Pluto was named after the Roman
mytholoqical god of the underworld, because the planet is dark and cold.
Pluto is usually the ninth planet from the Sun, but once every 248 years for a
period of 20 years, Pluto switches places with Neptune, which means Pluto
would then be the eighth planet from the Sun. Pluto is also the smallest
planet in the Solar System; it is so small that when viewed through a telescope, it
looks like a star, asteroid, or comet. The planet is so small that the
Hubble Space Telescope finds it hard to take clear pictures of it.
In fact, Pluto is smaller than the Earth's Moon, and is 2/3 the diameter of Earth. The surface materials
of Pluto are methane ice and rock; it has an atmosphere of methane and
nitrogen. Pluto's atmosphere appears to extend out to include its moon,
Charon, which suggests that they may share an atmosphere. Pluto, called the
ice planet, is the farthest planet from the Sun, therefore the coldest. The
temperature drops to -233 degrees Celsius. During the time when Pluto is
farthest from the Sun in its orbit, its atmosphere condenses and falls to its
surface as frost.
The distance from Pluto to the Sun is about 5.9 billion km. It's hard for scientists to determine how far from the Sun Pluto actually is because Pluto has an unusual orbit, it is very elliptical or egg-shaped, not round, therefore the distance from the Sun continuously changes. It takes 248 Earth years to orbit the Sun; one of Pluto's days is over 6 Earth days.
There are many things yet to be discovered about Pluto, such as whether there's life on Pluto or not. NASA scientists have proposed a space mission to Pluto called the "Pluto Kuiper Express", using a high speed spacecraft. Pluto has never been explored by a spacecraft, so this would give humans the first close-up look at Pluto which has only one satellite or moon; Pluto and its large moon Charon may be a double planet system. Astronomers hope to be there by the year 2010 or later. This would give them the chance to solve many questions yet to be answered.
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