Testing Gravity with Black Hole Images
Researchers are exploring whether future telescopes could distinguish between different theories of gravity by analyzing images of black holes. While current technology isn’t sensitive enough to detect subtle differences, planned upgrades to the Event Horizon Telescope (EHT) - including a potential space-based component – may offer the necessary precision.
To prepare for this possibility, a team from Shanghai adn CERN revisited an analysis conducted before the original EHT became operational. Instead of testing specific alternative gravity theories, they utilized a flexible model called the Konoplya-Rezzolla-Zhidenko metric. This model allows for adjustments to key parameters, effectively simulating a range of gravitational behaviors without being tied to a single hypothesis.The researchers tested four variations of this metric, comparing the results to the standard predictions of general relativity (the Kerr metric).
Using hydrodynamic simulations, they modeled the surroundings around a black hole, including infalling matter, magnetic fields, and the resulting jets of material. The simulated images closely resembled those produced by the EHT: a bright, asymmetrical ring caused by the black holeS rotation.
Even though the differences between the various gravity models were subtle, they were present. One variation resulted in a smaller, brighter ring, while another showed reduced contrast between the bright and dim sides. Differences were also observed in the width of the simulated jets. These findings suggest that next-generation telescopes could perhaps reveal clues about the true nature of gravity by carefully analyzing the details of black hole environments.
