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A black star is a gravitational object composed of matter. It is a theoretical alternative to the black hole concept from general relativity. The theoretical construct was created through the use of semiclassical gravity theory. A similar structure should also exist for the Einstein–Maxwell–Dirac equations system, which is the (super) classical limit of quantum electrodynamics, and for the Einstein–Yang–Mills–Dirac system, which is the (super) classical limit of the standard model.

A black star doesn't need to have an event horizon, and may or may not be a transitional phase between a collapsing star and a singularity. A black star is created when matter compresses at a rate significantly less than the free fall velocity of a hypothetical particle falling to the center of its star, because quantum processes create vacuum polarization, which creates a form of degeneracy pressure, preventing spacetime (and the particles held within it) from occupying the same space at the same time. This vacuum energy is theoretically unlimited, and if built up quickly enough, will stop gravitational collapse from creating a singularity. This may entail an ever-decreasing rate of collapse, leading to an infinite collapse time, or asymptotically approaching a radius bigger than zero.

A black star with a radius slightly greater than the predicted event horizon for an equivalent-mass black hole will appear very dark, because almost all light produced will be drawn back to the star, and any escaping light will be severely gravitationally redshifted. It will appear almost exactly like a black hole. It will feature Hawking radiation, as virtual particle pairs created in its vicinity may still be split, with one particle escaping and the other being trapped. Additionally, it will create thermal Planckian radiation that will closely resemble the expected Hawking radiation of an equivalent black hole.

The predicted interior of a black star will be composed of this strange state of spacetime, with each length in depth heading inward appearing the same as a black star of equivalent mass and radius with the overlayment stripped off. Temperatures increase with depth towards the center.
Sources

Carlos Barceló, Stefano Liberati, Sebastiano Sonego and Matt Visser, Scientific American (October 2009) Black Stars, Not Black Holes
Barceló, C.; Liberati, S.; Sonego, S.; Visser, M. (2008). "Fate of gravitational collapse in semiclassical gravity". Physical Review D. 77 (4): 044032.arXiv:0712.1130. Bibcode:2008PhRvD..77d4032B. doi:10.1103/PhysRevD.77.044032. S2CID 20016596.
Visser, Matt; Barcelo, Carlos; Liberati, Stefano; Sonego, Sebastiano (2009) "Small, dark, and heavy: But is it a black hole?", Bibcode:2009arXiv0902.0346V,arXiv:0902.0346
https://NeutronStarsAndBlackStars.com

See also

Gravastar
Dark-energy star
Black hole
Fuzzball (string theory)

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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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Black holes
Types

Schwarzschild Rotating Charged Virtual Kugelblitz Primordial Planck particle


Size

Micro
Extremal Electron Stellar
Microquasar Intermediate-mass Supermassive
Active galactic nucleus Quasar Blazar

Formation

Stellar evolution Gravitational collapse Neutron star
Related links Tolman–Oppenheimer–Volkoff limit White dwarf
Related links Supernova
Related links Hypernova Gamma-ray burst Binary black hole

Properties

Gravitational singularity
Ring singularity Theorems Event horizon Photon sphere Innermost stable circular orbit Ergosphere
Penrose process Blandford–Znajek process Accretion disk Hawking radiation Gravitational lens Bondi accretion M–sigma relation Quasi-periodic oscillation Thermodynamics
Immirzi parameter Schwarzschild radius Spaghettification

Issues

Black hole complementarity Information paradox Cosmic censorship ER=EPR Final parsec problem Firewall (physics) Holographic principle No-hair theorem

Metrics

Schwarzschild (Derivation) Kerr Reissner–Nordström Kerr–Newman Hayward

Alternatives

Nonsingular black hole models Black star Dark star Dark-energy star Gravastar Magnetospheric eternally collapsing object Planck star Q star Fuzzball

Analogs

Optical black hole Sonic black hole

Lists

Black holes Most massive Nearest Quasars Microquasars

Related

Black Hole Initiative Black hole starship Compact star Exotic star
Quark star Preon star Gamma-ray burst progenitors Gravity well Hypercompact stellar system Membrane paradigm Naked singularity Quasi-star Rossi X-ray Timing Explorer Timeline of black hole physics White hole Wormhole

Physics Encyclopedia

World

Index

Hellenica World - Scientific Library

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