After seeing articles about the JWST like these two: https://news.cornell.edu/stories/2023/02/astronomers-discover-metal-rich-galaxies-early-universe


And some older articles like this one: https://www.salon.com/2021/11/18/gold-black-holes/#:~:text=According%20to%20the%20new%20paper,occur%2C%20which%20creates%20heavy%20metals.

I thought: "Wouldn't the birth of primordial supermassive black holes during the big bang create a bunch of heavier elements as it ate and fling them all over the place?"


If the density was sufficient enough early enough in the process of the big bang to form a macroscopic black hole, then it may also have had sufficient mass and enough surrounding dense gases to form a metal-producing accretion disk.

I guess the question then becomes: "How early in the big bang process could a black hole accretion disk have formed? Also, could such an accretion disk in that environment be capable of forming heavier elements from the hydrogen and helium surrounding it?"


1 Answer 1


I am a new user so if you find any error in my answer kindly correct it.

Perhaps, but indirectly

Heavier elements are made in nuclear furnaces, where processes such as nucleosynthesis/neutron capture processes i.e slow and fast

In primordial black holes (a type of micro blackhole), there are no physical processes that take place inside the blackhole which will form heavier elements.

In the early universe where everything was a soup of plasma, the extreme heat and the comparatively tiny universe, acted like a star, so early primordial nucleosynthesis happened to create hydrogen and helium (and a few traces of heavier elements e.g lithium), and once the universe cooled down, no more primordial nucleosynthesis happened and therefore the values of abundances of elements stayed fixed until the first generation of stars/population III (low metallicity stars) were born.

The first point made that even the primordial blackholes ate the primordial plasma, Virtual particles and CMB is spot on

The second point, that it will fling it is also correct but the flinging which I think is about Hawking radiation, which is that absorbing a pair of virtual particles will cause one of the particles to have negative energy while the other one escapes and the negative energy destructs the singularity (if there is one, because quantum gravity, ruling the early universe doesn't prefers singularities).

and Hawking radiation would tear the matter into pieces that are subatomic particles like protons and neutrons and expel it (causing loss of information. Refer to the Information paradox), but the main point is that the energy of Hawking radiation in the case of the smallest primordial blackholes called planck relics (Blackholes with the schwarzchild radius equal to the Planck length) are 3.562×10^48 watts thereby converting 100% of the mass to energy which is a huge amount of power and has the potential to heat it's surroundings (unless it is in thermal equilibrium) and thus causing nucleosynthesis (also the nucleons expelled may have collided with other atoms causing heavier elements to form) so it has the potential to create heavier metals outside the blackholes (outside the event horizon) due to the energy supplied by hawking radiation rather than inside the blackhole though the matter fallen in may or may not.

So the hypothesis is not entirely wrong but the point that the black hole is the nuclear furnace is wrong instead the expulsion may have caused the nucleosynthesis rather than the blackhole itself so heavier elements may have formed indirectly (plus it would not have increased the mettalicity drastically).

Or else if by flinging you mean by shooting matter out of the accretion disk, the chances are rather high because if the rare accretion disk on PBH is formed by devouring population III/first-gen stars (which were formed early), it may have caused nucleosynthesis because the accretion disks are insanely hot, and if the trajectory, is finetuned then the metal-rich elements could have escaped from the blackholes

Also, PBHs on the heavier side may have infested neutron stars and have created heavy metals

  • $\begingroup$ Kindly leave a comment or a vote for me to improve my answer. Thanks! $\endgroup$
    – Arjun
    Jul 2, 2023 at 9:46
  • 2
    $\begingroup$ Hawking radiation from a large "supermassive" primordial black hole would be negligible. Supermassive blackholes do produce Hawking radiation (it is supposed) but at extremely low levels. I don't see much of a role for Hawking radiation in nucleosynthesis. $\endgroup$
    – James K
    Jul 3, 2023 at 19:46
  • 2
    $\begingroup$ I was contemplating the accretion disk more than the hawking radiation. The thought was that if the density was sufficient enough in the first place to form a black hole that quickly became macroscopic, then it may also have had sufficient mass and enough surrounding dense gasses to form a metal producing accretion disk. $\endgroup$ Jul 3, 2023 at 20:35
  • $\begingroup$ @JamesK Sorry, I didn't read the supermassive part. Thanks for pointing it out! $\endgroup$
    – Arjun
    Jul 4, 2023 at 17:17
  • $\begingroup$ @NathanStanton Thanks for telling me about that. I will modify my answer $\endgroup$
    – Arjun
    Jul 4, 2023 at 17:18

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