by Alex Ammons (6th)
What are gravastars? Gravastars were proposed in 2006 by scientists Pawel Mazur and Emil Mottola as an alternative to the black hole theory. Now before you tell me that there is proof of black holes, I know. But the difference between gravastars and black holes is many. First, gravastars do not have an accretion disc, while black holes do. Second, Gravastars may have the same metric outside as a black hole, but have a de Sitter metric inside.
This theoretical body does not have a singularity, but rather super-condensed nothing. Don’t think about touching it though. Even though gravastars don’t have an accretion disc or singularity, they will rip you apart before you even get close. Gravastars will rip you apart, atom by atom, and when you finally touch the surface, your atoms will be broken down so far they won’t even exist anymore.
Structure
According to Mazur and Mottola, a gravastar is composed of three regions, differentiated by the relationship between pressure p and energy density ρ. The first, inner region is full of false vacuum, or dark energy, and in this region, p=-ρ.
(A theoretical picture of a gravastar)
Surrounding the gravastar is a thin layer of perfect fluid. On the outside is a true vacuum, where the relationship between the density and the energy density is 0. The dark energy-like behavior prevents the star from collapsing into a singularity, and the presence of the thin shell prevents an event horizon from forming, avoiding the infinite blue shift. The inner region has thermodynamically no entropy, and may be a Bose-Einstein condensate. Severe red-shifting of the photons also makes the shell very cold, almost absolute zero.
Nesting Gravastars
Even though gravastars have proven to be the solution to multiple questions about general relativity, researchers have developed a redefined model of a gravastar, allowing two to be nested into each other. This opened up multiple new possibilities in astrophysics and raised some questions. The nesting of gravastars leads to a much thicker shell, compared to the regular thin-shelled gravastar.