For years, astronomers have bandied about the idea of a ninth planet. The theory emerged as an explanation for why objects in the outer solar system behave strangely. Some suggest that a massive planet influences these so-called Trans-Neptunian Objects (TNOs). However, a new theory posits that the culprit isn’t a planet at all, but rather a black hole, Futurism reports.
It’s a wild theory. Nonetheless, the authors of the study, published on the preprint server arXiv run by Ivy League college Cornell University, felt compelled to present their findings. Astrophysicists Jakub Scholtz of Durham University and James Unwin of the University of Illinois Chicago believe that the Sun may have captured a free-floating primordial black hole—or even a group of them.
Primordial Black Holes
So, how does the Sun capture a gravitational monster like a black hole? Why isn’t it the black hole that does the capturing? The answer lies in the type of black hole in question. Primordial black holes (PBHs) carry the moniker because cosmologists believe that they came into existence shortly after the Big Bang.
PBHs have very low mass since they didn’t form after a stellar collapse. Instead, these anomalies formed because of inconsistent densities of matter in the early universe. Denser areas are believed to have collapsed and formed PBHs.
Unlike their supermassive cousins, PBHs don’t gobble up other stars and spew the contents across the galaxy. Thus, astronomers have never directly observed a PBH.
Backyard Black Holes
PBHs may be relatively small, but they’re still black holes. Therefore, they would have no problem influencing TNOs. Furthermore, PBHs may also explain why the Poland-based Optical Gravitational Lensing Experiment (OGLE) observed an unusually high number of gravitational microlensing events.
Gravitational microlensing is basically a phenomenon where a massive object bends passing light. This tool has been useful for pinpointing black holes in the past because it takes place no matter how much light a body emits.
The fact that black holes, especially PBHs, are so hard to find brings up an interesting idea. Perhaps the reason that “planet 9” remains elusive is that there isn’t one after all. Maybe, as Scholtz and Unwin propose, the thing influencing the TNOs is actually a black hole or a pack of them. Considering that astronomers haven’t been able to find the rogue planet, the black hole theory makes sense.
So, how do astrophysicists find out if these black holes are truly responsible for influencing TNOs? Scholtz and Unwin suggest that the PBHs might make themselves known through a phenomenon called “annihilation signals.” These come from “dark matter halos” that surround black holes. If astronomers can detect annihilation signals coming from the outer reaches of the solar system, our Sun could indeed be a black hole attracting star.