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A quasi-star (also called black hole star) is a hypothetical type of extremely massive and luminous star that may have existed very early in the history of the Universe. Unlike modern stars, which are powered by nuclear fusion in their hot cores, a quasi-star's energy would come from material falling into a black hole at its core.[1]
Size comparison of a quasi-star compared to several known super & hypergiant stars, including also the largest known stars.

A quasi-star is predicted to have formed when the core of a large protostar collapses into a black hole during its formation and the outer layers of the star are massive enough to absorb the resulting burst of energy without being blown away (as they are with modern supernovae) - or falling into the supermassive blackhole. Such a star would have to be at least 1,000 solar masses (2.0×1033 kg).[1] These stars may have also been formed by dark matter halos drawing in enormous amounts of gas via gravity, in the early universe, which can produce supermassive stars with tens of thousands of solar masses.[2][3] Stars this large could only form early in the history of the Universe before the hydrogen and helium were contaminated by heavier elements; thus, they may have been very massive Population III stars. It is even larger than VY Canis Majoris and Stephenson 2-18, which are both among the largest known stars and red supergiants.

Once the black hole had formed at the core of the protostar, it would continue generating a large amount of radiant energy from the infall of additional stellar material. This energy would counteract the force of the gravity, creating an equilibrium similar to the one that supports modern fusion-based stars.[4] A quasi-star is predicted to have had a maximum lifespan of about 7 million years,[5] during which the core black hole would have grown to about 1,000–10,000 solar masses (2×1033–2×1034 kg).[1][4] These intermediate-mass black holes have been suggested as the origin of the modern era's supermassive black holes. Quasi-stars are predicted to have surface temperatures higher than 10,000 K (9,700 °C) and to cool over time.[4] At these temperatures, and with diameters of approximately 10 billion kilometres (66.85 au) or 7,187 times that of the Sun, each one would produce as much light as a small galaxy.[1] Once they cool to 10000 K, the outer envelope of the quasi-star becomes transparent, cooling rapidly to a limiting temperature of 4,000 K (3,730 °C). This limiting temperature marks the end of the quasi-star's life; there is no hydrostatic equilibrium at or below this limiting temperature, so the object quickly dissipates, leaving behind an intermediate mass black hole.[4]
See also

Astronomy portal iconStar portal

Quasar
Thorne–Żytkow object
Hypergiant
Supergiant

References

Battersby, Stephen (29 November 2007). "Biggest black holes may grow inside 'quasistars'". NewScientist.com news service.
Yasemin Saplakoglu (29 September 2017). "Zeroing In on How Supermassive Black Holes Formed" . Scientific American. Retrieved 8 April 2019.
Mara Johnson-Goh (20 November 2017). "Cooking up supermassive black holes in the early universe". Astronomy. Retrieved 8 April 2019.
Begelman, Mitch; Rossi, Elena; Armitage, Philip (2008). "Quasi-stars: accreting black holes inside massive envelopes". MNRAS. 387 (4): 1649–1659. arXiv:0711.4078. Bibcode:2008MNRAS.387.1649B. doi:10.1111/j.1365-2966.2008.13344.x. S2CID 12044015.

Schleicher, Dominik R. G.; Palla, Francesco; Ferrara, Andrea; Galli, Daniele; Latif, Muhammad (25 May 2013). "Massive black hole factories: Supermassive and quasi-star formation in primordial halos". Astronomy and Astrophysics. 558: A59. arXiv:1305.5923. Bibcode:2013A&A...558A..59S. doi:10.1051/0004-6361/201321949. S2CID 119197147.

vte

Stars
Formation

Accretion Molecular cloud Bok globule Young stellar object
Protostar Pre-main-sequence Herbig Ae/Be T Tauri FU Orionis Herbig–Haro object Hayashi track Henyey track

Evolution

Main sequence Red-giant branch Horizontal branch
Red clump Asymptotic giant branch
super-AGB Blue loop Protoplanetary nebula Planetary nebula PG1159 Dredge-up OH/IR Instability strip Luminous blue variable Blue straggler Stellar population Supernova Superluminous supernova / Hypernova

Spectral classification

Early Late Main sequence
O B A F G K M Brown dwarf WR OB Subdwarf
O B Subgiant Giant
Blue Red Yellow Bright giant Supergiant
Blue Red Yellow Hypergiant
Yellow Carbon
S CN CH White dwarf Chemically peculiar
Am Ap/Bp HgMn Helium-weak Barium Extreme helium Lambda Boötis Lead Technetium Be
Shell B[e]

Remnants

White dwarf
Helium planet Black dwarf Neutron
Radio-quiet Pulsar
Binary X-ray Magnetar Stellar black hole X-ray binary
Burster

Hypothetical

Blue dwarf Green Black dwarf Exotic
Boson Electroweak Strange Preon Planck Dark Dark-energy Quark Q Black Gravastar Frozen Quasi-star Thorne–Żytkow object Iron Blitzar

Stellar nucleosynthesis

Deuterium burning Lithium burning Proton–proton chain CNO cycle Helium flash Triple-alpha process Alpha process Carbon burning Neon burning Oxygen burning Silicon burning S-process R-process Fusor Nova
Symbiotic Remnant Luminous red nova

Structure

Core Convection zone
Microturbulence Oscillations Radiation zone Atmosphere
Photosphere Starspot Chromosphere Stellar corona Stellar wind
Bubble Bipolar outflow Accretion disk Asteroseismology
Helioseismology Eddington luminosity Kelvin–Helmholtz mechanism

Properties

Designation Dynamics Effective temperature Luminosity Kinematics Magnetic field Absolute magnitude Mass Metallicity Rotation Starlight Variable Photometric system Color index Hertzsprung–Russell diagram Color–color diagram

Star systems

Binary
Contact Common envelope Eclipsing Symbiotic Multiple Cluster
Open Globular Super Planetary system

Earth-centric
observations

Sun
Solar System Sunlight Pole star Circumpolar Constellation Asterism Magnitude
Apparent Extinction Photographic Radial velocity Proper motion Parallax Photometric-standard

Lists

Proper names
Arabic Chinese Extremes Most massive Highest temperature Lowest temperature Largest volume Smallest volume Brightest
Historical Most luminous Nearest
Nearest bright With exoplanets Brown dwarfs White dwarfs Milky Way novae Supernovae
Candidates Remnants Planetary nebulae Timeline of stellar astronomy

Related articles

Substellar object
Brown dwarf Sub-brown dwarf Planet Galactic year Galaxy Guest Gravity Intergalactic Planet-hosting stars Tidal disruption event

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