On Jan. 20, 2016, scientists announced the discovery of what could be a giant planet in the Kuiper Belt at the outer edge of our solar system. Nicknamed "Planet Nine," the world is a behemoth - about 10 times the mass of the Earth. It would take the planet between 10,000 and 20,000 years to orbit the sun.
Evidence for Planet Nine was unveiled by researchers Mike Brown and Konstantin Batygin at the California Institute of Technology in Pasadena, California. The scientists used mathematical modeling and computer simulations to make the find, but have not actually observed the planet directly.
The planet's existence is inferred by the orbits of six other, smaller objects in the Kuiper Belt. The orbits of those smaller objects lined up in a way that suggested the gravitational influence of another much more massive object, which Brown and Batygin dubbed Planet Nine.