Discovered in 1898 by Sir William Ramsay and Morris Travers, krypton (Kr) and xenon (Xe) are two of the rarest elements on Earth. They were formed with all the other elements billions of years ago by earlier generations of stars. Astronomers assume that they were synthesized during the supernovae of very heavy stars and in stars of mid-range mass like our Sun.
Until recently, there was no spectroscopic proof of krypton or xenon from the Sun or other stars – although astronomers detected krypton in interstellar space. It was assumed it occurred with the same frequency in the Sun and other stars. Finding a star with measurably higher krypton (and xenon) frequency would demonstrate that both elements were formed there. That is exactly what the team has done – finding these elements in a white dwarf. The astronomers using NASA’s Far Ultraviolet Spectroscopic Explorer, or FUSE, have observed the burnt-out star RE 0503-289.