https://www.theregister.co.uk/2018/06/05/what_planet_nine/

The mysterious, so-called Planet Nine, may not be a planet after all but just gravitational trickery, according to a new study.

A team of researchers have published a new theory explaining why objects on the edge of the Solar System like Sedna - classified as a large minor planet - have such weird, giant circular orbits. Sedna circles round the Sun at a distance of a whopping eight billion miles, making it one of the most distant objects in the Solar System, other than faraway comets.