Curium is a highly radioactive, synthetic element that is produced by bombarding plutonium with alpha particles. It was first produced in 1944 by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso. Curium has a number of isotopes, but curium-242 is the most stable and has a half-life of 163 days. Due to its high radioactivity, curium is both dangerous and useful. It is used in new sources of electricity called radioisotope thermoelectric generators, which are used in some types of space probes, and it has important applications in nuclear physics research. Curium is a rare element and is not found naturally on Earth.