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On the topic of early black hole growth I saw this released a couple of months ago, an early black hole apparently growing at 40x the Eddington limit 1.5 billio

On the topic of early black hole growth I saw this released a couple of months ago, an early black hole apparently growing at 40x the Eddington limit 1.5 billion years after the big bang. https://chandra.si.edu/press/24_releases/press_110424.html https://chandra.si.edu/press/24_releases/press_110424.html > A super-Eddington-accreting black hole ~1.5 Gyr after the Big Bang observed with JWST https://www.nature.com/articles/s41550-024-02402-9 https://www.nature.com/articles/s41550-024-02402-9

dotancohen 2y ago
Correct me if I'm wrong, but the term Eddington limit is a bit misleading as it does not describe some physical rate that cannot be exceeded. Lots of super Eddington objects are known.
- PaulHoule 2y ago
  It's the point where light pressure can blow off the outer layers of a star https://en.wikipedia.org/wiki/Eddington_luminosity https://en.wikipedia.org/wiki/Eddington_luminosity Objects that pulse like https://en.wikipedia.org/wiki/Eta_Carinae https://en.wikipedia.org/wiki/Eta_Carinae can evade it and there are other ways too. When it comes to super-massive black holes there is the question of how quickly stuff can even get close enough to the black hole to get into the accretion disk. 500M years is a long time for the kind of large star that becomes a black hole (blows up in 10M years or so), but if one black hole is going to merge with another black hole and that is going to merge with another black hole and so on there is no Eddington limit (no EM radiation!) but rather the even slower process of shedding angular momentum via gravitational radiation. (One highlight of grad school was the colloquium talk where we got to hear the signal from two black holes colliding almost 20 years before it was detected for real) I hope JWST sees https://en.wikipedia.org/wiki/Stellar_population#Population_III_stars https://en.wikipedia.org/wiki/Stellar_population#Population_... Note those Pop 3 stars have a higher Eddington limit because they've got hardly any "metal" in them which means light interacts with them differently, although astronomers have the strange (to me) conventional that anything heavier than Helium is a metal which includes, say, oxygen. (As a cond-mat PhD I think a metal is something that has free electrons, which could be one of those elements towards the left side of the periodic table or could be a doped semiconductor or polymer like polyaniline)
  - dotancohen 2y ago
    Thank you. I did not know that the first cosmic generation of stars had a higher Eddington limit. Why does light interact differently with hydrogen and helium than it does with the other elements? Does it have anything to do with having only a single layer of electrons in the atom?
- deleted 2y ago
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dotancohen 2y ago

Correct me if I'm wrong, but the term Eddington limit is a bit misleading as it does not describe some physical rate that cannot be exceeded. Lots of super Eddington objects are known.

PaulHoule 2y ago
It's the point where light pressure can blow off the outer layers of a star https://en.wikipedia.org/wiki/Eddington_luminosity https://en.wikipedia.org/wiki/Eddington_luminosity Objects that pulse like https://en.wikipedia.org/wiki/Eta_Carinae https://en.wikipedia.org/wiki/Eta_Carinae can evade it and there are other ways too. When it comes to super-massive black holes there is the question of how quickly stuff can even get close enough to the black hole to get into the accretion disk. 500M years is a long time for the kind of large star that becomes a black hole (blows up in 10M years or so), but if one black hole is going to merge with another black hole and that is going to merge with another black hole and so on there is no Eddington limit (no EM radiation!) but rather the even slower process of shedding angular momentum via gravitational radiation. (One highlight of grad school was the colloquium talk where we got to hear the signal from two black holes colliding almost 20 years before it was detected for real) I hope JWST sees https://en.wikipedia.org/wiki/Stellar_population#Population_III_stars https://en.wikipedia.org/wiki/Stellar_population#Population_... Note those Pop 3 stars have a higher Eddington limit because they've got hardly any "metal" in them which means light interacts with them differently, although astronomers have the strange (to me) conventional that anything heavier than Helium is a metal which includes, say, oxygen. (As a cond-mat PhD I think a metal is something that has free electrons, which could be one of those elements towards the left side of the periodic table or could be a doped semiconductor or polymer like polyaniline)
- dotancohen 2y ago
  Thank you. I did not know that the first cosmic generation of stars had a higher Eddington limit. Why does light interact differently with hydrogen and helium than it does with the other elements? Does it have anything to do with having only a single layer of electrons in the atom?
deleted 2y ago
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