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Observations

  • The heaviest elements known in abundance in nature are forged deep within stars.

  • These elements are made possible by the high densities/pressures within the stars.

  • Black holes are known to have a much higher density/pressure than any known star.

  • Black holes are also known to be a phase of stellar evolution - this suggests that the original star's internal process of forging metals would persist within the resultant black hole.

  • Scientists have forged synthetic/ephemeral heavy metals under conditions which could hypothetically be sustained within a black hole.

Hypothesis:

Black holes forge heavier elements that have not been observed on earth. The conditions needed to sustain these elements are unique to the black hole, due to its high density/pressures. These conditions can be glimpsed, but not sustained in any experimental context

Follow up questions:

  • Has this been hypothesized?

  • Where can I find research on this topic?

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    $\begingroup$ I think you probably want to look into neutron stars, rather than black holes. The core of a neutron star is (very loosely speaking) a nucleus of a very heavy element. Like all sufficiently heavy elements, it would normally fly apart in a moment, but is held together by its own gravity and the mass of the crust of the neutron star piled on top of it. Concepts like density, temperature and pressure make sense for a neutron star, but not really for a black hole. I suggest you do dome reading (eg on wikipedia) on these subjects and come back with a more refined question. $\endgroup$ – Steve Linton Sep 30 '18 at 12:59
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    $\begingroup$ If they did then we wouldn't know. $\endgroup$ – badjohn Sep 30 '18 at 13:02
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    $\begingroup$ If, as suggested in your self-answer, you have in mind primordial black holes, then please edit your question to make this clear. Otherwise people are wasting their time explaining to you about solar-mass and heavier black holes. $\endgroup$ – Ben Crowell Oct 1 '18 at 2:14
  • $\begingroup$ See physics.stackexchange.com/questions/7131/… $\endgroup$ – Rob Jeffries Oct 1 '18 at 17:22
  • $\begingroup$ I fear you have fallen into the trap of "All A are B, therefore if some A cause C, all A must cause C" , which is of course not true. $\endgroup$ – Carl Witthoft Oct 1 '18 at 18:08
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The heaviest elements known in nature are forged deep within stars.

No, the heaviest elements are made on Earth in scientific laboratories, or in the extreme gravity of a neutron star's crust.

These elements are made possible by the high densities/temperature/pressures within the stars.

Many of the larger elements can be made in supernovae and neutron star collisions, not in stars. It requires extreme conditions for these elements to form.

Black holes are known to have a much higher density/temperature/pressure than any known star.

Black holes are actually very cold, they "absorb" any radiation that passes their event horizon. Outside the event horizon may be some very hot material, but it is not actually so hot compared to the core of a star.

Black holes are also known to be a phase of stellar evolution - this suggests that the original star's internal process of forging metals would persist within the resultant black hole.

No, inside the black hole everything falls, and reaches a singularity in a short amount of time.

Scientists have forged synthetic/ephemeral heavy metals under conditions which could hypothetically be sustained within a black hole.

As above, the conditions beyond the event horizon are unlike anything we have on Earth, because there is the unavoidable singularity.

After some matter has crossed the event horizon it will certainly come to the singularity. (in the same way as you will certainly reach tomorrow) And as it gets closer the tidal effects get greater, eventually ripping the atoms apart. The extreme gravity in a black hole will tend to pull matter apart not fusing it to larger atoms.

There may be nucleosynthesis in the accretion disc around a black hole. While the amount of high mass atoms made here is relatively small, it may be useful for the sake of detecting and distinguishing black holes from neutron stars or white dwarfs.

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    $\begingroup$ Also may be worth pointing out we don't know what happens at a singularity because they're all inside black holes we can't see into. (We can predict, but our predictions are based on models that weren't designed with any data from singularities) $\endgroup$ – immibis Oct 1 '18 at 1:56
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    $\begingroup$ @Mehrdad But why... It certainly CAN happen, but it will not last. Ice doesn't spontaneously appear in a boiling kettle even if it CAN. Iron is the element where you gain no energy from fusion, nor from fission. It is the final destination for any nucleosynthetic equilibrium. Only in non-equilibria processes will you find elements heavier than iron (i.e: violent explosions, or specifically designed particle jets...) $\endgroup$ – Stian Yttervik Oct 1 '18 at 11:14
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    $\begingroup$ @mehrdad if the atoms were moving fast enough to fuse, the resultant atom is also moving fast enough to undergo fission. Not that "moving fast enough" is the proper description, but using your words for comprehension $\endgroup$ – Stian Yttervik Oct 1 '18 at 15:50
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    $\begingroup$ @Mehrdad that's because it isn't true. physics.stackexchange.com/questions/7131/… $\endgroup$ – Rob Jeffries Oct 1 '18 at 17:23
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    $\begingroup$ @StianYttervik Elements heavier than iron are formed inside stars (known since the 1950s). The reason that they don't form by fusion is that at the temperatures required to tunnel through the Coulomb barrier they are also vulnerable to photo-disintegration. Not fission. $\endgroup$ – Rob Jeffries Oct 1 '18 at 17:28
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Superheavy elements have short half lives because of their extreme instability with respect to alpha decay and fission. This is a result of their high electric charge, which results in strong forces of electrical repulsion. Although theorists have predicted an "island of stability" due to quantum mechanical shell effects, this stability is a relative thing. We're still talking about half-lives on the order of seconds or less. So any such element created by astrophysical processes will not survive for very long, even if it doesn't fall into the black hole.

