Black holes are some of the most enigmatic objects in the universe, capable of warping the fabric of space around them so strongly that even light cannot escape their gravitational grip. But it turns out that much of what scientists know about these mysterious objects may be wrong.
According to new research published in April in the journal Physical examination Dblack holes may actually be completely different celestial beings known as gravastars.
“Gravastars are hypothetical astronomical objects that have been introduced [in 2001] as alternatives to black holes,” co-author of the study João Luis Rosa, a physics professor at the University of Gdansk in Poland, told Live Science in an email. “They can be interpreted as stars made of vacuum energy or dark energy: the same type of energy that drives the accelerated expansion of the universe.”
Resolving the Paradoxes of Black Holes with Gravitational Stars
Carl Schwarzschild, a German physicist and astronomer, first predicted black holes in 1915 based on calculations using Albert Einstein general relativity.
Over the years, astronomical observations seem to confirm the existence of objects resembling black holes. However, Schwarzschild’s description of these cosmic bodies has some flaws.
In particular, the center of a black hole is predicted to be a point of infinitely high density, called a singularity, where all of the black hole’s mass is concentrated but fundamental physics teaches us that infinities do not exist and their appearance in any theory signals its inaccuracy or incompleteness.
“These problems indicate that something is wrong or incomplete in the black hole model and that alternative models need to be developed,” Rosa said. “Gravastar is one of many alternative models proposed. The main advantage of gravastars is that they have no features.”
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Like ordinary black holes, gravastars must arise at the final stage of the evolution of massive stars, when the energy released during the thermonuclear burning of matter inside them is no longer sufficient to overcome the force of gravity, and the star collapses in a much denser object. But unlike black holes, grava stars are not expected to have any features and are thought to be thin spheres of matter whose stability is maintained by the dark energy contained within them.
To find out if gravastars are viable alternatives to individual black holes, Rosa and his colleagues studied the interaction of particles and radiation with these hypothetical objects.
Using EinsteinAccording to the authors’ theory, they investigated how the huge masses of hot matter that surround supermassive black holes would appear if these black holes were actually gravastars. They also looked at the properties of “hotspots“—giant bubbles of gas orbiting black holes at near the speed of light.
Their findings revealed striking similarities between the emission of matter from gravastars and black holes, suggesting that gravastars do not contradict scientists’ experimental observations of the universe. The team also discovered that the gravastar itself should look almost like a single black hole, creating a visible shadow.
“This shadow is not caused by light being trapped in the event horizon, but by a slightly different phenomenon called ‘gravitational redshift,’ which causes light to lose energy as it moves through a region of strong gravitational field,” said Rosa . “Indeed, when the light emitted from regions close to these alternative objects reaches[es] our telescopes, most of its energy would be lost to the gravitational field, causing this shadow to appear.”
The striking similarities between the Schwarzschild black hole model and gravamen highlight the latter’s potential as a realistic alternative free from the theoretical trappings of singularities.
However, this theory needs to be supported by experiments and observations, which the authors of the study believe may soon be conducted. While grava stars and individual black holes may behave similarly in many ways, subtle differences in the light they emit could potentially tell them apart.
“To test our results experimentally, we rely on the next generation of observational experiments in gravitational physics,” Rosa said, referring to the hunt for black holes Event Horizon Telescope and on GRAVITY+ instrument is being added to the Very Large Telescope in Chile. “These two experiments aim to take a closer look at what happens near the center of galaxies, specifically our own Milky Way.”
