Hobbies And Interests
Discovery
In the late 19th century, astronomers first began speculating that a ninth planet was altering Uranus's orbit. Percival Lowell, founder of Lowell Observatory in Flagstaff, Arizona, began funding the search for this new planet in 1906, which he dubbed Planet X. Lowell's search for the ninth planet ended with his death in 1916, though his observatory unknowingly captured two images of Pluto without recognizing their significance. Clyde Tombaugh resumed the search in 1929, and finally pinpointed Pluto the following year.
Pluto's Eccentric Orbit
Unlike the planets of the solar system, Pluto's orbit is extremely "eccentric," or elliptical. This means that for about 20 of the 248 Earth years that it takes to orbit the sun, Pluto is actually closer to the sun than Neptune. The last period that Pluto was closer to the sun than Neptune was from February 7, 1979, until February 11, 1999. Despite their overlapping paths, Pluto and Neptune never come remotely close to each other.
Kuiper Belt
Pluto's status as a planet came into question with the discovery of the Kuiper Belt in 1992. The Kuiper Belt is a massive region just outside of the planets that is filled with smaller bodies. The elements that compose Pluto are nearly identical to those that make up the other objects in the Kuiper Belt, and the subsequent discovery of larger Kuiper Belt Objects with similar orbital periods cause some scientists to reconsider Pluto.
Dwarf Planet
When scientists discovered Eris, an object outside of the Kuiper Belt that is 27 percent larger than Pluto, the International Astronomical Union was compelled to establish a formal definition of what a planet is. Part of the new definition held that a planet must have "cleared the neighbourhood around its orbit," meaning that it must not share its orbit with other objects. Pluto does not fit this category and was therefore reclassified as a dwarf planet.
Charon, Nix and Hydra
Charon is a satellite of Pluto, classified as Pluto's moon upon its discovery in June 22, 1978. The fact that it is more than half the size of Pluto has led some to argue that Pluto should be categorized as a binary planet system. Pluto's reclassification as a dwarf planet did not result in an official reclassification of Charon; it remains classified as a moon. Nix and Hydra, two smaller satellites, were discovered in 2005.