Pluto
Dwarf Planet
Pluto was the ninth planet from 1930 until 2006, when the discovery of the similarly sized Eris led the IAU to formally define 'planet' and reclassify Pluto as a dwarf planet. It has a large, heart-shaped nitrogen-ice plain called Sputnik Planitia and five known moons.
Field Notes
- Pluto's largest moon, Charon, is over half its size — the two are sometimes called a double dwarf-planet system.
- Its heart-shaped Sputnik Planitia is a vast plain of nitrogen, methane, and carbon monoxide ice.
- Pluto's orbit is so elliptical and tilted that it occasionally passes closer to the Sun than Neptune, as it did from 1979 to 1999.
| Planet Specifications | |
|---|---|
| Radius | 1,188 km |
| Mass | 1.303 × 10²² kg |
| Distance from Sun | 5.906B km |
| Rotation Speed | 47.2 km/h |