Planet Nine is a recently discovered planet that is said to replace Pluto, which was once a planet before.  It is said it replaced Pluto because Pluto was once a planet, but they took it out of the nine planets because it was not big enough to be considered a planet, while the new planet found is way bigger than  Pluto. The planet is 5,000 times the mass of Pluto and its gravitation dominates its neighborhood of the solar system, which can explain why maybe Pluto was considered not a planet, back then in 2006. Planet Nine also has a mass about 10 times that of earth and is 20 times farther from the sun, than Neptune.

On the day of January 20, 2016, researchers at the California Institute of Technology discovered this new planet, and they said that it would take about 10,000 to 20,000 years just for the planet to orbit around the sun once.

The planet hasn’t actually been seen, but it is concluded that there is one  because of the way all the other planets are lined up in the same direction.

Scientists, Mike Brown and Konstantin  Batygin, state that even though they can not explain that there is another planet out there because it is not yet visible to see, but Planet Nine helps explain some unusual features of the field of icy objects and debris beyond Neptune. There is evidence that for the first time over 150 years, there is solid evidence that the solar system’s planetary census is incomplete, and that there is a planet out there yet to be discovered.