The Missing Planet

Not every planet that has been discovered was discovered by observation. The eighth planet in our solar system,
Neptune, was discovered mathematically in 1781 by observing the gravitational effects it had on Uranus. Astronomers
were able to determine the location and mass of Neptune based on how far out of orbit Uranus was pulled. Neptune
was not observed until 1846.
More recently, astronomers Jakub Scholtz and James Unwin have proposed an explanation for the wobble of objects
around and past Neptune. Past astronomers have attributed the usual wobbles in objects’ orbits to a possible ninth planet
(sorry, Pluto) in our solar system. This pair of astronomers published a paper in September proposing that the cause of
these irregularities in orbit are not attributed to a ninth planet, but a primordial black hole located between 300 and 1,000 AU
from the sun. Scholtz and Unwin propose that the black hole is a primordial black hole, a leftover from the big bang. Smaller
primordial black holes have all dissolved, but bigger ones way still exist- possibly in our solar system.
Unfortunately, such a black hole would be extremely difficult to observe. A primordial black hole with the mass proposed of
5 times that of Earth would have a radius of around 5 centimeters and would give off negligible energy. The objects distance
also means that very little light from our sun would reach it. However, this black hole would have a halo of dark matter around
it that would provide evidence of its existence. This dark matter halo would interact with dark antimatter particles and release
gamma rays that would be observable.
Scholtz and Unwin will continue on by searching for gamma rays out in the depths of our solar system, moving ever slowly
across the sky. 
So while we don't yet know whether there is a black hole or another undiscovered planet out there, we have plenty of ideas.



Nowakowski, Tomasz. “Planet Nine Could Be a Primordial Black Hole, New Research Suggests.” Phys.org, Phys.org, 30 Sept. 2019, phys.org/news/2019-09-planet-primodial-black-hole.html.
Perkins, Sid. “'Planet Nine' May Actually Be a Black Hole.” ScienceMag.org, 27 Sept. 2019, www.sciencemag.org/news/2019/09/planet-nine-may-actually-be-black-hole.

Scholtz, Jakub, and James Unwin. “What If Planet 9 Is a Primordial Black Hole?” ArXiv.org, Cornell University, 24 Sept. 2019, arxiv.org/abs/1909.11090.

Comments

  1. I absolutely love how upon opening this post, it appears to be blank but then as you highlight the words, they are suddenly revealed to us. Very Fitting for a Missing Planet

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  2. I found it very interesting to learn from your post that instead of a possible ninth planet in our solar system tugging on the farthest objects in our solar system it could be a small primordial black hole. I was wondering if it was possible or at least easier for us to view this black hole if it were real if it were to pass in front of another star, or if we were to send a satellite to its general theoretical vicinity to see if we can calculate any changes in course caused by its gravity.

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  3. Well put. I think it is cool to see how since we only see the effects gravitationally, we find it could actually be a black hole exhibiting the same effects as a planet

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