Gamma radiation (sometimes called
gamma ray), denoted by the lower-case Greek letter
gamma (
γ), is extremely high-frequency
electromagnetic radiation and therefore consists of high-energy
photons.
Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by
radium. In 1903,
Ernest Rutherford named this radiation
gamma rays. Rutherford had previously discovered two other types of
radioactive decay, which he named
alpha and
beta rays.