Solar System blog-post

Is Planet 9 a Black Hole?

While there are theories that planet nine is a black hole backed by groups of astronomers, including Avi Loeb at Harvard University, we do not know whether these theories will turn out to be true.



Is Planet 9 a Black Hole?

For almost 5 years, growing numbers of scientists have attributed strange orbits by objects far out in the Solar System to gravitational effects from the yet-to-be-discoveredPlanet Nine, which lies far out in the icy region beyond Neptune. Now, astronomers at Harvard University are raising the possibility that the orbital evidence for Planet Nine may possibly be a consequence of the decades-long puzzle about dark matter. Some skepticism about the Planet 9 hypothesis emerged in 2020, on the basis of findings in the Origins of the Outer Solar System survey and Dark Energy Survey.

How Big Is Planet 9?

This speculative "Planet 9" would be about 5-10 Earth-masses in size and orbit about 400-800 au from the Sun according to estimates.

In 2016, Mike Brown (who had demoted Pluto) and Constantin Batygin shocked the scientific community by publishing their groundbreaking paper proposing a planetary body at the outer edge of the Solar System. In a paper accepted for publication in The Astrophysical Journal Letters, the co-authors argue that observed clusterings of extreme trans-Neptunian objects indicate the presence of some kind of massed, super-Earth-like body at the outer edge of our solar system. Every now and then, astronomers spot the gravitational effects of an unidentified body, leading them to search for a culprit.

When Was Planet 9 Discovered?

Planet 9 has not been discovered as of this time. Researchers are currently debating the possible existence of planet 9.

Some scientists speculated that TNOs paths were being carved out by gravitational tugs from a larger body far away, one that is between five and 10 times as massive as the Earth (although others suggest the TNOs might simply be tugging at one another). TNOs are celestial bodies orbiting around the Sun, located outside of Neptune. They suggest instead that Uranuss movements are caused by an object of a mass somewhere between that of Mars and Saturn, orbiting about 200 AU from the sun.

Why Is Planet 9 So Hard to Find?

Planet 9 is so hard to find because of its hypothetical visibility and location. Due to its extreme distance from the Sun, Planet Nine would reflect little sunlight, potentially evading telescope sightings.

Instead, the astronomers said, a possible candidate is the existence of a large body, possibly the original black hole left behind after the Big Bang, but captured by the Sun. Now, new research suggests this hypothetical world may not actually be a planet at all, but rather, a black hole about as big as a bowling ball, left over from the earliest days of the Universe.

Previous studies had already shown that its Hawking radiation would be too faint to see from Earth, but new research published in January on preprint database arXiv looks at whether flyby missions have the best chances of finding the Hawking radiation emanating from such a black hole. The biggest benefit is that such a spacecraft does not have to carry its own fuel, instead sitting at the tip of a laser beam generated from Earth.

Physicists will look specifically for groups of periodic flashes of gamma-rays moving slowly through the sky, just as Planet Nine is expected to do when seen from Earth. The much-anticipated Vera K. Rubin observatory, a large telescope being built in the Andes Mountains in Chile, is scheduled to start its upcoming survey of the sky in late 2022. The TNO observations are likely biased, and therefore the astronomers might have failed to observe a proper sample, meaning that the strange bunching might have been an artifact of our observing strategy, not an actual effect.

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