I think “15 times further from the Sun than Pluto” is more meaningful for most readers than “700 times further from the Sun than Earth.” If it exists, it’s way way way out there.
The rest of the planets are theorized to have condensed from the protoplanetary disk that formed the same molecular cloud the Sun did. I. e. they have formed at approximately same time as the sun and from same material, sans gravitational separation.
The other planets formed from material in the same nebula (cloud of gas and dust) that collapsed to form the sun. The idea here is this planet would have been moving through the interstellar medium and just happened to pass close enough to the sun’s gravity well to get captured in a (very distant) orbit.
Capture would be like a reverse gravitational slingshot? This planet happened to meet the sun at an angle where it lost enough energy to fall into orbit instead of slinging back out like those comets that come around on long cycles?
AFAIK, it could be in a 2 bodies slingshot, multi-body interaction with some other stuff on the Oort cloud, or tidal interaction (what could happen way more easily with a nebula).
Not true. An obit is not an infinite "plain" with a finite "hill" on but rather a finite "valley". The ball will exit the valley on the other side unless it loses excess kinetic energy somewhere in the valley.
My favorite: Cody'sLab's "How far away are the nearest stars": https://youtube.com/watch?v=dCSIXLIzhzk
Also gives an intuition for how incredibly bright stars shine
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.
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!
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.
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.
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.
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.
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.
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.
If those two spots are the same object, that object is on a high-inclination orbit; but the pattern the Planet 9 hypothesis explains is only compatible with a low-inclination object.
His team discovered Eris and many other trans-neptunian objects, which did fuel the discussion behind pluto's demotion: greatly increase the number of planets, or demote pluto? They're also behind the Planet 9 theory that's discussed in the article.
we already have a 9'th planet, but due to the greatest pedantic campain of all time, pluto got demoted. Though given the current situation, ha!, that could change.....perhaps the naming commity will get noticed, and be offered a chance to do a deal, and Make Pluto A Planet Again,(MPAPA)
We should add those planets to the official list too. Gauss considered Ceres to be a planet and I believe him over living astronomers.
The motivation for this dwarf planet nonsense was to try to keep the official planet list small so children could memorize them with ease, but that is absurd. We do not remove countries from the map to make it easier for children to learn geography and there are over 100 of them.
If planets are required to clear their orbits, what was Jupiter called while the solar system was forming? A dwarf planet? A proto planet? The entire time?
Was earth not a planet shortly before and after collision with Theia?
The naming pedantry seems ridiculous given that we have such a small sample size.
Every single definition that segments a real world set of continuous objects into discrete buckets has surprising edge cases. This is basically inescapable.
To steal a quote: All definitions are wrong. Some are useful.
I find that to be the most weird one too. I don't know much about orbital mechanics but in the unlikely chance 2 bodies shared an orbit does that mean they aren't planets then? How close can two planets be before losing that designation? I share your ire.
The definition is pretty arbitrary. It's more interesting, what can we learn by studying that object. Even the trivia, like tidal locking, it was one of my 10000 moments (https://xkcd.com/1053/).
I think “15 times further from the Sun than Pluto” is more meaningful for most readers than “700 times further from the Sun than Earth.” If it exists, it’s way way way out there.
Yes, also being 10x the mass of Earth that far out hints that it may be an interstellar object captured by the Sun.
Forgive my ignorance but how is that different than the rest of the planets?
The rest of the planets are theorized to have condensed from the protoplanetary disk that formed the same molecular cloud the Sun did. I. e. they have formed at approximately same time as the sun and from same material, sans gravitational separation.
Ah, so a captured body would be quite different and alien. Really old too. Like, first generation of stars.
Not at all implied. It could be boring and younger too.
10x earth masses usually implies a gas giant.
The other planets formed from material in the same nebula (cloud of gas and dust) that collapsed to form the sun. The idea here is this planet would have been moving through the interstellar medium and just happened to pass close enough to the sun’s gravity well to get captured in a (very distant) orbit.
Capture would be like a reverse gravitational slingshot? This planet happened to meet the sun at an angle where it lost enough energy to fall into orbit instead of slinging back out like those comets that come around on long cycles?
AFAIK, it could be in a 2 bodies slingshot, multi-body interaction with some other stuff on the Oort cloud, or tidal interaction (what could happen way more easily with a nebula).
A comet coming back on a long cycle is an orbit
gravitational capture
You don't need to lose energy to enter orbit any more than you need to lose energy too roll a ball down a hill.
Not true. An obit is not an infinite "plain" with a finite "hill" on but rather a finite "valley". The ball will exit the valley on the other side unless it loses excess kinetic energy somewhere in the valley.
Correct, but my point is you don't need to lose energy to enter orbit.
You don't need complex reverse slingshot interactions. You just need a low enough relative velocity to not shoot off the other side.
I would expect this to be the norm for capture, not some exotic phenomenon.
