The hypothetical Planet Nine, which is supposed to be hidden somewhere on the outskirts of our solar system, might not be a planet at all. This is what a new study published in arXiv raises, which suggests that the mysterious yet undiscovered object could be a primordial black hole and not really a planet.
The concept of a ninth planet in our solar system orbiting far beyond Neptune captured our imagination in 2016 , and earlier this year the idea gained traction again when astronomers found more scientific evidence in support of the existence of “Planet Nine.” . Now, a different team of astronomers has suggested an even more intriguing idea: that the strange body is not a planet but a miniature black hole.
The researchers consider what they describe as an “exciting possibility” that the strange motions of objects orbiting the sun beyond Neptune could be explained by the presence of a primordial black hole. As unlikely as it sounds, the authors believe that “this scenario is not unreasonable” and suggest a way to test it by looking for evidence of a microhalo of dark matter around the mini black hole.
What is a primordial black hole?
Primordial black holes represent a theoretical type of black hole formed at the origins of the universe , shortly after the Big Bang . Since the early universe was very dense, it is possible that black holes were formed not by the collapse of stars, but on a much smaller scale. These small speculative objects could weigh as little as a single time the mass of the Earth, and a black hole five times the mass of the Earth could fit in the palm of the hand, while a black hole 10 times the mass of the Earth would be about the size of a bowling ball.
That means that these black holes would be much smaller than the ones we are used to studying, so it would be possible that one was located within our solar system and that we still had not noticed.
How to find a mini black hole?
To search for the possible mini black hole in our cosmic backyard, we will have to get creative with the tools we use. Black holes absorb any light that passes beyond their event horizon, making them difficult to detect. But the researchers suggest that a planetary-mass black hole would have a halo of dark matter around it, which could extend up to 1 billion kilometers from its center. Although we cannot detect dark matter directly, we can look for dark matter particles that interact and create gamma-ray bursts that would give a clue to the presence of a black hole.
To test their theories, the researchers’ next step is to dig through data from the Fermi Gamma-ray Space Telescope, looking for telltale gamma-ray bursts that can help identify the potentially most difficult-to-reach body in our solar system.
Physicists will soon begin to analyze publicly available data from the Earth-orbiting Fermi Gamma-ray Space Telescope, which has covered the sky in all directions since 2008. They will look in particular for clusters of sporadic gamma-ray flashes moving slowly across the sky, such as Planet Nine would be expected to be seen from Earth. Although the physicists’ proposal is speculative, their search may yield all kinds of information about dark matter and the sources of gamma-ray flares, whether they are found within our solar system or throughout the universe.
Without a doubt, this fascinating work also increases the possibility that one of our neighbors is more exotic than anyone imagined.
Referencia: Jakub Scholtz, James Unwin. What if Planet 9 is a Primordial Black Hole? arXiv:1909.11090v1 [hep-ph]: arxiv.org/abs/1909.11090
