Pluto is the farthest known planet from the Sun. It the only one planet that has
not been visited by spacecraft. It has five moons including called Charon
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:
* Mass: 0.002 (Earth = 1)
* Gravity: 0.07 (Earth =
* Average distance from the Sun: 5.9
* 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:
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.
There are five
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.
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
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
As a result Nasa started a competition and it chose a team called
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
New Horizons: Reconnaissance of the Pluto-Charon System and the Kuiper Belt
by C.T. Russell
Pluto and Charon : Ice Worlds on the Ragged Edge of the Solar
System by Alan Stern, Jacqueline Mitton
Pluto: The Ninth Planet by Michael D.
Beyond Pluto by John Davies (Author)
The Planet Pluto Links:
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