So conceivably in the accretion disk, outside the event horizon, you could get some fusion events resulting in the formation of superheavy elements, but those elements would not survive for very long, even if they were somehow ejected rather than infalling past the horizon. And the normal methods for detecting and characterizing superheavy elements would not work here. Normally we look for things like alpha-decay chains with characteristic alpha energies. Those would not be detectable from outside the accretion disk, since charged particles interact strongly with matter and are stopped.

The conditions needed to sustain these elements are unique to the black hole, due to its high density/pressures.

Most of the interior of a black hole (inside the event horizon) is probably an extremely good vacuum. The only high densities and pressures would be near the singularity. So any exotic matter formed at high densities and pressures would not be observable from earth or have any consequences for the outside universe, because nothing can escape from inside the event horizon.

If we were to send a space probe inside a black hole to look for exotic matter being formed near the singularity, the probe would not be able to report its results back. Also, the region of high-density and high-pressure infalling matter would exist near the singularity, which would probably not be detectable to the probe until the probe itself had been destroyed by the same processes. (On the inside of a black hole, if general relativity is correct, you can't see the singularity. You only see infalling photons from the outside.)

If exotic matter is formed near the singularity, it will only exist for a very short time before accreting onto the singularity. (IIRC the maximum infall time for a 10-solar-mass black hole is on the order of milliseconds from horizon to singularity.) We don't really know what happens at the singularity, but we certainly can't have atomic nuclei under those conditions.

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    $\begingroup$ milliseconds from which frame of reference? $\endgroup$ – Michael Oct 1 '18 at 3:18
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    $\begingroup$ @Michael: Milliseconds of proper time, i.e., the time on a clock that is infalling along this trajectory. The proper time for free fall from horizon to singularity for a Schwarzschild black hole is equal to the Schwarzschild radius over $c$, multiplied by a unitless constant of order unity. (The exact value of the unitless constant depends on the state of motion as you pass the event horizon. Starting from rest at the horizon is only possible in the sense of a limit.) $\endgroup$ – Ben Crowell Oct 1 '18 at 15:26
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The problem of the superheavy elements is not that we can't forge them. Their problem is that they decay very quickly. For example, Oganesson, the heaviest element synthetised until now, has a half life of 181 ms.

In theory, even much heavier elements could be created in particle accelerators, but there is no way to even detect them.

In neutron stars, or in exploding supernovas, all the elements are created, but there is no way to even detect them. We can consider a neutron star as a large nucleus with $\approx 10^{56}$ neutrons.1

In black holes, the fact is that no one knows, what is in them. They don't radiate anything (with a very little exception), and nothing leaves the singularity in them. To understand what is in them, would require currently unrealistic advances in Physics. The singularity in their center is probably not baryonic matter, though, thus we could hardly say that it would be any chemical element.

1As @PM2Ring's excellent comment says, neutron stars also have a significant number of other particles, too, not only neutrons. I also extend it that they are bound gravitationally and not by the strong interaction, which makes them in this aspect essentially different from nuclei.