A ball doesn't need to lose energy to roll down into a valley either.
There's an episode on "Space & Beyond" where they show all the planets in scale to the realworld on an actual football field.
Then to show Planet 9 distance they have to get in a car and drive a few miles.
That worked for me.
My favorite: Cody'sLab's "How far away are the nearest stars": https://youtube.com/watch?v=dCSIXLIzhzk Also gives an intuition for how incredibly bright stars shine
I think Bill Nye has something similar, too.
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.
If it were earth mass it would be ~grapefruit size. This estimate puts object nine at 9 earth mass so maybe vollyball size or melon size? https://www.astronomy.com/science/is-planet-nine-a-black-hol...
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!
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.
Not sure I want a black hole in my backyard ;-)
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.
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.
Running into a rogue black hole must be far less likely than an extinction level impact with a relstively boring big rock.
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.
That is very interesting and made me realize I did think of black holes as “sucking” things in. Which I see is not the right way to think about it.
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.
That's Newton's Shell Theorem for you.
We could use the black hole to power our civilization due to how efficient it is for generating power.
No need for something that exotic. The Earth alone receives more energy from the sun every hour than mankind uses each year.
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.
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.
I'd call that a win.
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.
This cannot be evidence of Planet 9 (the Batygin and Brown hypothesis)—it's outright incompatible with it.
https://bsky.app/profile/plutokiller.com/post/3lnqm2ymbd22r
If those two spots are the same object, that object is on a high-inclination orbit; but the pattern the Planet 9 hypothesis explains is only compatible with a low-inclination object.
The guy killed Pluto and still he isn't done :(
Seriously though, is he one of the people responsible for Pluto's demotion to dwarf planet?
His team discovered Eris and many other trans-neptunian objects, which did fuel the discussion behind pluto's demotion: greatly increase the number of planets, or demote pluto? They're also behind the Planet 9 theory that's discussed in the article.
Nah, if it is big, and at that distance, and follows an elliptical orbit then yes it will be "Planet 9^W 8"
I hope this turns out to be wrong. I’m still holding out for a primordial back hole Planet X. That would be soooo cool and unbelievably useful.
Why useful? Considering how hard of a time astronomers are having to simply find it it’s hard to imagine it being easy to study.
Original paper: https://arxiv.org/pdf/2504.17288
Non-PDF link: https://arxiv.org/abs/2504.17288
we already have a 9'th planet, but due to the greatest pedantic campain of all time, pluto got demoted. Though given the current situation, ha!, that could change.....perhaps the naming commity will get noticed, and be offered a chance to do a deal, and Make Pluto A Planet Again,(MPAPA)
If you add Pluto, you must add also Eris and a few more, like 5 or more, and perhaps also Ceres.
Here is a nice graphic that excludes Ceres https://en.m.wikipedia.org/wiki/Dwarf_planet#Population_of_d...
I would add those to the list of official planets, yes. Don’t remove Pluto, add the rest.
So that makes Pluto the 10th planet an Neptune the 9th planet.
We should add those planets to the official list too. Gauss considered Ceres to be a planet and I believe him over living astronomers.
The motivation for this dwarf planet nonsense was to try to keep the official planet list small so children could memorize them with ease, but that is absurd. We do not remove countries from the map to make it easier for children to learn geography and there are over 100 of them.
I mean… there has to be more to it than that right? But im also open to being red pilled on pluto.
The same happened to Ceres first. To be fair, Make Ceres A Planet Again!
If planets are required to clear their orbits, what was Jupiter called while the solar system was forming? A dwarf planet? A proto planet? The entire time?
Was earth not a planet shortly before and after collision with Theia?
The naming pedantry seems ridiculous given that we have such a small sample size.
Every single definition that segments a real world set of continuous objects into discrete buckets has surprising edge cases. This is basically inescapable.
To steal a quote: All definitions are wrong. Some are useful.
I find that to be the most weird one too. I don't know much about orbital mechanics but in the unlikely chance 2 bodies shared an orbit does that mean they aren't planets then? How close can two planets be before losing that designation? I share your ire.
Yes, Pluto is the tenth planet.
To discover Planet 9, simply open your ephemerides and look for "Neptune".
Ya, I know but Ceres is going to get pushed into an intersection with Mars to generate an atmosphere and a hydrological cycle .......testing on fusion rocket drives is ongoing https://newatlas.com/space/pulsar-fusion-rocket-design-slash...
I mean, if you’re pushing ceres around, teller and ulam already designed the ideal fusion rocket
Pluto for planet! https://www.planetarium-hamburg.de/en/pluto-for-planet
This is especially important if it turnes out there is a black hole acting as an additional planet, since it justifies the “Planet X” name.
The definition is pretty arbitrary. It's more interesting, what can we learn by studying that object. Even the trivia, like tidal locking, it was one of my 10000 moments (https://xkcd.com/1053/).