What is Pluto?

Overview

Pluto, once considered the ninth planet, is now classified as a dwarf planet in the Kuiper Belt, far beyond Neptune. It's a small, icy world with a unique orbit.

  • Diameter: 2,377 km
  • Distance from Sun: 5.9 billion km
  • Mass: 1.31 x 10²² kg
  • Orbit Period: 248 years
  • Rotation Period: 6.39 days
Pluto from New Horizons

Image credit: NASA/JHUAPL/SwRI

Details

Atmosphere: Thin and temporary, mostly nitrogen with methane and carbon monoxide, forming when Pluto nears the Sun.

Moons: Five known moons, with Charon being the largest—almost half Pluto's size, forming a binary system.

Surface: Covered in ice with a heart-shaped region (Tombaugh Regio) and rugged mountains.

Exploration: Visited by NASA's New Horizons in 2015, revealing a surprisingly complex world.

Fun Fact: Pluto's orbit is so elliptical it sometimes crosses inside Neptune's path.