Pluto
The most famous dwarf planet — New Horizons revealed mountains of water ice and a heart-shaped nitrogen plain.
- Type
- Dwarf planet (Kuiper Belt)
- Diameter
- ≈2,377 km
- Rotation
- 6.4 days (retrograde)
- Orbit
- 39.5 AU from the Sun
- Discovered
- 1930 · Clyde Tombaugh
- Visited by
- New Horizons (2015)
Its heart-shaped Sputnik Planitia is a vast plain of churning nitrogen ice.
Pluto was imaged in a single flyby in 2015. With its slow 6.4-day spin, only the hemisphere facing New Horizons at closest approach — the heart, Sputnik Planitia — was mapped sharply. The far side, seen only from a distance, looks soft and blurry, and the south pole was in winter darkness and went unimaged (the black band). This is the real limit of our data, not a glitch.
