Plutonium naturally forms in the heart of a star undergoing supernova, along with virtually all of the heavy elements in the universe. It is not found on Earth due to its instability. The most stable isotope of naturally occurring plutonium has a half-life of only 82,000,000 years and is exhausted well before it can be taken up in planetary formation. However, humans have been able to artificially create plutonium.
The first sample of plutonium humans ever produced was made at the University of California in 1941. Researchers at the university bombarded a sample of uranium-238 with helium nuclei until it formed neptunium-238. This isotope has a short half-life. Within a few days, the sample had decayed into plutonium-238.
After World War II, the United States extracted plutonium from spent uranium fuel rods on an industrial scale. Plutonium-239 is particularly useful for weapons and civilian power production. This work lasted for decades until the 1970s, when President Ford issued an executive order to suspend plutonium production in civilian facilities over fear of nuclear proliferation. Several nations, such as France, Japan and Russia, have substantial investments in large-scale reprocessing and have continued producing plutonium from spent uranium. Plutonium can be used to produce nuclear weapons and to generate nuclear power.