Einsteinium is a highly radioactive synthetic element produced by bombarding plutonium with neutrons. The einsteinium-253 isotope was discovered in 1952 when scientists were examining the debris from the first hydrogen bomb test. It was synthesized in 1961 and used to produce mendelevium. Additional production took place at Oak Ridge's High Flux Isotope Reactor. The homologue of einsteinium is holmium.