Before 21st century, Pluto was considered as a planet. Unfortunately, after summer of 2006, its status was lowered to the draft planet. This research paper highlights the history of discovery of Pluto and its relation to mythology. It explains why Pluto was eliminated from the planet row of the Solar System.
Over many years, Pluto was considered as the ninth planet of the Solar System. Unfortunately, it was deprived of this right. The International Astronomical Union decided that this celestial body could not be considered as a planet. Under the new definition, in our solar system, there are only 8 planets. Pluto does not meet the requirements of the new formulation and loses its "planetary status". Thus, it is moving into a new quality and becomes of other separate class called “dwarf planets”.
In 1930, the astronomer Clyde Tombaugh has discovered Pluto at observatory of Arizona. He was searching during fifteen years, since the existence of the planet was predicted by Percival Lowell and his theory of the perturbations in the motion of Uranus and Neptune. These calculations were wrong, but by the chance, Pluto was discovered near the predicted location. Pluto is the only planet, which has never been visited by any spacecrafts. Therefore, it is little known about the characteristics of the planet. The largest of Pluto's satellite Charon got its name from the mythological ferryman who ferried the dear to the underworld across the river. In mythology, Charon ferries dead through the underground river in return for a fee. He carries only the dead whose bones found peace in the grave. However, he does not ferried back under any circumstances. In turn, Pluto is a god of the underworld.
Since the end of the 20th century, astronomers constantly find beyond the orbit of Neptune celestial bodies with a diameter of a few hundred to several thousand kilometres. Together, they are sometimes called the Kuiper belt. There are some factors that determine neither the celestial body is a planet or not. Pluto does not meet one of the factors. The mass of the satellites that are not in its orbit is too large compared to the mass of Pluto to assume that it dominates. Moreover, in 2003, on the edge of the Solar System, there was found the object UB 313, exceeding the size of Pluto.
Since its discovery, Pluto was considered as a planet, but due to the fact that his real weight was originally defined incorrectly and was significantly lower than expected, and due to a number of unique features Pluto often appear under question. Now Pluto-Charon system is a double dwarf planet.