Planet Nine, also known as Planet X, is an hypothetical object in an elliptical orbit situated far beyond Pluto. Though there this object has not be observed directly, the evidence of its presence was found by researchers through the observation of its gravitational influence on other, smaller objects in its vicinity. It is difficult to be observed because of its distance from the Earth.
A new study estimates the mass of Planet Nine to be equivalent to 6.2 Earth masses. It also provided detailed insights into the orbital path of the planet. However, the location of the orbital path is unknown.