The Little Planet That Could
Although it has been “demoted” in 2006 and is no longer classified as a planet, that doesn’t make Pluto any less interesting or fascinating. But what are the reasons for that decision, that sparked such controversy? Discovered on February 18th, 1930 by Clyde Tombaugh of the Lowell Observatory, Pluto was classified as a ninth planet from the Sun.
However, its status was brought into question as a result of further research of the Solar System. With the discovery of a minor planet, designated as 2060 Chiron, in 1977, numerous objects similar to Pluto were found. It was this discovery that prompted the International Astronomical Union to reconsider Pluto’s status as a planet. This was done by introducing a new definition of a planet, which excluded Pluto, and also by introducing a new category called a dwarf planet, and Pluto has been classified as such ever since. Some scientists stand by their decision that Pluto should have remained a planet, and that other dwarf planets should be added to the roster of planets in addition to Pluto.
Named after a Greek god (and not a dog, although Mickey Mouse would beg to differ) of the underworld, who is better known by its other name, Hades, Pluto is a planet which we know very little about. We know that its diameter is less than one fifth of the Earth’s diameter, and that it probably consists of a solid, rocky core, surrounded by ice, namely frozen methane and nitrogen. Pluto’s orbit is eccentric, which means it is far from a perfect circle, and its distance from the Sun varies drastically depending on the location. Its atmosphere also depends on whether is or not Pluto is close to the Sun. With the temperature on the surface of the planet being only 44 degrees above absolute zero, the ice thawes as Pluto’s orbit brings it closer to the Sun, and forms a thin atmosphere consisting mostly of nitrogen and methane, which extends much higher than that of Earth’s, because of Pluto’s low gravity, which is about 20 times less powerful compared to Earth’s gravity. Even though it has such an inconsistent atmosphere, it can still experience strong winds.
Pluto has five known moons: the largest one, dubbed Charon, after a mythological ferryman that carries the souls of the dead across the river Styx, which is also the name of one of its moons, with others named after creatures from Greek mythology as well, Nix, Hydra, and Kerberos. In the last few years, astronomers have discovered several objects which have ice geysers, such as Saturn’s moon Enceladus, and many others as well. In light of this new evidence, it is suspected that Charon could have geysers too, which are spreading ammonia hydrates and water crystals across the surface.
Pluto’s distance has made it very hard for scientistst to see it with telescopes, in addition to never being visited by a spacecraft. However, NASA’s New Horizons mission launched a probe in January 2006, which is expected to study Pluto and its moons. It will attempt a close approach in July 2015, carrying some of the ashes of Pluto’s discoverer, Clyde Tombaugh.