Pluto is the most distant and smallest planet in the solar system. It takes 6 days 9 hours to rotate and 248 Earth years to orbit the Sun.

The littlest planet of allThe littlest planet of all

Not only is Pluto the smallest planet but it is smaller than seven of the solar system’s moons.

Pluto’s only moon, Charon, is roughly half the size of the planet. Some astronomers consider Pluto and Charon to be twin planets, instead of planet and moon.

Double PlanetDouble Planet

Unusual orbitUnusual orbit

Pluto's orbit is highly eccentric. At times it is closer to the Sun than Neptune (as it was from January 1979 thru February 11 1999). Pluto is locked in a 3:2 resonance with Neptune; Its orbital inclination is also much higher than the other planets'. Thus though it appears that Pluto's orbit crosses Neptune's, it really doesn't and they will never collide.

Frozen PlanetFrozen Planet

Pluto's exact composition is unknown, but its density (about 2 gm/cm3) indicates that it is probably a mixture of 70% rock and 30% water ice much like Triton and other comets.

This is a true color image of Pluto. It’s brown color is thought to be frozen methane deposits.

These pictures by the Hubble Space Telescope show the surface detail on the two opposite hemispheres of Pluto.

Pluto has a thin atmosphere that appears when it is close to the sun. Its temperature ranges from -378 to -396 degrees F (-228 to -238 C).

Hubble ViewHubble View

Image: NASA

Kuiper Belt ObjectsKuiper Belt Objects

• Some believe Pluto to be a very large “ice dwarf” or Kuiper Belt Object.

• These objects are the size of asteroids or small planets, but are mostly ice, like a comet.

• They are very numerous and reside past the orbit of Neptune in the far outer solar system.

Image: NASA

- Pluto Diameter: 2390 km, 0.2- Earth Diameters Planetary Mass: 1.25x1022 kg, 0.0025 Earth masses- Average Distance from Sun: 5.913 billion km, 39.53 AU (astronomical units)- Length of Day: about 6.4 Earth Days- Length of Year: 248.53 Earth Years- Day/Night Surface Temperature: 54-59 degrees Kelvin- Number of natural satellites: 1 – Charon- Planetary ring system: None- Average temperature: ~50 K (-223 C)- Atmospheric composition: Methane (CH4), Nitrogen (N2)

More informationMore information

Earth ComparisonEarth Comparison

Distance from Sun 36.7 Billion Miles 93 Million Miles

Diameter 1430 Miles 7926 Miles

Length of Year 248 Earth Years 365.25 Days

Length of Day 6 days 9 hours 23 hours 56 minutes

Gravity .07 that of Earth 2.66 times that of Mars

Temperature Range -228 C to -238 C -88 C to 58 C

Number of Moons 1 1

EARTHPLUTO

Pluto being a cold, dark planet was named after the Roman god of the underworld where souls went after death.

It is also intended to evoke the initials of the astronomer Percival Lowell who predicted that a planet would be found beyond Neptune

God of the UnderworldGod of the Underworld

Pluto was discovered by the astronomer Clyde Tombaugh at the Lowell Observatory in Arizona on February 18, 1930. It’s moon, Charon, was discovered in 1978 by Jim Christy.

You are HereYou are Here

Image: NASA

NASA’s New Horizons is the first mission to the last planet - the initial reconnaissance of Pluto-Charon and the Kuiper Belt - sent out to explore the mysterious worlds at the edge of our solar system. New Horizons is scheduled to launch in January 2006.

New Horizons- NASANew Horizons- NASA

Image: NASA