Pluto

           Pluto is the last planet in our Solar System. Pluto follows the most elliptical orbit than any other planet. Part of its orbit lies inside Neptune's orbit and until 2000 A.D. it will stay nearer to the Sun than Neptune. Pluto lies at a mean distance of 5,900 million km. from the Sun. Pluto. The rotation period of Pluto is about 6 days and revolves round the Sun in about 247.7 Earth years. From Pluto, the Sun appears as a tiny point of light, but a point which is about 440 times brighter than the full moon from the Earth.
           According to one theory Pluto is an escaped satellite of Neptune which somehow broke free and moved along in an independent orbit. The planet seems to be a snowball of frozen gases, with a surface temperature of about -220^o C. Some scientists thinkthey may have detected a tiny atmosphere.
           The search for still more planets continued into the present century. In 1930 an American astronomer named Clyde Tombaugh was succesful. He spotted a tiny moving 'star', which proved to be a ninth planet. In 1978, James W. Christy, of the U.S. Naval Observatory, observed, rather we can say, discovered that Pluto has a moon. He calles it Charon (after the mythical boatman who ferried boats across the river stays into the Greek underworld.
           We know little about Pluto. It is so distant that it appears only as a speck in telescopes. Pluto is a very tiny world, and by far is the smallest planet. It is much smaller even than our Moon. It also has a moon of its own, called Charon. The diameter of Pluto is about 5,800 km. and the diameter of Charon is about 1,200 km. Charon is believed to orbit about 20,000 km. above Pluto's crust. The closeness and similarity in size of Pluto and Charon, makes some astronomers consider them as a double planet rather than a planet and satellite.

PLUTO Diameter at equator: 2,284 km Mass (Earth = 1): 0.002 Volume (Earth = 1): 0.005 Density (Water = 1): 2 Distance from Sun: 5,90,00,00,000 km Orbits the Sun in: 247 years 8 months Spins on axis in: 6 days 9 hours Temperature average: -230oC Moons 1

The Planet Hunters            After the discovery of Uranus in 1781 and Neptune in 1846, astronomers found that their orbits were not quite right. This made them think there must be a ninth planet.            In the early 1900s, the American astronomer Percival Lowell, worked out where he thought the new planet should be: somewhere in the constellations Gemini or Taurus. He started looking for it, but in vain.            A young astronomer named Clyde Tombaugh eventually continued Lowell's work at his observatory in Flagstaff Arizona. He began searching for the new planet in 1927.            On Feb 29, 1930, he was looking at two pictures taken on Jan 13 and 27. One 'star' had moved. It was no star, but a new planet - Pluto. It was close to where Lowell Had said it would be.

Planet X            Some astronomers do not think Pluto is the last planet. It cannot cause the wobbles in the orbits of Uranus and Neptune because its gravity is too low.            They reckon that there must be a tenth planet, Planet X. It must lie a very long way away, otherwise it would have been discovered already. And it must be large - to cause the disturbances in the orbits.