There may also/instead be an undiscovered primordial black hole in the solar system. https://www.sciencemag.org/news/2019/09/planet-nine-may-actually-be-black-

There may also/instead be an undiscovered primordial black hole in the solar system. https://www.sciencemag.org/news/2019/09/planet-nine-may-actually-be-black-hole https://www.sciencemag.org/news/2019/09/planet-nine-may-actu...