Pluto, which was previously a planet, has recently been classified under the members of the Kuiper belt. Pluto is now the largest member of the Kuiper belt region.
Although Pluto orbits the Sun and it's round, it's not a planet. And that's because Pluto hasn't cleared out its orbit of material. This was the reason that the International Astronomical Union chose to demote it from planet to dwarf planet in 2006.
The name "Pluto" was proposed by Venetia Burney, an eleven-year-old schoolgirl. Venetia was interested in classical mythology as well as astronomy, and considered the name, one of the alternate names of Hades, the Greek god of the Underworld, appropriate for such a presumably dark and cold world.
Pluto is so far from the Sun, it takes sunlight over 5 hours to reach it. In contrast, sunlight reaches the Earth in 8 minutes.
Pluto orbits the sun once ever 248 years.
Measurements indicate Pluto is the smallest planet, 2320 kilometers (1440 miles) in diameter. It is smaller than Earth's Moon.
Pluto is cold: -233� C (-390 F), just 40 C (72 F) above absolute zero. At this temperature, all elements would be frozen but neon, hydrogen, and helium. On Earth, we breathe these gases to live.
Pluto is believed to have an average temperature of roughly -63 degrees Celsius.
Pluto has three natural satellites of its own. Charon was discovered in 1978 while the other two satellites namely, Nix and Hydra were found in 2005. Pluto's moons are exceptionally close to it. Scientists say that the Plutonian system composed of Pluto and its satellites is very compact.
The first time we will visit Pluto for a significant orbital period is in 2015, when the probe New Horizons is scheduled to arrive. It was launched in January 2006.
Pluto is believed to have two additional moons, but their existence has yet to be confirmed.
Pluto has an eccentric orbit, which means it is occasionally closer to the Sun than Neptune.
Pluto is believed to be roughly 70 percent rock and 30 percent water.
Nothing definitive is known about the atmosphere of Pluto or whether it even has one.
One theory suggests Pluto is not a planet, but a twin moon to Triton. Triton is the moon orbiting Neptune and seems to have nearly the same characteristics of Pluto.
One day on Pluto is equivalent to 6 and a half days on Earth.
Not much is known about the surface of Pluto. The Hubble telescope has gotten some pictures of the surface but it could only pick up the largest of the surface features. Larger and more powerful telescopes are being built everyday. Perhaps some day soon the surface will be seen in greater detail.