From
Salon:
Hypothesis that Planet 9 is a black hole stirs controversy
Those who follow astronomy know that a scientific debate has been brewing in the past decade over the existence of so-called Planet 9, a distant, massive planet in our very own solar system. The existence of such a world has been inferred by the perturbations in Uranus and Neptunes' orbits. There's just one big problem: No one has observed Planet 9, despite being pretty sure where to look.
Now, a new scientific paper explores a very different theory: what if Planet 9 were not a planet at all, but rather a primordial black hole — a hypothetical type of small black hole that formed soon after the Big Bang, in the early Universe, as a result of density fluctuations? Such a novel idea might explain why powerful telescopes have never detected so much as a flicker from the theoretical distant, massive planet. Likewise, black holes do not emit visible light at all; rather, they absorb all photons that pass their event horizon, while occasionally emitting energy in the form of (theorized but never directly observed) Hawking Radiation.
In the paper, astronomers Jakub Scholtz of Durham University and James Unwin of University of Illinois at Chicago theorize that the elusive Planet 9 could be an old, very small black hole.
"Capture of a free-floating planet is a leading explanation for the origin of Planet Nine, and we show that the probability of capturing a PBH [Primordial Black Hole] instead is comparable," the astronomers write in the paper.
