[ad_1]
Black holes are known to be compact objects where the paths of light are greatly curved by the curvature of space-time. While light itself cannot escape from the central mass on the event horizon, at farther distances, light can orbit the black hole. This phenomenon can allow a distant observer to see several versions of the same object. Although this has been known for years, it is only now that theoretical physicists have an exact mathematical solution.
From any location outside of a black hole’s event horizon, there are an infinite number of paths for light to an observer; each of these paths differs in the number of orbits turned around the black hole and in their proximity to the last orbit of the photon. Image credit: Sci-News.com / Zdeněk Bardon / ESO.
“A distant galaxy is shining in all directions – some of its light is approaching the black hole and is slightly deflected; some of the light comes even closer and goes around the hole just once before escaping to us, and so on, ”said Albert Sneppen, a student at the Cosmic Dawn Center and the Niels Bohr Institute from the University of Copenhagen.
“Looking near the black hole, we see more and more versions of the same galaxy, the closer we get to the edge of the hole.”
“How far from the black hole do you have to look from one image to see the next image?” The result has been known for over four decades and is approximately 500 times. “
“Calculating this is so complicated that until recently we had not yet developed a mathematical and physical intuition as to why it is this exact factor.”
With a simple numerical solution and a disrupted analytical solution, Sneppen has succeeded in proving why.
“There is something fantastically beautiful about understanding now why the images repeat themselves in such an elegant way,” he said.
“On top of that, it offers new opportunities to test our understanding of gravity and black holes.”
Light from the background galaxy circles a black hole an increasing number of times the closer it passes, and an observer therefore sees the same galaxy in more than one direction. Image credit: Peter Laursen.
The new method can also be generalized to black hole spinning.
“It turns out that when the black hole is spinning really fast, you don’t need to come close to a factor of 500 anymore, but a lot less,” Sneppen said.
“In fact, each frame is now only 50, or 5, or even up to twice as close to the edge of the black hole.”
Having to look 500 times closer to the black hole for each new image means the images are quickly “compressed” into a single image.
“In practice, the many images will be difficult to observe,” he said.
“But when black holes rotate, there is more room for additional images, so we can hope to confirm the theory by observation in the not-so-distant future.”
“This way we can learn more about black holes, but also about the galaxies behind them. “
“The travel time of light increases, the more it has to go around the black hole, so the images are more and more delayed.”
“If, for example, a star exploded as a supernova in a galaxy in the background, we could see that explosion over and over again. “
The study was published in the journal Scientific reports.
_____
A. Sneppen. 2021. Divergent reflections around the photonic sphere of a black hole. Scientific representative 11, 14247; doi: 10.1038 / s41598-021-93595-w
[ad_2]
Source link