I've learned that metallicity is a very important factor to consider when talking about a star's formation and lifecycle. That gets me wondering whether a high enough metallicity could prevent the formation of proper stars altogether. Would it happen when the metallicity is so high that the hydrogen concentration isn't high enough to initiate a self-sustaining fusion reaction?

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    $\begingroup$ There is no limit associated with phenomenon you suggest, it just raises the minimum mass for "starhood". $\endgroup$
    – ProfRob
    Aug 30, 2021 at 18:52
  • $\begingroup$ Couldn't it hypothetically be so high that the mass required to initiate fusion would cause the would-be star to simply collapse into a black hole? Not that I'm saying this could ever happen. $\endgroup$
    – zucculent
    Aug 30, 2021 at 20:06
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    $\begingroup$ No. It would rise to around half a solar mass if there were no hydrogen at all at which point the helium would burn. Or about 1 solar mass and the carbon and oxygen would burn. $\endgroup$
    – ProfRob
    Aug 30, 2021 at 20:18
  • $\begingroup$ Sounds like the only way to keep fusion from happening at all would be if a would-be star's chemical makeup was devoid of any elements capable of exothermic fusion reactions. $\endgroup$
    – zucculent
    Aug 30, 2021 at 20:32
  • $\begingroup$ Maybe you'd be interested in the so called "quasi-star" (or black hole star) which is powered by a compact object at their cores en.wikipedia.org/wiki/Quasi-star $\endgroup$ Aug 30, 2021 at 21:35


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