What does current research say about the elements that can be created in the accretion disc of a black hole, and does the Relativistic Jet contain any of those elements?

Curious as to whether the relativistic jet contributes to the dispersion of heavier elements throughout the universe.


1 Answer 1


Black hole jets will expel whatever heavy elements are present in the material that they are accreting. Heavy elements are not created in the accretion discs of black holes.

Even the hottest parts of the hottest accretion discs in the universe (those around "small" black holes and neutron stars) only reach temperatures of $\sim 10^{7}$ K and have densities far below that at the centre of a star. So no nuclear fusion reactions can take place. There is also no source of free neutrons to allow the r- or s-process to take place.

Having said that, there is little doubt that accretion-powered jets are important energy sources in the interstellar medium and these can drive outflows that transport metal-enriched material (not necessarily in the accretion disk of the black hole, but in its local environment) to more distant locations, particularly in galaxy clusters (e.g. Kirkpatrick et al. 2011; Prasad et al. 2018).

The exception to the above statements are the probable accretion disks that form around the products of neutron star/neutron star and neutron star/black hole mergers. These mergers may be responsible for (short) Gamma Ray burst sources and will be surrounded by neutron-rich material from the neutron star(s). Here it seems quite feasible that r-process elements (heavy, neutron-rich elements) will be formed by rapid neutron capture and expelled by the jets for some brief period of time (e.g. Janiuk 2019).

  • $\begingroup$ Thank you, this was a very informative answer, I especially appreciate the links to papers. $\endgroup$
    – Demis
    Mar 17, 2020 at 19:09
  • $\begingroup$ "Belyanin & Derishev (2001) analyzed the possibility of self-sustained neutron halo formation in the vicinity of a disk- accreting black hole. They found that neutrons decouple from protons and pile up in the inner disk, leading to the formation of the halo. Mukhopadhyay & Chakrabarti (2000) showed that sig- nificant nucleosynthesis is possible in the accretion around a 10 or 106 M􏰈 black hole." iopscience.iop.org/article/10.1086/588085/pdf. This article seems to disagree with the answer given. I cannot judge either way, is this article dated? 2008. $\endgroup$
    – JohnHunt
    May 1 at 4:57
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    $\begingroup$ @JohnHunt thanks for this. This is an odd one. These papers and a few others have popped up over the years, especially in the context of multiple populations in globular clusters, but are not widely cited. However, neither do I see papers saying the ideas don't work. Anyway my unequivocal statement is in need of modification. $\endgroup$
    – ProfRob
    May 1 at 5:42
  • $\begingroup$ Thanks. I really appreciate your perspective and expertise on these matters. $\endgroup$
    – JohnHunt
    May 1 at 21:28

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