We learned that Pluto was the ninth and the last planet out from the sun, and then everything changed this when a 2006 IAU (International Astronomical Union) statement was released. According to IAU, the new definition of a planet is that of a body that orbits the sun without being a moon of another object.
Moreover, it is big enough that its gravity has shaped it into a sphere, and has removed its proximity of most other bodies. Pluto didn’t succeed in keeping its title of a planet, and it was downgraded to dwarf planet. Also, according to IAU measurements, Pluto is situated on the edge of the Kuiper Belt, known for its icy objects beyond Neptune, and has not removed this proximity of most of these things. Pluto, however, might stand a chance to regain its lost title, near in the future.
What We Know About Pluto
Pluto is an incredible discovery based on calculations rather than direct observation. It orbits at almost 5.1 billion kilometers from the sun, and it posses an equatorial diameter of 2,302 km. Also, it has a significant orbital period of nearly 248 Earth years and five moons. Pluto has a deeply unusual orbit, which leads it inside (approximately 20 years) the orbit of Neptune every 230 years.
Pluto’s moons are known as Charon, Nix, Hydra, Kerberos, and Styx (discovered in 2012). As for its four dwarf planets, we mention Ceres (the most prominent object in the central asteroid belt between Mars and Jupiter_, Haumea (has two moons), Eris (considered Pluto’s twin due to its dimension), and Makemake (has one moon). We couldn’t find out so much information about Pluto if it weren’t NASA’s New Horizon mission, which flew by the planet in July 2015.