What If Planet Nine Is a Bowling Ball-Size Black Hole?
By Ryan F. Mandelbaum
Planet 9 Could Be an Ancient Black Hole Orbiting the Sun
By Morgan McFall-Johnsen
What If Planet 9 Is Actually a Tiny Black Hole?
By Ryan Whitwam
Planet Nine could be a primordial black hole, new research suggests
By Tomasz Nowakowski