Why is Pluto is Not a Planet: We have always known Pluto as the youngest sibling in the Solar System. But, in 2006 the International Astronomical Union (IAU) demoted Pluto from its position as the ninth planet from the Sun to one of five “dwarf planets.” The dwarf planet is about 3.6 billion miles away from the sun. Once little Pluto was a part of our solar system and all those planetarium engravings, printed in first grade science books. In less than 80 years after its official designation as a planet, the title was stripped away.
Brief Overview About Pluto
|Mass||1.31 x 10^22 kg (0.17 Moons)|
|Orbit Distance||5,874,000,000 km (39.26 AU)|
|Orbit Period||248 Years|
|No of Moons||5 (Charon, Styx, Nix, Kerberos, and Hydra)|
NASA Solar System Exploration – Discovery of Pluto
Pluto was discovered by an American astronomer, Clyde Tombaugh in the year 1930 as ‘Planet X’. The name Pluto comes from the name of the Greek god of the underworld, suggested by an eleven-year-old schoolgirl in England. The total diameter & Mass of Pluto are 2,372 km & 1.31 x 10^22 kg. The initial calculations showed its mass to be equivalent to that of Earth’s and in 1948, it was estimated to be close to Mars’ mass. Pluto has 5 moons namely Charon, Styx, Nix, Kerberos, and Hydra. In 1978, Charon, Pluto’s largest moon unleashed its actual mass which turned out to be barely 0.2% of the Earth’s mass and Pluto was found to be tiny.
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Why is Pluto is Not a Planet?
The year 992 marked the discovery of the Kuiper Belt, a collection of celestial bodies extending 55 astronomical units from the orbit of Neptune. Not only Pluto was found to be a part of this belt, but it was estimated that there exist another 70,000 icy bodies with the same composition as that of Pluto. In 2005, Eris, a trans- Neptunium object, was discovered, which was substantially more massive than Pluto, a little bigger in size and its orbit was found be of the same size, probably even larger, than Pluto’s orbit. Amidst the controversy, the General Assembly of the International Astronomical Union (IAU) was held on 24th August, 2006, which established the ground rules for a celestial body to qualify as a planet. According to new rules –
- A planet must be round.
- A planet must orbit the sun.
- A planet must have “cleared the neighborhood” of its orbit.
Pluto follows the first two rules – It is round, and it orbits the sun. But, it does not, however, follow the third rule. It has not yet cleared the neighborhood of its orbit in space. Because it does not follow this rule, Pluto is no longer considered a planet. I hope you got the answer Why is Pluto is Not a Planet?