By Suri Sanchez
Scientists have been running new computer models and it found Planet Nine. Planet Nine is also being called Planet X. It was discovered last year, so there isn't a lot of information about the planet yet. The crazy thing about Planet X is that scientist haven't seen it yet! They think the reason they haven't seen it is because it may be hiding way behind Pluto. Researcher Alexander Mustill says maybe that the planet nine came from outside of the solar system so it might be an exoplanet. They have also noticed that the orbits of other objects are a bit unusual so Planet X might explain that.
Planet Nine takes about 10,000 to 20,000 years to make one orbit. Planet Nine is believed to be 10 times the mass of Earth. It is about the size of Neptune.