Gravastern

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A Gravastern or Quasi Black Hole Object (QBHO) is a hypothetical celestial object . The origin of the English name "Gravastar" means GRAvitational VAcuum STAR .

According to a hypothesis published in 2001 by Pawel Mazur and Emil Mottola , a very massive star should not develop into a black hole , but would instead become a gravaster. When a (stellar) black hole is formed , the star collapses under its own mass and forms a point-like singularity without spatial expansion. In contrast, in the Gravastern theory it is assumed that the star only collapses up to a certain limit. According to the theory, quantum effects are supposed to cause a kind of phase transition in space-time , which prevents further shrinking of the star.

Mazur and Mottola have suggested that gravastar theory provides a solution to the information paradox of black holes and that gravastars could be sources of gamma-ray bursts. However, many astrophysicists agree that less speculative theories can also be used to explain these phenomena (see the premise “ Occam's razor ”).

From the outside, a Gravastern appears similar to a black hole - both can only be discovered through high-energy radiation, which is created by incident matter. Astronomers searching the sky for radiation signatures to find black holes could not use the measurements to differentiate between black holes and gravastars.

Inside the Gravastern, a bubble of dark energy creates the counter-pressure necessary for stability. The supermassive wall of this bubble is the source of the gravitation of the gravastar.

A whole Gravastern universe was even mentioned in this theory . This would also have an explanation for the dark energy. However, this universe would have to rotate or contain small eddies in spacetime.

There is little interest in the Gravastern theory in general because it is based on a very speculative form of quantum gravity and has no real advantage over black hole theory. Furthermore, from the perspective of quantum gravity, there is no good justification that space should behave in the way Mazur and Mottola assume.

Recent theoretical studies also report that the simultaneous existence of gravastars does not exclude black holes. Gravasterne would therefore no longer make sufficient sense as an alternative model.

A special case of the Gravastern, which differs from the black hole in that the mass is not concentrated in the middle, but in a shell, is the shell collapsar .

literature

  • Pawel O. Mazur; Emil Mottola: Gravitational Condensate Stars: An Alternative to Black Holes , 2001, arxiv : gr-qc / 0109035

Individual evidence

  1. ^ P. Rocha et al .: Bounded excursion stable gravastars and black holes . In: Journal of Cosmology and Astroparticle Physics , 2008, arxiv : 0803.4200

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