observe gamma rays from space, specialized telescopes are necessary since gamma rays are absorbed by the Earth's atmosphere. The most well-known gamma-ray telescopes are the Fermi Gamma-ray Space Telescope and the High Energy Stereoscopic System (H.E.S.S.). These telescopes use different techniques to detect gamma rays, including pair production, where a gamma ray interacts with matter to produce an electron-positron pair, and Compton scattering, where a gamma ray interacts with an electron to produce a lower-energy photon.