Simplify the following text for a Grade 6 native English-speaking person.
Original: Paul Villard , a French chemist and physicist , discovered gamma radiation in 1900 , while studying radiation emitted from radium . Alpha and beta `` rays '' had already been separated and named by the work of Ernest Rutherford in 1899 , and in 1903 Rutherford named Villard 's distinct new radiation `` gamma rays . ''
Simplified: They were discovered in 1900 by Paul Villard , and named in 1903 by Ernest Rutherford .