Draft:Supermassive star

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A supermassive star (SMS) is a

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]

Description

Although the term "ultramassive star" ("UMS") is rarely used, it has been once used to refer stars between 1,000 and 10,000 M☉.[4]

Formation and properties

The environmental physical conditions to form a supermassive star are the following:

  1. Metal-free gas cloud (gas containing only hydrogen and helium).
  2. Atomic-cooling gas.
  3. Sufficiently large flux of Lyman–Werner photons, in order to destroy hydrogen molecules, which are very efficient gas coolants.

Depending on models, several studies had predicted that supermassive stars could have evolved "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.[5] Researchs predicted that metal-rich supermassive stars may have been able to form from merging of metal-rich protogalaxies.[6][7]

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☉.[8][9]

End of stellar life

Direct collapse

A 2018 study proposed a new model for the direct collapse route.[10]

A scenario whereas a DCBH is formed without stellar phase is called "dark collapse".[11]

Alternative scenarios for the fate for a supermassive star have been proposed by various other researches, although this depends directly on the star's properties.

Quasi-star phase

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 enough weak and will likely encounter the dynamical bar mode instability, which may trigger the growth of nonaxisymmetric bars.[12]

Difference from supermassive nuclear-powered star and dark stars

See also

  • Accretion (astrophysics) – Accumulation of particles into a massive object by gravitationally attracting more matter
  • Accretion disk – Structure formed by diffuse material in orbital motion around a massive central body
  • Quasi-star – Hypothetical early-universe star with a black hole core
  • Dark star (dark matter) – Hypothetical astronomical object heated by dark-matter annihilation

References

  1. S2CID 199452725
    .
  2. doi:10.1036/1097-8542.669400
    .
  3. doi:10.1093/mnras/staa763
    .
  4. doi:10.1146/annurev.astro.44.051905.092549
    .
  5. doi:10.1093/mnras/stx2919
    .
  6. doi:10.1093/mnras/stad572
    .
  7. S2CID 235247984
    .
  8. PMID 35794378
    . State-of-the-art computer simulations show that the first supermassive black holes were born in rare, turbulent reservoirs of gas in the primordial Universe without the need for finely tuned, exotic environments — contrary to what has been thought for almost two decades.
  9. ^ "Scientists discover how first quasars in universe formed". phys.org. Provided by University of Portsmouth. 6 July 2022. Retrieved 2 August 2022.
  10. S2CID 51865966
    .
  11. PMID 30057369
    .
  12. doi:10.1086/318662
    .

Further reading

External links

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