Pluto: The Forgotten Planet

Pluto is a dwarf planet in Kuiper belt. Clyde Tombaugh discovered Pluto in 1930 and declared it to be the ninth planet from the sun. But it was considered as a dwarf planet in 2006. It is the largest planet in the Kuiper belt. Pluto got its name from an 11 year old girl, Venetia Burney of Oxford, England. Its orbital path does not lie in the same plane as the 8 planets, as it is inclined at an angle of 17 degrees. Pluto takes 248 earth years to orbit around the sun. Pluto is smaller than earth's moon as it is 66% of moon's diameter and the weight of it is 18%. Pluto has a distance of 39.5 Astronomical Units (AU), from the sun. Pluto is not the same distance from the sun all the time because of its elliptical orbit. And its closest point from the sun is 29.7 AU. The full name of pluto is 134340 Pluto.

The first satellite to visit Pluto is NASA's New Horizons spacecraft. It visited Pluto on 14 July 2015. Pluto has 5 moons that are Charon, Nix, Hydra, Styx and Kerberos. The atmosphere of Pluto mainly consists of nitrogen, with minor amounts of methane and carbon monoxide. The temperature on Pluto is as cold as -375 to -400 degrees fahrenheit (-226 to -240 degrees celsius). The layers of pluto are outer crust made of frozen nitrogen, frozen layer made of water, and Salicate core made of rocks.

Pluto is not classified as a planet because it does not meet all the three criterias of IAU for a full sized planets. The three criteria of the IAU for a full-sized planet are:

  1. It is in orbit around the Sun.
  2. It has sufficient mass to assume hydrostatic equilibrium (a nearly round shape).
  3. It has "cleared the neighborhood" around its orbit

It does not meet the criteria that is it has "cleared the neighbourhood" around its orbit. So, Pluto is not considered as a planet.

Between 1979 and 1999 Pluto was closer to the Sun than Neptune. During these two decades, Neptune was the ninth planet from the Sun. As it takes 8 minutes for the sunbeams to reach the earth, it takes about 5 hours for the same sunbeams to reach Pluto. Pluto takes about 153 hours to rotate on its axis. Its axis is tilted 57 degrees and spins from east to west like Venus. Pluto's moon Charon is half of the size of Pluto. The other dwarf planets in the Kuiper belt are Eris and Makemake. So, there are 3 planets in the Kuiper belt.

By: Utkarsh Garg 
Class- 5
Sri Venkateshwar International School, 

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