Helium, the second element in the periodic table, is the second-most abundant element in the universe after hydrogen. It is a noble gas that is unreactive (because of its filled outer electronic shell), colorless, and odorless. Helium is found in great abundance in many stars, such as the Sun, and is an important component in both the proton-proton reaction and the carbon cycle, which account for the energy of the Sun and stars. The energy released as hydrogen is fused into helium and is the source of the power contained in a hydrogen bomb. Under 25 atmospheres of pressure, helium has a boiling point of -268.9°C (-52.1°F or 4.22K) and a melting point of -272.2°C (-458°F or 0.95K). At this temperature, slightly above absolute zero, helium is transformed into helium II, superfluid helium, a liquid with unique properties.

French astronomer Pierre...