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    $\begingroup$ Thanks for your perspective - there is a small misinterpretation which I should clarify better. I didn't suggest that we have a problem in forging the heavier metals. I hypothesized that black holes forge heavier elements, which have not been observed yet. I also suggested that the internal processes of the black hole might be best informed by that of its preceding star, namely the process of forging heavy metals. I then asked if this has already been hypothesized, and for references to any existing research. $\endgroup$ – efreezy Sep 30 '18 at 13:39
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    $\begingroup$ I think you mean "soup", not "soap". FWIW, a neutron star isn't pure neutrons. They are hypothesized to have a layered structure, with an outer crust consisting of relatively normal heavy atoms that transitions into a mixture of such nucleons and neutronium, pure neutronium, and possibly some exotic quark matter in the core. However, even pure neutronium is not solely composed of neutrons. It's a dynamic substance that also contains some protons (and electrons) with the concentration of protons ranging from around 10% to 1%, depending on pressure. $\endgroup$ – PM 2Ring Sep 30 '18 at 22:51
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    $\begingroup$ Virtually every sentence of this answer contains mistakes. The problem of the superheavy elements is not that we can't forge them. Their problem is that they decay very quickly. No, the problem is that we can't forge them. We lack appropriate beam-target combinations, and the cross-sections are extremely small. For example, Oganesson, the heaviest element synthetised until now, has a half life of 181 ms. This would be some isotope of that element. The half-life is a property of the isotope, not the element. $\endgroup$ – Ben Crowell Oct 1 '18 at 1:40
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    $\begingroup$ In theory, even much heavier elements could be created in particle accelerators, but there is no way to even detect them. Not true. Superheavy elements are often extremely easy to detect once formed. Typically the recoiling nuclei are allowed to fly out of the target to a detector, which detects alpha decays. In black holes, the fact is that no one knows, what is in them. I guess this depends on what you mean by "know." We certainly have theories that can predict this. However, the region inside the event horizon is causally disconnected from the outside universe. $\endgroup$ – Ben Crowell Oct 1 '18 at 1:42
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    $\begingroup$ nothing leaves the singularity in them. What is more relevant is that nothing gets out past the event horizon. The singularity in their center is probably not from baryonic matter, tough, thus we could hardly say for that it would be any chemical element. No, the singularity is expected to have almost all of its mass originating from baryonic matter. $\endgroup$ – Ben Crowell Oct 1 '18 at 1:44
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Instead of diving into misdirected debates and bike-shedding, I will answer my own question here with clarity, coalescing some of the useful feedback I've received thus far.

Question

Could Black holes forge heavier elements that have yet to be discovered? Has this been hypothesized? Where can I find research on this topic?

Answer

Yes, and it is hypothesized that they do as they interact with and consume other celestial objects.

Research performed last year at Cornell suggests that some or all of the inventory of r-process nucleosynthesis can be produced in interactions of primordial black holes (PBHs). In nuclear astrophysics, R-process capture is responsible for the creation (nucleosynthesis) of approximately half the abundances of the atomic nuclei heavier than iron.

Feel free to take a look at that research here: https://arxiv.org/abs/1704.01129

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    $\begingroup$ That abstract from Cornell talks about nucleosynthesis from neutron star matter spun off the exterior of the NS in response to internal collapse caused by a PBH. They are not claiming that the nucleosynthesis would occur in the immediate vicinity of the PBH, nor that the species produced would be outside the standard inventory of nuclei. A PBH is not a stellar remnant, it's primordial, and we have no good evidence that they exist; the linked article is basically saying that if the process they describe is observed then that could be interpreted as evidence for PBHs. $\endgroup$ – PM 2Ring Sep 30 '18 at 22:31
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    $\begingroup$ (cont) The last 2 sentences of that abstract mention several observations that are consistent with their speculated NS-PBS destruction scenario, not that those observations can only be explained by that scenario. The thrust of that paper is that PBHs might exist, and thus should be considered as a possible component of dark matter. Note that mainstream theory considers the existence of PBHs as very unlikely, due to lack of evidence in other searches that have been conducted. $\endgroup$ – PM 2Ring Sep 30 '18 at 22:39
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    $\begingroup$ I'm not discrediting their hypothesis, just adding some qualifications to it, and clarifying some points in it that you appear to have misinterpreted. We know that NS events can give nucleosynthesis, the recently observed NS collision gave us evidence of that. Your question asks about nucleosynthesis by BHs, that article is about nucleosynthesis by NS matter that could be triggered by PBH-induced NS collapse, the BH is not directly involved in the nucleosynthesis reactions. It's even more indirect than nucleosynthesis that occurs in the accretion disk of a regular BH. $\endgroup$ – PM 2Ring Sep 30 '18 at 23:01
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    $\begingroup$ If you had in mind primordial black holes, it would have been helpful to state that in the question. Primordial black holes are not known to exist. The paper you linked makes calculations that are conditioned on the existence of a certain number of primordial black holes. The paper also says nothing about superheavy elements. $\endgroup$ – Ben Crowell Oct 1 '18 at 2:12
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    $\begingroup$ -1. Your question asked "Could Black holes forge heavier elements that have yet to be discovered?" but your answer fails to provide any evidence about this. Have you read the article you linked to? Nowhere does that article suggest the creation of undiscovered or superheavy elements. $\endgroup$ – Chappo Oct 1 '18 at 4:40

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