Study models how collapsing stars could form gravastars
A new theoretical paper proposes that some stellar collapses could produce dense gravastars with expanding miniature universes inside.
By Lucas Ferreira · Science & Environment Writer
3 min read
A massive dying star may have a theoretical escape route from becoming a black hole: forming a gravastar powered by an expanding inner cosmos. The proposal matters because it offers a possible way around the singularities and event horizons that make black holes difficult to reconcile with known physics.
The idea comes from Daniel Jampolski and Luciano Rezzolla of Goethe University Frankfurt, whose paper, “Formation of gravastars,” was published in Physical Review D, according to the university. They describe what Goethe University Frankfurt calls the first dynamic solution to Einstein’s general relativity equations showing how ordinary collapsing matter could form such an object.
What the model proposes
In standard astrophysics, a very massive star shines while nuclear fusion in its core creates outward pressure. When the star exhausts its fuel, Goethe University Frankfurt said, that pressure can no longer hold off gravity, and the star collapses.
The usual theoretical endpoint is a black hole, with matter squeezed toward a singularity and hidden behind an event horizon. Physicists broadly accept black holes, but the university said they still pose unresolved problems because physics cannot reliably describe infinite density or infinitely curved spacetime, and because information beyond an event horizon cannot be observed.
Jampolski and Rezzolla’s model suggests that, late in the collapse, a small universe could form inside the star. Goethe University Frankfurt said this interior universe would expand under the influence of dark energy, producing pressure that pushes outward against gravity.
If that outward pressure balances the inward collapse, the result would be a gravastar, according to the researchers. Such an object would be extremely compact and massive, resembling a black hole from the outside because of its strong gravity, but it would not contain a singularity or an event horizon.
Why gravastars are of interest
Gravastars have been discussed for about 25 years as possible alternatives to black holes, according to Goethe University Frankfurt. In the proposed structure, ordinary matter would form the exterior layers, while dark energy would fill the interior and resist total collapse.
The new work addresses a long-standing weakness in that concept: how a gravastar could arise from the collapse of real stellar material. Goethe University Frankfurt said Jampolski developed the solution during his master’s thesis under Rezzolla’s supervision.
Jampolski said, according to the university, that the interior “Big Bang” could occur only after the star had nearly reached the point of black-hole formation. He also said matter compressed to extreme density may produce effects that are not yet understood.
Rezzolla, a professor of theoretical astrophysics at Goethe University Frankfurt, cautioned that studying gravastars does not amount to dismissing black holes. The university said he described black holes as the most natural and simplest outcome of gravitational collapse, while arguing that theoretical physics should also test more exotic possibilities.
The work remains theoretical. Goethe University Frankfurt presented it as a model for how gravastars could form, not as evidence that any known object already identified as a black hole is actually a gravastar.
This story draws on original reporting from ScienceDaily.