Pluto and moon Charon from HST

credits: image of Pluto and Charon taken by Hubble Space Telescope

Pluto was discovered in 1930 and named after the Roman god of the dark underworld. It may have received this name because itís always in darkness since it is so far from the Sun

Pluto was once known as the ninth planet and the furthest from the Sun. It was also the smallest planet. On August 24, 2006 Pluto's status as a planet was changed to a "dwarf planet".

We do not know much about Pluto because it is so far from Earth. It looks like a fuzzy blob even with the most powerful telescopes. It is over 5.9 billion km (three and a half billion miles) from the Sun. The light from the Sun looks very dim from Pluto. (note the sun in the image below)

"Artistís impression of how the surface of Pluto might look.
The image shows patches of pure methane on the surface."
credit: ESO (European Organisation for Astronomical Research in the Southern Hemisphere)

Pluto is smaller than Earth's moon and has a moon named Charon which is about half the size of Pluto. Two additional small moons (Nix and Hydra) were spotted by the Hubble Space Telescope in 2005.

Pluto and moons (Charon, Nix and Hydra) taken Feb.16,2006
Pluto and moons, HSTimage, 2006
Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI),
and the HST Pluto Companion Search Team

Pluto is so cold that air can freeze and fall to the ground like snow. Its surface is frozen nitrogen, methane, and carbon dioxide. The interior is probably a rocky core surrounded by ice. There are dark and bright regions across its surface.

pluto's interior, credit : NASA

Pluto rotates once every 6.4 days and spins the opposite direction of most other planets. Like Uranus, Pluto rotates on its side. It takes 248 Earth years to orbit the Sun. From 1979 to 1999 Pluto and Neptune crossed orbits and Pluto was closer to the Sun than Neptune.

The New Horizons Pluto-Kuiper Belt mission was launched in January 2006 and should reach Pluto in July 2015. It takes nine and a half years for the spacecraft to reach Pluto. An airliner would take more than 800 years to get to Pluto!

artist's concept of New Horizons spacecraft
approaching Pluto and its moons in 2015.

Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

"Artistís concept of the surface of Pluto. In the sky are Plutoís largest moon Charon,
and recently discovered moons Nix and Hydra."

Credit: NASA, ESA, and G. Bacon (STScI)


web page by J.Giannetta<>
updated April 2009

New Horizons mission at Space Today