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Is Pluto a planet anymore?

The International Astronomical Union (IAU) has defined a planet as a celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a nearly round shape and has cleared the neighborhood around its orbit. Therefore officially, Pluto qualifies only as a dwarf planet of the solar system.

Pluto was discovered by astronomer Clyde Tombaugh at the Lowell Observatory in Arizona on February 18, 1930. Pluto has a highly eccentric orbit. Its average distance from the Sun is about 5.90638 x 109 km (39.482 A.U.) which is approximately 40 times that of Earth’s distance from the Sun.

Pluto's astronomical symbol is a combination of the two letters, "P-L".

Once considered as the smallest planet in the Solar System, Pluto is also smaller and less massive than seven moons namely Ganymede, Titan, Callisto, Io, Earth's Moon, Europa and Triton.

Pluto completes one full revolution around the Sun in 248 Earth years. Pluto's most recent close approach to the Sun was in 1989. Between 1979 and 1999, Pluto's highly elliptical orbit brought it closer to the Sun than Neptune, providing rare opportunities to study Charon (the only moon ofPluto).

Pluto is believed to have a rocky core surrounded by a mantle of ice. Its surface is covered with a bright layer of frozen methane, nitrogen, and carbon monoxide. During its highly elliptical orbit, when it reaches its closest point to the Sun, these ices melt, rise, and temporarily form a thin atmosphere and when it is traveling away from the Sun the bulk of the planet's atmosphere freezes.

Discovery and Naming of Pluto
Pluto was discovered by the astronomer Clyde Tombaugh at the Lowell Observatory in Arizona on February 18, 1930.

Tombaugh urged the director of Lowell Observatory, Vesto Melvin Slipher, to suggest a name for the new planet before someone else did. People from around the world started sending in their suggestions. Names like Zeus Artemis, Athene, Atlas, Cosmos, Hera, Hercules, Icarus, Idana, Odin, Pax, Persephone, Perseus, Prometheus, Tantalus, Vulcan, Zymal etc received maximum support. The problem facing the astronomers was that a majority of the mythological names had already been allotted to the numerous asteroids, all female names had been taken up by other bodies and male names were only allotted to objects which had unusual orbits.
Pluto & Charon

The name Pluto was suggested by an eleven-year-old girl from Oxford, Venetia Burney. Her grandfather asked what she thought would be good name for the newly discovered planet. Venetia suggested that as the planet had severely cold conditions and was distant it should be named after the Roman God of the underworld,Pluto. The name Pluto was officially adopted on May 1, 1930.

Pluto’s Moon
Pluto has three known moons, Hydra, Nix and Charon. Charon was discovered in 1978 while the two other moons Hydra and Nix were discovered in 2005.

Pluto and Charon are locked into a mutually synchronous orbit which keeps each one facing the other with the same side. This is the only case in which a planet always presents the same hemisphere to its moon.

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