Glossary of Scientific Terms


Previous Term


Glossary Main Index

Next Term




A computer enhanced image of Pluto made from Hubble Space Telescope images taken in 1994.

Typically orbiting the sun beyond the orbit of Nuptune, Pluto is a dwarf planet and takes 248 years to orbit the sun once. Pluto is about 5.5 times smaller than the Earth and is about 450 times less massive. Pluto was discovered on February 18, 1930 by Clyde Tombaugh. Although it was once classified as a planet, Pluto lost this distinction on August 24, 2006.

In Greek mythology, Pluto is another name for Hades, the king of the underworld. Pluto was the son of Cronus and Rhea.

Planetary Data

Distance from SunLength of DayLength of YearRadiusMass
39.48 AU153.3 days247.92 years1,153 km1.3*1022 kg

Known Satellites

NameDistance from PlutoRotational PeriodOrbital PeriodRadius
Charon17,536 km-unknown-6.38725 days603 km
Styx42,000 km-unknown-20.2 days5-12 km
Nix48,708 km-unknown-24.856 days23-68 km
Kerberos59,000 km-unknown-32.1 days6-17 km
Hydra64,749 km-unknown-38.206 days30-84 km

Planetary and Satellite Data: NASA's Solar System Explorer