Not quite a tenth planet, but scientists have discovered a body about 3/4 the size of Pluto, orbiting the sun at a much greater distance.
It’s been named Sedna, after an Inuit Goddess. It’s also the largest object discovered within the Solar System since the discovery of Pluto.
It also has a highly elliptical orbit. It probably is nothing more than a very large object of the (theoretical) Oort cloud around the Sun.