Planet 9 Might Be a Black Hole

The weird orbits of Trans-Neptunian Objects (TNOs) and an excess amount of microlensing events in the 5-year OGLE dataset can be simultaneously explained by a new population of astrophysical bodies with mass several times that of Earth. Researchers propose that these objects to be primordial black holes (PBHs) and point out the orbits of TNOs would be altered if one of these PBHs was captured by the Solar System, inline with the Planet 9 hypothesis. Capture of a free floating planet is a leading explanation for the origin of Planet 9 and we show that the probability of capturing a PBH instead is comparable. The observational constraints on a PBH in the outer Solar System significantly differ from the case of a new ninth planet. This scenario could be confirmed through annihilation signals from the dark matter microhalo around the PBH.

The orbits of trans-Neptunian Objects (TNOs) have been taken as evidence of a new ninth planet in our solar system, called Planet 9 (P9), with mass about 5 to 15 times the Earth and they would be orbiting around the Sun at a distance of 300−1000 AU. There is set of gravitational anomalies recently observed by the Optical Gravitational Lensing Experiment (OGLE). OGLE reported an excess of six ultrashort microlensing events with crossing times of 0.1 − 0.3 days. The lensing objects are located towards the galactic bulge, roughly 8000 parsecs away. These events correspond to lensing by objects of mass of half of the Earth to 20 times the Earth. They could be interpreted as an unexpected population of free-floating planets (FFPs) or as Primordial Black Holes (PBHs).

These two anomalies correspond to a similar mass scale. Perhaps the most natural explanation is that they are caused by the existence of an unknown population of planets.

However, IF the OGLE events are due to a population of PBHs then it is possible that the orbital anomalies of TNOs are also due to one of these PBHs that was captured by the Solar System.

There are three alternative hypotheses for the origin of Planet 9:
a) P9 formed on its current orbit (‘in situ’);
b) P9 formed in the inner Solar System and has been up-scattered into its current orbit; or
c) P9 has formed outside of the Solar System and has been captured.

While all three scenarios are unlikely, they are still favorable compared to the chance alignment of TNOs. In case of the in situ formation, at a ∼ 500 AU there is typically insufficient time and material to build an Earth mass planet. The prospect of a planet forming near Uranus and Neptune before being scattered to its present orbit is low since in order to fall into a stable orbit the planet would need to be appropriately influenced by a passing star (or another mechanism) [4, 29]. The probability of capturing a free-floating planet (FFP) is estimated to be similarly improbable, with estimates differing by orders of magnitude depending on assumptions.

The anomalous orbits of TNOs and OGLE’s short microlensing events could have the same origin. They could be caused by a population of Primordial Black Holes with five times the mass of the Earth. While the principal search strategies for a planet is to employ optical and infrared/microwave surveys, the signals could be very different for a PBH (or another exotic object). Thus, the PBH hypothesis expands the required experimental program to search for the body responsible for TNO shepherding and motivates dedicated searches for moving sources in x-rays, gamma rays and other high energy cosmic rays. Conversely, if conventional searches fail to find Planet 9 and the evidence for TNO anomalies continues to grow, the PBH P9 hypothesis will become a compelling explanation.

Arxiv – What if Planet 9 is a Primordial Black Hole?

Written By Brian Wang,

42 thoughts on “Planet 9 Might Be a Black Hole”

  1. I doubt it. They need to look harder for it. What they need is more telescopes and telescope time.

  2. It would have at best no greater tendency to capture stuff then the same mass planet – things could fly past it at distances much less than a normal planet radius, and just go through empty space and back out.

    Also, it’s believed to be in a large orbit (400-800 AU semi-major axis) with 10000-20000 years orbital period. That’s long enough for it to have been close to aphelion, in relatively sparsely occupied space, throughout all of recorded history.

    That being said, if interactions between nearby objects did occur, stuff could be captured into orbit around it. Moons around the black hole at normal orbit sizes would not have any particular tendency to be unstable and decay into the black hole, but small stuff captured really close in could hit each other and fall into an accretion disk and release a lot of energy eventually. But the effective radius for such captures that would release such energy might be quite small.

  3. No one is trying to produce controlled nuclear fusion by the means that is said to occur in the center of stars including the sun. that is by gravitational compression. When we finally get electricity from nuclear fusion it is more likely to be from electrical z pinch being pursued by the plasma physicist Eric Lerner with less money and attention than the ways you read about. This method supports the plasma universe model instead of the gravity only model.

  4. Why would a black hole of mass about 5 to 15 times the Earth disturb the Oort cloud any more than any other object of the same mass?

  5. So the debate is REALLY the exact details of the description of the thing described by the common phrase “black hole”.
    Not whether they actually exist or not.

  6. It woyud have already been detected or if it did exist affect our solar system more than a minor blip to our planets. Oort cloud would have already dissapeared, so on and so forth. Highly probable it’s not there. Disturbance could be the effect of a giant wandering planet that passed through the edge of our solar system at a certain inclination a long time ago. We haven’t settle from the affects of it yet.

  7. Or a mothballed death star production plant, ready to be reactivated if those apes on the inner planets start to look threatening.

  8. This, added that the solar system has 2 Neptune sized objects who was not discovered until modern times.
    Planet X farthest away from the sun, have fun spotting it.

    I say its an abandoned death star production plant.
    They would not show up more that any boring super earth or Neptune style object.

