Pluto is so far from Earth that what humans know about it can be counted on one hand.
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However, in the coming years, things will become clearer when NASA’s New Horizons spacecraft is expected to reach this celestial body in July 2015. So far, there are 5 extremely mysterious facts about Pluto, which was once considered the ninth planet of the solar system before being reclassified as a dwarf planet by the International Astronomical Union in 2006.
Misconceptions About Size
When discovered in 1930, Pluto was initially thought to be larger than Mercury and possibly even larger than Earth. Now, astronomers know that it is only about 2,352 kilometers in diameter, 20% smaller than Earth, with a mass that is only 0.2% of our planet.
Chaotic Orbit
Pluto has an unusually flat elliptical orbit, unlike the 8 planets in the solar system. On average, this dwarf planet takes about 248 years to complete its orbit of 5.87 billion kilometers around the Sun. This unusual orbit means that for several years, Pluto’s orbit crosses that of Neptune. This brings Pluto closer to Earth compared to Neptune, the eighth planet from the Sun. But there’s no need to worry; these two planets will never collide, even though their orbits overlap.
Oddly Low Temperatures
Because it is so far from the Sun, Pluto is one of the coldest places in the solar system, with surface temperatures consistently around -225 degrees Celsius. Its surface is regularly covered with nitrogen ice. When viewed up close, the surface of this dwarf planet can appear as icy mountains filled with cold gases, and there may be a massive ocean beneath the surface.
Moons
Pluto has 4 moons: Charon, Nix, Hydra, and a tiny recently discovered moon named P4. While Nix, Hydra, and P4 are relatively small, Charon is about half the size of Pluto. Due to Charon’s impressive size, some astronomers believe that Pluto and Charon are a pair of dwarf planets, also known as a binary system. This term refers to two celestial bodies locked together by gravitational forces. Charon always shows one face to Pluto, and Pluto also always shows one face to Charon. It can be imagined that if a person stood on the near side of Pluto, Charon would appear to hang in the sky without moving; if that person walked to the far side, they would not be able to see Charon.
Thin Atmosphere
Despite being smaller than Earth’s moon, this peculiar dwarf planet manages to maintain a thin atmosphere, primarily composed of nitrogen, methane, and carbon monoxide, extending about 3,000 kilometers thick.
