There are hardly any limits to the imagination of physicists. About twenty years ago she brought the fascinating concept of Gravastar to life. Today she is once again pushing the boundaries of reality by proposing the idea of nestars, nested stars. Like so many Russian dolls!
It's a pretty fascinating theory. As a kind of alternative to describing black holes. It was proposed in 2001 by two American physicists Emil Mottola and Pawel Mazur. This is the so-called gravastar theory, a portmanteau for “gravitational vacuum star.” And before we go any further, it's interesting to point out that it's far from unanimous in the scientific community.
Nevertheless, let’s take a look at how the two physicists imagine their “gravitational vacuum stars”. Well, like an object that is almost as compact as a black hole and has just as much surface gravity. But like an object that has neither an event horizon, i.e. a boundary within which no information can be sent, nor a core singularity.
The Gravaster as an alternative to the black hole
This requires clarification. It was the German physicist Karl Schwarzschild who proposed a solution to Albert Einstein's equations, according to which the center of a black hole would consist of a singularity. You see, from a point where space and time no longer exist. Where the laws of physics no longer apply. This means that no information could escape from a black hole beyond the so-called event horizon.
The Gravastars from Mottola and Mazur are a little different. Its core would be composed of exotic energy that would exert negative pressure on the colossal gravitational force compressing the star. Their surface would amount to a solid, solid skin made of more ordinary material. Solid but thin, as researchers estimate its thickness to be almost zero.
Gravastars nested like Russian dolls
More than 20 years after the first mention of grava stars, physicists from Goethe University (Germany), Daniel Jampolski and Luciano Rezzolla, are still proposing an alternative. A completely speculative alternative, which they present in the very serious specialist magazine Classical Quantum Gravity. And her solution turns out to be crazier than that of her colleagues. It describes the existence of grava stars within other grava stars. Like Russian dolls, the famous matryoshkas. Researchers have even come up with a name for these incredible objects. They call them “nestars,” a word derived from the English word “nested,” meaning “nested.” And in their opinion, their shell would be easier to imagine since it is slightly thicker than that of the gravaster.
“It is great that 100 years after Schwarzschild presented his first solution to Einstein's equations from general relativity, it is still possible to find new solutions. It's a bit like finding a gold coin on a path that many others have explored. Unfortunately, we still don't know how such a gravaster came to be. But even if nestars do not exist, exploring the mathematical properties of these solutions ultimately helps us to better understand black holes,” explains Luciano Rezzolla, Professor of Astrophysics and Theoretical Astrophysics, in a press release from Goethe University about his enthusiasm.