Planet Nine's orbit has been discovered, and its route around the sun has been plotted by new research. The planet is estimated to have a mass of 6.2 times that of the Earth and is 300 AU from the sun.
In August 2006, the International Astronomical Union (IAU) released a controversial definition of "planet" that left Pluto out. But some astronomers were against this definition that demoted the distant orb.
In order for a celestial body to be a planet, it should become gravitationally dominant with no other celestial body close to its size except for some of its satellites which, unfortunately, Pluto cannot.