very-high-energy gamma rays

The term very-high-energy gamma rays (VHEGR) is used for gamma rays in the 100 GeV to 100 TeV range of photon energy. Such high-energy photons are detected, typically using detectors aimed at this specific range by detecting the Cherenkov radiation associated with air showers (Cherenkov detectors): the VHEGR-photon interaction with Earth atmosphere produces particles with sufficient kinetic energy to produce lower-frequency Cherenkov radiation as they, in turn, pass through the atmosphere. One reason such gamma rays are of interest is the assumption that they travel very straight, increasing the chances of identifying the source. The creation of VHEGRs is of research interest: one notion is that they can result from a blazar with a jet pointed toward us.

The term VHE is also used more generally for this energy range. Photons beyond 100 TeV are termed ultra-high-energy gamma rays (UHEGR).