Why isn't Pluto a planet?

Pluto is no longer a planet because of its size. The scientists noticed this factor, because a dwarf planet named Eris, made out of the same rock/ice mixture as Pluto, is larger than Pluto. In result of the scientist's discovery they classified Pluto as a dwarf planet.

Pluto Facts

* Discovered by: Clyde W. Tombaugh

*Discovered on: February 18,1930

* Mass: 1.30900 x 10(22) kg

* Distance from the sun: 5.9 billion km

* Rotation period (earth days): 6.375 days (153 hrs)

* Revolution period (earth years): 248 years

* Atmosphere (principal gasses): presumably thin, tenuous atmosphere

        * Interesting fact: atmosphere expands when it comes close to the sun and collapses as it moves farther away.

* Composition: unknown probably 70% rock and 30% water/ice { probably nitrogen ,solid methane, ethane, carbon monoxide

* Surface temperature: -229 C

* Know moons: Charon(discover in 1978)

* Hydra and Nix(both discovered in 2005)

* Kerberos(discovered in 2011) originally name P4

* Styx(discovered in 2012) originally name P5

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