Black holes have been that elusive, mystifying entity lurking deep in space, fascinating our every waking thought. The scientists would go on speculating about its existence for decades, but it wasn’t until 2019 that we got a glimpse of a real picture. The real stunner, though, is how this first computer visualization of a black hole, done 40 years ago, surprisingly came quite close to the actual photo taken with instruments of the Event Horizon Telescope.
It wasn’t until 1979 that a French cosmologist named Jean-Pierre Luminet took up the visualization of a black hole. Black holes were hardly observable those days. Yet, even within this obscure observation, Luminet felt he had to simulate what a black hole would look like using Einstein’s theory of general relativity. He used a computer to plot hundreds of thousands of black dots on a white sheet, and then developed a photographic negative to give him his final image. His simulation showed a dark circle circled by a glowing ring of light an image shockingly close to the real thing seen in 2019.
As if the universe were acting according to some script written by the laws of physics. One side of the light ring encircling the black center of the Luminet black hole seemed brighter than the other. That said, gases orbiting a black hole are always moving at incredible velocities and hence constantly produce Doppler beaming. The near side is actually brighter than the far side because of the differential gravitational potential around the black hole. According to his theory, Einstein postulated that light became distorted due to the gravitational pull of the black hole.
Fast forward to April 2017, when a network of telescopes around the world teamed up to act as one—the Event Horizon Telescope. Stretched around the globe from the South Pole to Hawaii and Europe, the “virtual” telescope aimed to capture an image of the supermassive black hole residing at the center of the galaxy M87. It took eight radio observatories chained together to make up an Earth-sized telescope monumentally.
It took the team two years of number-crunching and data analysis to come up with the historic image, says Harvard Astronomer Shep Doeleman, who led the team. He said it was seeing what was deemed to be unseeable. He explained that a glowing, orange-colored ring empowers the event horizon of the black hole. That is, he added, the point beyond which nothing, not even light, can flee from the gravitational pull of the black hole.
Remarkable is the degree to which so many of those features that popped up in Luminet’s simulation made it into this first real image: the glowing ring, the shadowy center, the asymmetry in brightness. Luminet’s simulated image had come, as he had suggested in the 1979 paper, extremely close to what we now know to be the supermassive black hole of M87.
The shot from Luminet’s hand-drawn simulation to the EHT image is just fabulous at many different levels. Scientific prediction and collaboration are the most important, but this points all that much more strongly to another key point: how all the work in theory paved a way for actual discovery to follow through.
We finally have direct visual evidence of a black hole. We now have visual evidence for a black hole; this one is located at the center of M87,” Doeleman said, confirming the very existence of a black hole at the center of M87. The finding presents the first visual proof for Einstein’s theory of general relativity and opens new doors for understanding these cosmic giants. The EHT team’s success involved a “Herculean task” in the collection and analysis of data, requiring more than half a ton of hard drives just to hold data from all of the observatories.
Not least with the help of Dr. Katie Bouman, whose algorithm stitched together formative data from all around the world to form the final image, that essentially turned our planet into a virtual telescope for that—without which something meaning to have a dish 10,000 kilometers wide, way beyond technological capability so far, is realized.
These discoveries do much more than take pictures. They open new routes into understanding the nature of black holes and how these cosmic objects impact their surroundings and orbiting galaxies. Indeed, this whirling material undergoing motion around a black hole is likely to form a set of light rings from which silhouettes may be easily transcribed to enable us to ‘see’ shadows of a black hole against the bright background made by its accretion disk.
Hence, next time you turn skyward into the night, remember that there, somewhere out in space, these mysterious giants are at work on the universe, shaping it, and it is thanks to early people like Jean-Pierre Luminet and the EHT team that we are now one step closer to unraveling their mysteries.
