I find one theory regarding Planet 9 especially interesting, and that is that it could be a primordial black hole with a Schwarzschild radius on the order of just a few centimeters. So basically, just a golf ball-sized black hole. This would explain why we can see the gravitational effects on the other objects as described in many papers, and it would also explain at the same time why we have no direct observation of this object, because it's simply too tiny and black.
I really hope this is true, because it would mean there is a black hole close enough it could be examined and studied. This might allow us to test physics ideas that can’t be tested any other way, and maybe even to “finish” physics.
It could also allow gravity and Oberth effect acceleration of small probes to meaningful fractions of the speed of light for interstellar flyby missions. Imagine the Oberth effect boost from thrusting in such a deep gravity well.
I really hope it isn't true because if there's one out there, there will be others, and I'd rather not meet one in person.
We don't have enough data to see whether there are unexpected instabilities in detected planetary systems. But it would be an interesting project to look for those.
They're not dangerous unless you get too close. A black hole is not a cosmic vacuum cleaner.
If the Moon were suddenly transformed into a tiny black hole with the same mass, it would continue to orbit the Earth at the same distance. Ocean tides due to its gravity would continue normally. There would not be much effect except that it would no longer be visible with the naked eye and would no longer reflect the sun's light back to Earth. If you found it in a telescope, you might see gravitational lensing as it passed in front of the star field. Objects like probes or old spacecraft stages orbiting the Moon would continue to do so.
The only danger would be that if things fell into it I suppose you might get dangerous X-ray and gamma ray emissions from its accretion disc that would be a problem at such a close range. That would not be an issue with a primordial black hole much further away.
If there were such an object we could send probes to orbit it and study it, and some experiments may involve firing objects or shooting lasers or beams of particles into it to attempt to learn about the quantum effects at the event horizon. This could be massive for physics, allowing us to access and observe conditions and energies not replicable here on Earth with any current technology.
BTW we don't have any hard evidence that primordial black holes exist, but many theories predict them. So far such predictions around black holes have a pretty good track record. If you made me bet, I would bet on them existing. They are a candidate for some or perhaps even all of dark matter, though even if that's not the case they might still exist. It's possible that the dark matter haloes we can spot with gravitational lensing are clouds of these things. ("Clouds" of course is a misnomer-- the distance between them would be many light years.)
If planet nine is a PBH it means that at some point one was captured by our solar system into a Kuiper Belt orbit. Even if planet nine isn't one, there still may be small asteroid mass PBHs in our solar system, so we still might find one. They would require extremely sensitive X-ray or gamma ray telescopes or highly accurate gravitational models of the solar system to detect.
It’s an object with theoretical maximum density. That’s one way to think about it.
Another visualization: if you had an Earth mass black hole with a solid shell surrounding it at the same radius as the Earth’s surface is from its core, gravity atop that shell would be 1g. The actual black hole would be about the size of a marble.
If you got close to it you would of course be subject to insane gravity and be “spaghettified” etc. All the mass would be in that marble. But at a distance it would be the same.
Compared to that object the Earth is mostly empty space. Ordinary matter is not that dense.
Black holes are totally fascinating. They are in some ways the most extreme objects that can possibly exist. If we could study one we could learn a lot.
Obviously we've managed to orbit the moon. To find the blackhole that replaced the moon just enter lunar orbit and keep firing your thrusters to slow down.
They're no more dangerous than a regular rogue planet, which are pretty common on a galactic scale. The gravitational effects (disruption to planetary orbits) are the same, and Earth would not meaningfully survive a collision with either.
I recall reading years ago some speculation that the Tunguska event may have been an encounter with such an object.
A micro black hole traveling at tremendous velocity would go right through the Earth and keep going, but as it encountered the atmosphere it might emit a bunch of ultra high energy gamma rays (due to accretion) that set off fusion reactions and create an airburst. From there it would shoot right through the Earth and cause another kaboom when it exited, but that would have been in the middle of the Pacific. Nobody would have noticed in 1908.
No way of knowing unless we find evidence in the form of a "track" through layers of rock or some other signature. A comet or other similar body remains a more likely explanation for that event.
Honestly, if there is a golf ball–sized black hole out there chilling in the outer solar system, I'm all in.
Let’s fire up a replica of TARS, load up ChatGPT inside (TARS-GPT, patent pending), and yeet it straight toward the Schwarzschild golf ball. It’ll narrate live.
Imagine the livestream:
“Approaching event horizon. Spaghettification at 3%. Mood: stretchy.”
“Entering gravitational lensing zone… wow, even my tokens are redshifting.”
Bonus: With the right timing and Oberth maneuver, TARS-GPT might sling itself into Alpha Centauri before we finish arguing whether Pluto’s a planet again.
Worst case: we lose a robot.
Best case: we unlock quantum gravity and get a podcast from inside a black hole.
Not sure why the downvotes—if I came off wrong, my apologies. I genuinely meant it in a humoristic way. I'd honestly love to see a probe launched into a black hole.
Humor devolves the site into useless one liners. If you want evidence of that, go to reddit and see how useful that site is these days if you want to actually research and learn something. Slashdot knew this back in the day and while funny posts got visibility, they did not add anything to a user's total karma score.
Oh this site does humor great, it's just that the serious participants are so "focused" they don't (or can't) realize how funny their often esoteric comments are.
As far as devolving into useless one liners --there is an emerging tech called the at-proto (not related to modems hahaa) that is poised to disrupt billions of dollars worth of sites like this one. Enjoy this era while it lasts..
Politics is mostly soft-banned (downvoted to oblivion) for a similar reason. Most political discourse online devolves into rage bait and outrage porn and people regurgitating canned talking points.
Look at Xhitter for endless examples of this, basically the whole site now.
