We all know Pluto, right? After being discovered by Sir Tombaugh back in the 1930, it was quickly labelled as the ninth planet. But after astronomers began discovering more of these mini sized objects in the outer region of Neptune, Pluto's title was then changed to Dwarf Planet. These tiny icy bodies are known to be located at the third zone of the solar system; the Kiuper Belt. It's named after Sir Kiuper who speculate about them in his 1951 research paper. Astronomers estimated that the Kiuper Belt is shaped like a donut. The content is quite similar to the asteroid belt but with additional dwarf planets. ​

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Source: https://solarsystem.nasa.gov/solar-system/kuiper-belt/overview/