If gravitational condensate stars (or gravastars) actually existed, they’d look much like black holes to a distant observer. Two theoretical physicists at Goethe University Frankfurt have now found a brand new solution to Albert Einstein’s theory of general relativity, based on which gravitational stars might be structured like a Russian matryoshka doll, with one gravastar situated inside one other.
The inside of black holes stays a conundrum for science. In 1916, German physicist Karl Schwarzschild outlined an answer to Albert Einstein’s equations of general relativity, based on which the middle of a black hole consists of a so-called singularity, a degree at which space and time now not exist. Here, the idea goes, all physical laws, including Einstein’s general theory of relativity, now not apply; the principle of causality is suspended. This constitutes an important nuisance for science: in spite of everything, it implies that no information can escape from a black hole beyond the so-called event horizon.
This might be a reason why Schwarzschild’s solution didn’t attract much attention outside the theoretical realm for a very long time — that’s, until the primary candidate for a black hole was discovered in 1971, followed by the invention of the black hole in the middle of our Milky Way within the 2000s, and eventually the primary image of a black hole, captured by the Event Horizon Telescope Collaboration in 2019.
In 2001, Pawel Mazur and Emil Mottola proposed a distinct solution to Einstein’s field equations that led to things which they called gravitational condensate stars, or gravastars. Contrary to black holes, gravastars have several benefits from a theoretical astrophysics perspective. On the one hand, they’re almost as compact as black holes and likewise exhibit a gravity at their surface that is actually as strong as that of a black hole, hence resembling a black hole for all practical purposes. However, gravastars don’t have an event horizon, that’s, a boundary from inside which no information could be sent out, and their core doesn’t contain a singularity. As a substitute, the middle of gravastars is made up of an exotic — dark — energy that exerts a negative pressure to the big gravitational force compressing the star. The surface of gravastars is represented by a wafer-thin skin of extraordinary matter, the thickness of which approaches zero.
Theoretical physicists Daniel Jampolski and Prof. Luciano Rezzolla of Goethe University Frankfurt have now presented an answer to the sphere equations of general relativity that describes the existence of a gravastar inside one other gravastar. They’ve given this hypothetical celestial object the name “nestar” (from the English “nested”).
Daniel Jampolski, who discovered the answer as a part of his Bachelor’s thesis supervised by Luciano Rezzolla, says: “The nestar is sort of a matryoshka doll,” adding that, “our solution to the sphere equations allows for an entire series of nested gravastars.” Whereas Mazur and Mottola posit that the gravastar has a near infinite thin skin consisting of normal matter, the nestar’s matter-composed shell is somewhat thicker: “It’s a bit of easier to assume that something like this might exist.”
Luciano Rezzolla, Professor of Theoretical Astrophysics at Goethe University, explains: “It’s great that even 100 years after Schwarzschild presented his first solution to Einstein’s field equations from the overall theory of relativity, it’s still possible to seek out recent solutions. It is a bit like finding a gold coin along a path that has been explored by many others before. Unfortunately, we still do not know how such a gravastar might be created. But even when nestars don’t exist, exploring the mathematical properties of those solutions ultimately helps us to higher understand black holes.”