For all it's worth, there's no need to go black hole to explain the lack of visual observation. Objects that far from a star reflect very little if any light and would appear black to a black background.
> If a black hole with a mass of, say, Ceres hit the Earth, it would not be particularly worse than if Ceres hit the Earth.
This equivalency is true for many aspects of orbital mechanics (depending on setup giving sufficient distance), but I don't believe that's true at all for a collision. Someone with more knowledge correct me, but a black hole with the mass of Ceres would be very tiny but also emitting a ton of radiation. The collision would be very different.
I more mean that the resulting moon-sized fragments of what used to be the earth would be equally devoid of life. I agree the physics might vary somewhat.
If the black hole had a mass more similar to a 0.5-mile asteroid...well, I'm not sure what would happen. Would it just punch a hole straight through the earth?
Sort of. Ceres can't turn mass into energy at a ratio that makes fusion and fusion look pretty lame.
On the other hand taking 0.00016 of earths mass, turning it into a blackhole, and shooting it through the earth isn't likely to cause nearly the damage that Ceres (100x size of the dinosaur killing asteroid) ... unless you keep the velocity low enough that it stays inside the earth.
Not at that distance but black hole starship drives are theoretically possible. Far, far beyond our capabilities but possible within known physics. This is like Kardashev type II civilization stuff.
Domesticating fusion would be much easier. That is within sight.
Yeah but you can't raise trillions of dollars with that. Investors want to be able to tell to their friends at parties that they helped made blackhole tech possible.
FWIW, the object in the linked article is visible, so while that's an interesting theory it's actually ruled out if this thing turns out to be a planet. The black hole would need to be Planet 10 I guess.
At the distances described, available passive light flux is so low, it could be 100% painted with white titanium dioxide paint and we’d be lucky to ever see it. It doesn’t need to be a black hole to be effectively invisible.
Indeed, it's a doubly inverse-squared law: one 1/d^2 factor for how far it is from the sun, by how much the solar flux is reduced; and one 1/d^2 factor again for how it is from Earth-based observers. 1/d^4, a quartic law.
That's the idea behind this paper (and similar ones like it): since they're looking for the planet's intrinsic emissions, from its internal heat, it's only a single inverse-square law.
With d being ~20 times Neptune's distance and ~140 times Jupiter's, these really are large factors!
Hawking radiation does not require an accretion disk.
Edit: with an accretion disk, I'd assume we'd have noticed it by now. Outside of that, as a black hole gets smaller, the hawking radiation wavelength should go down. It is rather weak overall, but it would be rather close. I haven't actually done the math, and, this is not my area of expertise. Would a relatively close by small black hole's hawking radiation be brighter than further X-ray emitters? Dunno.
The hawking radiation of a 9x earth mass is somewhere in the neighborhood of 0.01 K where the cosmic background is 2.7 K. It would appear to be a very tiny very cold ball.
The break even point for hawking radiation vs the cosmic background is about the mass of the moon.
I'm not going to do much more searching or calculation but I would be willing to bet a black hole small enough to emit xrays would have a remaining lifespan measured in nanoseconds at most.
A black hole bright enough to see its hawking radiation has to be tiny and would be quite short lived with an origin of unknown mechanism.
> A black hole bright enough to see its hawking radiation has to be tiny and would be quite short lived with an origin of unknown mechanism.
Depends on what distance you want to see it from.
A black hole that glows as hot as an incandescent filament would have as much mass as a 250km cube of rock and it would last for 10^35 years. It would have a radius of 60nm and emit less than a microwatt.
> a black hole small enough to emit xrays
To reach the low end of xrays, 100 electron volts, we'd need a black hole 100 times smaller. It would still have 10^29 years of lifetime, and would be emitting 2 milliwatts of xrays.
To reach the high end of xrays, 100k electron volts, we'd need a black hole 100k times smaller. It would still have 10^20 years of lifetime, and would be emitting 2 kilowatts of xrays.
To go the other way around, if I calculate a black hole that has "only" 10 billion years of lifetime left, weighing a dainty 190 million tons, it would be emitting 10 gigawatts of gamma rays. At 10 gigawatts of output, it would shrink by 1 ton every 285 years. The speed of light squared is an enormous number.
If I’m remembering right, compressing all of Earth’s mass would give a Schwarzschild radius of roughly 9 mm.
I think Uranus (15x heavier than earth) would be like basketball.
It would be extremely difficult to observe something that far away from the sun, no matter how voluminous it is. I'm not going to scorn at the idea of a blackhole, but I wonder what process can crush that much mass into such a volume. I don't think it's massive enough to suffer a gravitational collapse.
Primordial black holes can theoretically be much smaller than those formed in the usual way from collapsed stars or neutron star mergers, etc, because the early universe was dense with matter already and perturbations could have caused gravitational collapses for arbitrary volumes. I don't think we've observed any directly, which would be hard as small low-emission masses. They're still a potential piece of the dark matter missing-mass puzzle.
Primordial black holes are black holes that formed right after the big bang. Basically areas where gravity caused the extremely dense matter of the universe's first instants to collapse into black holes before expansion could pull it apart. Their existence has been hypothesized but not confirmed (or definitively rejected) so far.
A golf ball–sized primordial black hole lurking in the outer solar system sounds like pure sci-fi, but it would neatly explain the gravitational weirdness and the lack of visual detection
Any chance we could use this black hole as a really powerful slingshot by getting very close right before passing the event horizon and then firing off into space?
I think one problem for such tiny black holes is the way the gravitation works on objects that come close to it. So for instance, a spaceship could or a human could not reach the event horizon of a tiny black hole in one piece, because it would be torn apart by the gravitational tides. So the question is how close can you come to the event horizon before gravitation rips you apart. My guesstimation would be not close enough to reach a meaningful percentage of c.
