Some 94 years ago on February 18, 1930, American astronomer Clyde Tombaugh discovered Pluto and named it as the ninth planet in our solar system. Soon after, Caltech professor of astronomy, Mike Brown, revoked Pluto’s planetary status. Pluto has since then remained a topic of debate among the science community.
In 2006, members of the International Astronomical Union changed the criteria of what can be described as ‘planets’, leading to the demotion of Pluto to a dwarf planet. The IAU decided in 2006 that a planet must be spherical, orbit the sun and have gravitationally “cleared” its orbit of other objects.
While Pluto checks the first two categories, it shares its orbit with objects called “plutinos” it didn’t qualify under the new definition.
Scientists and astronomers have been debating over this IAU decision for years and the question remains. Should Pluto be renamed as a planet?
How was Pluto discovered?
American astronomer Percival Lowell first suggested that Pluto existed in 1905 when he observed strange deviations in the orbits of Neptune and Uranus. Lowell suggested there must be some other celestial body whose gravity is tugging on these ice giants, causing discrepancies in their orbits. Lowell proceeded to predict the mystery planet's location in 1915. Clyde Tombaugh at the Lowell Observatory discovered Pluto in 1930 based on predictions by Lowell and other astronomers.
Why is Pluto no longer considered as a planet?
Pluto was considered unique in the 1900s because of its size and influence on Neptune’s orbit. Pluto was small, perhaps only the size of Earth or even Mars. It seemed unlikely it could have much influence over Uranus and Neptune. Observing the planet was extremely difficult at that time, and its small size, combined with its unusual orbit, began to cast serious doubt as to whether Pluto could be a planet at all. With the discovery of CCD cameras, scientists gradually discovered the Kuiper belt and many other Pluto-like objects in the Kuiper belt, leading to the reclassification of the term ‘planets’ by the IAU. Pluto was then classified as a ‘dwarf planet’.
What is the debate?
Many astronomy voices debate that Pluto was initially named as a planet for most of its historical existence and the decision creates a lot of confusion in this matter. According to some scientists, IAU’s decision regarding Pluto’s demotion is inconsistent as Earth orbits with 10,000 near-Earth asteroids, while 100,000 Trojan asteroids lie within Jupiter’s orbit. But Earth and Jupiter are considered planets regardless of their failing IAU’s criteria.
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