Dwarf Planet Pluto


Pluto is a Dwarf Planet. It used to be classed a planet and used to be the farthest known planet from the Sun. It has five moons including called Charon moon.

The Planet Pluto with the Charon Moon

Pluto was discovered in 1930 by Clyde W. Tombaugh. The planet is named Pluto after the God of the Underworld in Roman mythology. In Greek mythology the equivalent god is Hades.

Facts about Planet Pluto

* Diameter: 2324 km (1444 miles).

* Surface composition: Nitrogen, carbon monoxide, methane and water ices

* Average surface temperature: -233ºC (-382ºF)

* Mass: 0.002 (Earth = 1)

* Gravity: 0.07 (Earth = 1)

* Average distance from the Sun: 5.9 billion kilometres.

* Rotation Period: 6.39 Earth days (length of day)

* Orbital period around the sun: 248 Earth years (length of year)

* Rings = 0

* Moons =  5

* Average distance between Pluto and Charon: 19,600 Kms

The Orbit of Planet Pluto

Pluto’s orbit from the Sun varies from 4.4 to 7.7 billion kms and for the most of its orbit it is the outer most planet. Between 1979 and 1999 Pluto was actually closer to the Sun than Neptune and the closest approach to the sun (perihelion) was in September 1989.

Due to the changes in orbit in time, Pluto has a unique atmosphere that transforms at various stages of its orbit. As its orbit approaches the Sun, its atmosphere begins to form. The frozen atmosphere melts as it comes closer. As Pluto moves further out its atmosphere will freeze.

Is Pluto a Planet

In August 2006, Pluto was demoted from a planet to a dwarf planet by the International Astronomical Union (IAU). It official name became ‘134340 Pluto’.


Features a large heart-shaped region known unofficially as Tombaugh Reggio which is about 1000 miles (1600km) wide.


Pluto is smaller than Planet Mercury and seven other moons including Callisto, Earth’s Moon, Europa, Ganymede, Io, Titan, and Triton.


It’s thin and almost entirely nitrogen.



Pluto rotates backward compared to Earth and most other planets. Pluto goes from east to west like Venus and Neptune. It also rotates on its side like Neptune.

A single day on Pluto is equal to 6.4 Earth days.


There are five Moons of Pluto:  Charon, Hydra, Kerberos, Nix and Styx. Charon is the largest moon and has a diameter just over half that of Pluto.

Charon Moon

Charon was discovered in 1978. Its diameter is 1212 km (753 miles) which is more than half as wide in size as Pluto and the Pluto-Charon system is like a double planet. Charon orbits Pluto every 6.4 days and has a synchronous orbit (the pair show the same face to each other all the time). To an observer on the planet, Charon appears to be stationary in the sky like a geostationary satellite orbiting the Earth.

Binary System

Pluto and its moon Charon are actually a binary system. They are both orbiting around around a centre which is located between the two bodies.


NASA has for at least a decade been planning a fly-by of the solar systems most distant planet. The latest version, called New Horizons will be launched in 2006.

In the mid 1990’s NASA began a development of the Pluto-Kuiper Express spacecraft. In mid-September, 2000, however, NASA issued a stop-work order on the project. NASA then began to talk of a plan which would have a probe arrive before 2020 and that would cost less than $500 million (2002 dollars).

As a result Nasa started a competition and it chose a team called New Horizons to build a spacecraft that will study Pluto, Charon and several Kuiper Belt objects during a series of flybys. It will be launched in 2006 and will arrive in 2015.

What was Pluto-Kuiper Express?

NASA was developing a robotic reconnaissance mission to Pluto called Pluto-Kuiper Express. The Pluto mission would have used lightweight advanced-technology hardware components and advanced software technology. The Pluto mission plan called for launch when this technology was ready. It was scheduled for launch in 2004 and to arrive at Pluto in 2012.

In 2000 a website was started to save the Pluto-Kuiper Program (External Link).


New Horizons: Reconnaissance of the Pluto-Charon System and the Kuiper Belt by C.T. Russell
From Amazon.comAmazon.co.ukAmazon.ca

Pluto and Charon : Ice Worlds on the Ragged Edge of the Solar System by Alan Stern, Jacqueline Mitton
From Amazon.comAmazon.co.uk

Pluto: The Ninth Planet by Michael D. Cole
From Amazon.comAmazon.co.uk

Beyond Pluto by John Davies (Author)
From Amazon.comAmazon.co.uk

The Planet Pluto Links:

Any comments or suggestions on Planet Pluto, then click on Contact Info.