Draft:Supermassive star
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A supermassive star (SMS) is a hypothetical type of extremely massive and luminous star with its mass being on the order of more than a thousand times the mass of the Sun (M☉).[1][2] Such stars may have existed early in the universe (i.e., at high redshift) and may have produced high-mass black hole seeds like direct collapse black holes (DCBHs).[3]
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Last edited by ZaperaWiki44 (talk | contribs) 13 days ago. (Update) |
Description
- Proposed subtypes of supermassive stars: There are several proposed terms and subtypes of supermassive stars, per their masses.
Formation and properties
- Formation: The environmental physical conditions to form a supermassive star are the following:
- Atomic-cooling gas.
- Galaxy merger
- Sufficiently large flux of Lyman–Werner photons, in order to destroy hydrogen molecules, which are very efficient gas coolants.
- A computer simulation reported in July 2022 showed that a halo at the rare convergence of strong, cold accretion flows can create massive black holes seeds without the need for ultraviolet backgrounds, supersonic streaming motions, or even atomic cooling. Cold flows produced turbulence in the halo, which suppressed star formation. In the simulation, no stars formed in the halo until it had grown to 40 million solar masses at a redshift of 25.7 when the halo's gravity was finally able to overcome the turbulence; the halo then collapsed and formed two supermassive stars that died as DCBHs of 31,000 and 40,000 M☉.[5][6]
- Evolution as "red supergiant protostars": Depending on models, several studies had predicted that supermassive stars could have evolved into "red supergiant protostars" as high accretion rates would prevent stars to contract, resulting lower temperatures and radii reaching up to many tens of thousands of R☉, comparable to some of the largest known black holes.[7] Such stars would have been significantly larger than the largest modern red supergiant stars (such as VY Canis Majoris and Mu Cephei) found in the Local Group.[8][9]
- Metal-rich: Research predicted that metal-rich supermassive stars may have been able to form from the merging of metal-rich protogalaxies.[10][11]
End of stellar life
Direct collapse
- A 2018 study proposed a new model for the direct collapse route.[13]
- A scenario whereas a DCBH is formed without stellar phase is called "dark collapse".[13]
Various other researchers have proposed alternative scenarios for the fate of a supermassive star, although it may depend directly on the star's properties.
General relativistic supernova
Quasi-star phase
- Short summary:
- After the QS phase per old models and studies:
- Coughlin et al. 2024 model:
- Objections, to be shortened: Models from a 2023 paper, although they did not follow the collapse of supermassive stars to late times, predicted that X-rays from the central black hole is unlikely to halt the collapse of stars with final masses between 3,500 and 370,000 M☉ due to too large infall velocities (that enclose most of the stellar mass), thus instead resulting a direct collapse black hole.[10]
Bar-mode instability
Although thermal emission from a rotating supermassive star will cause the configuration to contract slowly and spin up, the contracting and cooling star may rotate differentially if internal viscosity and magnetic fields are weak enough and will likely encounter the dynamical bar mode instability, which may trigger the growth of nonaxisymmetric bars.[14]
Post-main sequence
- Mass loss until becoming a few-100-solar-masses sub-Eddington star:[12]
Difference from supermassive nuclear-powered stars and dark stars
- Will also mention the dark star formation:
