“For many years there was a theory that light orbits black holes and creates echoes.”
Astrophysicists have developed innovative technique for searching for light echoes from black holeswhich works regardless of how scientists have examined these parameters in the past.
A new method that will make it easier to measure the mass and rotation of black holeswas published in The Astrophysical Journal Letters and may provide direct evidence that photons orbit black holes through an effect known as “gravitational lensing.”
The gravitational lensing effect occurs when Light passes near a black hole and its path is deflected by a strong gravitational field. black hole. This effect allows light to take multiple paths from a source to an observer on Earth: some light rays may follow a direct path, while others may circle the black hole one or more times before reaching us. This means that light from the same source can arrive at different times, resulting in an “echo”.
“For many years it was assumed that light orbits black holes and creates echoes, but these echoes have not yet been measured,” the study’s lead author said in a statement. George N. Wong, scientist at the Institute for Advanced Study and fellow at the Princeton Gravity Initiative at Princeton University. “Our method provides a model for making these measurements that has the potential to revolutionize our understanding of black hole physics.”
This technique isolates weak echoes from the more intense direct light collected by established interferometric telescopes such as the Event Horizon Telescope. Both Wong and one of her co-authors, Leah Medeiros, a NASA Einstein Fellow at Princeton University, have been active in the Event Horizon Telescope Collaboration.
To test their technique, Wong and Medeiros collaborated with James Stone, a professor in the School of Natural Sciences, and Alejandro Cardenas-Avendaño, a Feynman Fellow at Los Alamos National Laboratory and a former postdoctoral fellow at Princeton University, to conduct high-resolution simulations. What took tens of thousands of “snapshots” of light traveling around a black hole supermassive, similar to the one found at the center of the M87 galaxy (star M87), which is located approximately 55 million light years from Earth.
Using these simulations, the team demonstrated that their method could directly determine the echo latency period in simulated data. They believe that their method will be applicable to other black holes besides the star M87.
“This method will not only confirm when the light orbiting a black hole was measured, but also will provide a new tool to measure the fundamental properties of a black hole” explains Medeiros.
Understanding these properties is important. “Black holes play an important role in shaping the evolution of the universe,” says Wong. “While we often focus on how black holes attract objects, they also release large amounts of energy into their surroundings.
“They play an important role in the development of galaxies.influencing how, when and where stars form, and helping to determine how the structure of the galaxy itself evolves. “Knowing the distribution of black hole masses and spins, and how these distributions change over time, greatly improves our understanding of the universe.”
Measuring the mass or spin of a black hole is difficult. The nature of the accretion disk, that is, the rotating structure of hot gas and other matter that spirals into the black hole, which can confuse measurementssays Wong. However, the light echo provides an independent measurement of mass and rotation, and having multiple measurements allows us to get an estimate of those parameters “that we can actually believe in,” Medeiros says.
Detecting the light echo could also allow scientists to better test Albert Einstein’s theories of gravity. “Using this technique, we can find things that make us think, ‘Hey, this is weird!'” Medeiros adds. “Analyzing this data can help us test whether black holes actually conform to general relativity.”
The team’s results show that it may be possible to detect the echo using a couple of telescopesone on Earth and one in space, work together to perform what can be called “very long-baseline interferometry,” Wong says. Such an interferometry mission would have to be “modest,” he said. Their technique provides a manageable and practical method for collecting important and reliable information about black holes.
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