When it comes to what remains undiscovered in the universe, astrophysicists may quote Donald Rumsfeld that the universe is full of known unknowns. In addition to the ordinary matter and energy that we are familiar with, the universe is made up of two major mysteries: dark energy and dark matter. Theoretical astrophysicists mathematically construct possible celestial bodies to answer these gaps in our understanding of the unknown. So, in a study published in the journal Classical and Quantum Gravity, a group of astrophysicists proposed a peculiar object called a "nested star" as a solution to the blind spot of Einstein's general theory of relativity.
Nested stars are similar to gravitational vacuum condensing stars, or gravitational stars for short, which are theoretical objects proposed in the early 2000s that have an extremely thin outer layer of matter and a core made of dark energy.
Similar to gravitational stars, nested stars are an extreme theoretical object, but with a difference. In their work, researchers Daniel Jampolski and Luciano Rezzolla proposed that gravitational stars could be nested – hence the name "nested stars" – and "can be extended to as many shells as they want", which they wrote produced a celestial body that offered "a new solution to Einstein's equations."
A nested star is like a nesting doll," Jampolski said in a release at the Goethe University in Frankfurt. "Our solution to the field equation allows for the existence of an entire series of nested gravitational stars. ”
Albert Einstein came up with his equation a century ago; In the decades that followed, other researchers proved them right through their findings. In 1916, he discovered the existence of black holes, and in 1971, he identified them for the first time. But at the center of the black hole, the theory of general relativity collapsed. At the cores of these celestial bodies, time slows to a halt because the gravitational pull is so strong that even light cannot escape, and space compresses to a point of infinite density.
Gravitational stars are proposed to be almost as compact as black holes, with similar gravitational pull on the surface. However, gravitational stars do not have an event horizon – meaning that outside observers can receive information from them – and they do not have a singularity at their core. Instead, their (theoretical) core is made up of dark energy that counteracts the enormous gravitational pull that pulls matter toward the core.
In the Einstein field equations of general relativity, the exact solution has been found before; In fact, the first solution was found by Carl Schwarzschild in the same year that Einstein introduced the theory. Nested stars provide a new solution to the old problem ......If they exist, of course.
The good news is that even 100 years after Schwartzschild proposed his first solution to the Einstein field equations of general relativity, we are still able to find new solutions," Rezzolla said in the same release. "It's a bit like finding a gold coin on a path that many people have explored. ”
Unfortunately, we still don't know how such gravitational stars form," Rezzolla added. "But even if nested stars don't exist, exploring the mathematical properties of these solutions ultimately helps us better understand black holes. ”