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Pluto is named after the Roman god of the underworld, the equivalent of Hades in Greek mythology. It was considered a planet from its discovery in 1930 until 2006 when it was demoted to the category of dwarf planet.
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Uranus and Neptune were discovered in 1781 and 1864, respectively. The discovery of Pluto came after Percival Lowell in 1906 realized that something influenced the orbit of these last two planets to be found. From then on, Lowell began his search for Planet X. In 1916, the astronomer passed away, but not before leaving a legacy and a lot of money for this new planet to be discovered. The search continued until 1930, when Clyde Tombaugh found Pluto among the stars.
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The criteria for a celestial body to be considered a planet are:
- Being in orbit around a star;
- Be large enough for gravity to make it spherical;
- Being gravitationally dominant of its own orbital zone.
Although Pluto meets the first two requirements, it is not dominant in its orbit, as it intersects with that of its icy neighbor Neptune, which is the dominant one.
- Data about Pluto.
- Diameter: 2,376.6 km;
- Average distance from the Sun: 5.9 billion km;
- Gravity: 0.62 m/s²;
- Orbit period: 248 Earth years;
- Rotation period: 6.38 Earth days.