Once thought to be enigmatic objects with infinitely dense centers and inescapable gravitational pull, black holes may have a different explanation: gravastars.
Gravastars, introduced in 2001, are hypothetical celestial entities made of vacuum energy or dark energy, the same type propelling the accelerated expansion of the universe. Unlike black holes with their predicted singularities, gravastars are theorized to be thin spheres of matter stabilized by dark energy within them.
Researchers, including Pawel O. Mazur from the University of Gdańsk in Poland, have examined the interaction of particles and radiation with gravastars. Their findings, published in the journal Classical and Quantum Gravity, reveal striking similarities between the matter emissions of gravastars and black holes, suggesting that gravastars don’t contradict scientists’ experimental observations of the universe.
Moreover, the team discovered that a gravastar itself should appear almost like a singular black hole, creating a visible shadow. However, this shadow in gravastars is caused by gravitational redshift, where light loses energy in strong gravitational fields, rather than the trapping of light in an event horizon as in black holes.
The striking resemblances between Schwarzschild’s black hole model and gravastars highlight the latter’s potential as a realistic alternative, free from the theoretical pitfalls of singularities. While gravastars and singular black holes might behave similarly in many respects, subtle differences in emitted light could potentially distinguish them.
To test their theory experimentally, researchers are counting on the next generation of observational experiments in gravitational physics, such as the Event Horizon Telescope (EHT) and the Multi-Object Spectrograph Instrument (MOSI) being added to the Very Large Telescope in Chile. These experiments aim to observe closely what happens near the center of galaxies, including our own, and may help shed light on the true nature of these enigmatic objects.
