The mysterious and not-yet-discovered Planet Nine is certainly a hot topic and a new theory may even be more than strange the planet itself. The strange manner in which some distance space rocks are orbiting indicates that there could possibly be a huge world called Planet Nine that scientists have not yet found. However, according to a new research paper written by a team of scientists, the mysterious Planet Nine may actually be one of the oldest black holes in the entire universe, called a primordial black hole.
So, is it a black hole or an undetected planet? First, let’s take a look at how the Planet Nine hypothesis began. In the past few years, astronomers have discovered around a dozen objects that are acting strangely without explanation. These icy objects are called Trans-Neptunian Objects (TNOs) because they are orbiting in the distant solar system past Neptune but when they get to their closest approach to the Sun, they remain at approximately the same spot. Scientists say that it doesn’t make sense, as they are far enough away from Neptune that the planet wouldn’t have any effect on their orbits.
This is where the theory of Planet Nine comes into play, as astronomers believe that there could be a gigantic planet between 5 and 15 times the mass of Earth that is hiding somewhere in our solar system past Pluto. This huge planet is what they believe is affecting the odd orbits of the TNOs.
But, on September 24th, a new research paper was posted on arXiv that explores a new theory that Planet Nine could instead be a primordial black hole. Scientists believe that primordial black holes were first created within the first second of the Big Bang, although their existence has never officially been confirmed or denied. If the black hole theory is correct, it would mean that it would only be around the size of a baseball.
Researchers conducted an OGLE (Optical Gravitational Lensing Experiment) project over the past five years in order to find gravitational microlensing events which are when objects like a black hole passes in front of an object in the background like a star. They noticed six odd microlensing events that happened when something around 0.5 to 20 times the mass of Earth was acting like gravitational lenses. Instead of being planets, these objects could instead be primordial black holes.
According to the study, “Capture of a free-floating planet is a leading explanation for the origin of Planet [Nine].” It went on to read, “and we show that the probability of capturing a [primordial black hole] instead is comparable.”
Konstantin Batygin, who is involved with the Planet Nine hypothesis, but was not part of the new study, said that it’s possible that it could instead be a black hole although he’s not convinced. He told Astronomy, “The important thing to understand here is that all that the calculations can tell is the mass of Planet Nine, not its composition,” adding, “So, in principle, Planet Nine can be a planet, a potato, a black hole, a hamburger, etc…, as long as its orbital parameters are right.” He finished off by stating, “I always like to keep an open mind.”
Whether it’s a planet or a black hole, the theories regarding Planet Nine are always interesting and hopefully one day soon we’ll have a definitive answer as to what it actually is.