  9. Come on Brett. You know perfectly well that the events you can never know about are always the most interesting.
    The parties you will never be invited to.
    The clubs that don’t even acknowledge their existence, let alone accept you as a member.
    The books that your local library will never stock.
    The doors you must not open.
    The path less travelled.

  10. Yes, I’d say that having a black hole close enough for use to send probes to it within our lifetimes (say this century at the outside) would result in science being a lot more advanced in 2200 AD than otherwise.

  11. “There are far more interesting things happening inside the event horizon, than just light not escaping.”

    That’s where Dave’s complaint starts to have some bite; Why do you think there are interesting things happening in a region you can’t ever have knowledge about?

  12. Dont be a wimp. We could obtain enough rotational energy from a nearby pbh to power our civilization for just this side of forever.

  13. It would still be detectable by other processes, all of them generating odd signatures. There would be xray emissions and jetting due to accretion. Over time it would capture things in its orbit, which would be in unstable orbits, collide and generate accretion disk. Outer Solar system is too crowded for a dense object to be undetectable for the duration of astronomical history.

  14. its not a black hole… its a worm hole for alien visitors… sheeshh…doesn’t this guy watch ancient aliens?

  15. An accretion disk has been photographed — I’m not purporting BHs don’t exist, but what was photographed certainly doesn’t prove that BHs as described mathematically definitely exist.

  16. This is a sort of confusing statement – I think I know what you mean, but it’s misleading. Newtonian mechanics doesn’t have a concept of a fixed value of c. If it did, what you describe would be true — such a body of mass could exist such that light cannot escape the gravity well. However, nothing about Newtonian mechanics requires there be a fixed value of c. That came later in the Michelson Morley experiment and obv, later Special Relativity. But if you had some concept of a fixed value of c in Newtonian physics, then yes.

  17. No, it cannot increase ‘without bound’, but it can increase asymptotically as time goes to infinity. It’s proportional to the inverse square of v/c, so the dilation will asymptotically approach 1/infinity (in this paradox).

  18. I know what he’s talking about; it’s basically the paradox that GR presents to us that, as matter compresses further and further closer to an event horizon, it suffers time dilation to such a degree that it cannot ever reach the event horizon in finite time as measured by an observer at infinity, although it does pass the event horizon and reaches the singularity in finite proper time.

    So the idea he’s advocating is that there are no such things as black holes; there are celestial objects perpetually frozen in mid-collapse as time dilation increases without bound (can it increase without bound?). The light emitted just before the event horizon forms only reaches outside observers after infinite time, and we haven’t had that duration elapse yet since the big bang.

    The upshot is that, even though the singularity in Sagittarius A* (or whichever other black hole) does not exist yet, we still have an object which, to a distant observer, has all the properties we attribute to black holes today.

  19. If a planetary body did form from the prior Pop II star in our local region, it would be significantly cooler in black body temperature since its origin was >4.8B years.

  20. Has anyone given thought to the possibility that planetary bodies were formed from the previous star (pop II) that existed in our region of space that went supernova and generated all of the metal that eventually coalesced into the Sol System? The sun’s predecessor would have been very large and any metal-poor planetary bodies would have formed much further away >100AU. I have had a suspicion that the groupings of some of these TNOs are from the “older” disk from the previous star in the center-of-mass system.

  21. I find it hard to believe that there’s a substantial population of primordial black holes, because this would imply stars being consumed in collisions with them, often enough to be noticeable. The observed lifespan of stars places a fairly stringent ceiling on the population of such objects.

    It’s dark enough out there for normal objects in that size range to go unseen.

  22. Black holes basically have to exist, unless there’s some unknown physics that prevents it; All they are is objects with an escape velocity higher than the speed of light, which are inevitably going to turn up even under Newtonian physics.

  23. i’d argue it would even be a good thing! Imagine all the data we could get by sending a probe there! Juicy new physics!

  24. Why not? Besides being hard to see, its no more dangerous than a planet of equivalent mass. One could argue that it’s safer, since you have to get closer to it for it to affect you.

  25. No proof PBHs even exist, but it would be very cool if confirmed. PBHs are also a possible “MaCHO” dark matter candidate. My understanding is that MaCHOs have been largely ruled out though.

  26. The article mentions objects “with mass several times that of Earth”, so at least 1E25 kg. The luminosity through Hawking radiation for a black hole of this mass is about 3.56E-18 Watts, far too small to be detected. Even a pluto-mass black hole wouldn’t register. It would need to be much smaller to shine bright enough to be detectable, but then it wouldn’t be a planet 9 candidate.

  27. It’s probably a slowly-aggregating strangelet, and we’re all doomed. I await my impending nuclear transformation.

  28. Problem with the small blackhole idea in Solar system is the instabitily of small blackholes, especially in case of a primordial one. Small blackholes have to evaporate via emission of radiation, which would make them look more like a star rather than an invisible object detectable only by microlensing. That would be detected long ago, as a fast-moving star in orbit around Sun.

    The idea can be saved if the blackhole (or rather a dense object) is something else, without event horison. Neutron star would be unstable at that mass. More exotic matter may always explain things away, except for one: its origin. Hence a cold dark planet is still the most plausible candidate. Oh, there is always dark matter handy, and some unexplainable lump would explain the microlensing, but good luck detecting it to prove that hypothesis. 🙂

Comments are closed.