In April 2019 humanity witnessed the first-ever real image of a black hole. The black hole, named M87 was observed by the Event Horizon Telescope.
The feat marked how far our technology has come. Even though the resulting image was blurry owing to low resolution, it remains an ingenious scientific achievement. It also told us how far we have to go from here, to create an even better image of the black hole.
Shortly after that, in September 2019, Nasa created a visualisation of an actively accreting supermassive black hole – how it will look under better resolution. It looks simply stunning.
Ever since black holes came into the world of science, -first as a theoretical entity predicted by Einstein’s general theory of relativity-, it has garnered the undivided attention of masses of scientists.
Black holes are known for their massive gravitational fields, something which even light cannot escape. Most large galaxies have a supermassive black hole sitting right at its centre, almost as an invisible hand keeping the stars of that system in place.
We don’t know much about black holes for sure. Our knowledge of it is as dark as the entity itself. But with each passing year little by little, we are learning about this powerful celestial body.
The first-ever simulated image of a black hole was created using calculations made on a 1960s punch card IBM 7040 computer. The simulation was plotted by hand by French astrophysicist Jean-Pierre Luminet in 1978. As remarkable as it may sound, what Luminet had simulated then looks a lot like the very recent simulation by NASA.
Both simulations have a black circle in the centre. That’s the event horizon, the point at which electromagnetic radiation – light, radio waves, X-rays – are no longer fast enough to achieve escape velocity from the black hole’s enormous gravitational pull.
Across the middle of the black hole, is the front of the disc of material that is swirling around the black hole, just like how water goes into a drain. Intense radiation this region produces is what helped us detect the M87 with our telescopes.
A photon ring can be seen around the event horizon- like a perfect ring of light. A broad sweep of light can be seen around the black hole. It comes from the part of the accretion disc behind the black hole; but the gravity is so intense, even outside the event horizon, that it warps spacetime and bends the path of light around the black hole.
It is through simulations such as these we get to learn and understand more about physics that makes a black hole exist. The same simulations have helped us know which is what when we observed M87 for the very first time.
Even if you were to take out the complex calculations and hard physics from the black hole, it still remains grandiose – a visual delight. Beautiful and horrifying at the same time.