Pluto is a dwarf planet in the Kuiper belt. Pluto is the first discovered Kuiper Belt object. Pluto is the largest dwarf planet known in the solar system. Pluto ranks 10th in the mass of objects that directly surround the sun. Pluto is the largest overseas celestial body, its quality is second only to Eris in the discrete disk. Like other Kuiper Belt objects, Pluto consists mainly of rock and ice. Pluto is relatively small, only one-sixth of the moon's mass and one-third of the moon's volume. Pluto periodically enters the inner side of the Neptune orbit. Neptune and Pluto will not collide due to mutual orbital resonance.
In 1930 Clyde Tombo discovered Pluto and treated it as the ninth planet. Over the next 75 years, the study of Pluto and other objects in the solar system has challenged Pluto's planetary status. Since the discovery of the asteroid Chajon in 1977, many highly orbiting ice bodies have been found. In 2005, the discrete disk orb revealed the quality of Eris even more than 27% more than that of Pluto. The International Astronomical Union (IAU) formally defined the concept of the planet in 2006, recognizing that Pluto is only one of the larger ice bodies in the outer solar system. The new definition will exclude Pluto from the planet's range and classify it as a dwarf planet. Some astronomers think Pluto is still a planet.
Pluto revolves around the sun a cycle takes about 248 years, its elliptical orbit in the solar system is called the Kuiper belt area. Pluto's elliptical orbit means that it is about 4.4 billion kilometers from the sun when it is in a close position, and about 7.3 billion kilometers from the sun in its farthest position. The surface temperature of Pluto is unclear, but it is about 35 to 55K ( - 238 to - 218 ° C). There are five known satellites in Pluto. On July 14, 2015, NASA launched a new HOV probe to fly Pluto as the first human detector to visit Pluto. On March 4, 2016, NASA's New Horizons spacecraft project team found that the top of Pluto also covered white matter.