### Gamma ray astronomy

Gamma rays have the shortest wavelengths. Special telescopes in orbit around Earth, such as the National Aeronautics and Space Administration’s (NASA’s) Compton Gamma-Ray Observatory, gather gamma rays before Earth’s atmosphere absorbs them. X rays, the next shortest wavelengths, also must be observed from space. NASA’s Chandra X-Ray Observatory (CXO) is a school-bus-sized spacecraft that began studying X rays from orbit in 1999. See also Gamma-Ray Astronomy; X-Ray Astronomy.