A quasi-star (also called black hole star) is a hypothetical type of extremely massive and luminous star that may have existed early in the

history of the Universe History (derived ) is the systematic study and the documentation of the human activity. The time period of event before the invention of writing systems is considered prehistory. "History" is an umbrella term comprising past events as well ...

. Unlike modern stars, which are powered by

nuclear fusion Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles ( neutrons or protons). The difference in mass between the reactants and products is manife ...

in their cores, a quasi-star's

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...

would come from material falling into a black hole at its core.

Formation and properties

A quasi-star would result from the core of a large

protostar A protostar is a very young star that is still gathering mass from its parent molecular cloud. The protostellar phase is the earliest one in the process of stellar evolution. For a low-mass star (i.e. that of the Sun or lower), it lasts about 50 ...

collapsing into a black hole, where the outer layers of the protostar are massive enough to absorb the resulting burst of energy without being blown away or falling into the black hole, as occurs with modern supernovae. Such a star would have to be at least . Quasi-stars may have also formed from dark matter halos drawing in enormous amounts of gas via gravity, which can produce supermassive stars with tens of thousands of solar masses. Formation of quasi-stars could only happen early in the development of the Universe, before hydrogen and helium were contaminated by heavier elements; thus, they may have been very massive

Population III During 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926: Baade noticed th ...

stars. Such stars would dwarf

VY Canis Majoris VY Canis Majoris (abbreviated to VY CMa) is an extreme oxygen-rich (O-rich) red hypergiant (RHG) or red supergiant (RSG) and pulsating variable star from the Solar System in the slightly southern constellation of Canis Major. It is o ...

and

Stephenson 2-18 Stephenson 2-18 (abbreviated to St2-18), also known as Stephenson 2 DFK 1 or RSGC2-18, is an enigmatic red supergiant (RSG) or possible extreme red hypergiant (RHG) star in the constellation of Scutum. It lies near the open cluster Ste ...

, both among the largest known modern stars, in size. Once the black hole had formed at the core of the protostar, it would continue generating a large amount of

radiant energy Radiant may refer to: Computers, software, and video games * Radiant (software), a content management system * GtkRadiant, a level editor created by id Software for their games * Radiant AI, a technology developed by Bethesda Softworks for '' ...

from the infall of stellar material. This constant outburst of energy would counteract the force of

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

, creating an equilibrium similar to the one that supports modern fusion-based stars. Quasi-stars would have had a short maximum lifespan, approximately 7 million years, during which the core black hole would have grown to about . These

intermediate-mass black hole An intermediate-mass black hole (IMBH) is a class of black hole with mass in the range 102–105 solar masses: significantly more than stellar black holes but less than the 105–109 solar mass supermassive black holes. Several IMBH candidate obje ...

s have been suggested as the progenitors of modern

supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical ob ...

s. Quasi-stars are predicted to have surface temperatures higher than . At these temperatures, and with radius of approximately , or times that of the Sun, each one would be about as luminous as a small galaxy. As a quasi-star cools over time, its outer envelope would become transparent, until further cooling to a limiting temperature of . This limiting temperature would mark the end of the quasi-star's life, since there is no

hydrostatic equilibrium In fluid mechanics, hydrostatic equilibrium (hydrostatic balance, hydrostasy) is the condition of a fluid or plastic solid at rest, which occurs when external forces, such as gravity, are balanced by a pressure-gradient force. In the planetary ...

at or below this limiting temperature. The object would then quickly dissipate, leaving behind the

intermediate mass black hole An intermediate-mass black hole (IMBH) is a class of black hole with mass in the range 102–105 solar masses: significantly more than stellar black holes but less than the 105–109 solar mass supermassive black holes. Several IMBH candidate obje ...

References

{{Portal bar, Physics, Astronomy, Spaceflight, Outer space, Solar System, Science Black holes Star types Hypothetical stars

Formation and properties

See also

References