GoT, BTS comeback, Endgame, Sacred Games and all are cool, but if you weren’t hyped for the revelation of the century then that’s something very, very sad! We finally have the real deal guys!
We have known that black holes existed since a long time but what we had been looking at so far were simulations and artistic renderings just like how our artists imagined what ‘Curiosity’ looked like on Mars, which is why we forgot we hadn’t really seen what a black hole really looked like.
‘A literal heart of darkness’, that’s how the dude in Interstellar described the black hole ‘Gargantua’ (also a wonder of computer graphics). But then the question arises how we knew black holes were really hearts of darkness, especially when we had never seen one before. To know the answer, buckle up for one stellar ride!
One ring to rule black holes:
The idea that a black hole existed can be traced back to the 1780s Cambridge where John Michell first thought of ‘dark stars’ as massive stars which had the power to stop light. Along with him Laplace also believed that such astrophysical bodies existed. But it was Einstein who made the world look at gravity, mass, space and time through the glasses of his theories: theory of general relativity and theory of special relativity. Thus we came to know about space-time and the distortion in space-time which brings into picture Karl Schwarzschild. He provided mathematical solutions to Einstein’s field equations and it was this solution which basically explains the special case of distortion of space-time near an extremely massive albeit tiny object. This basically means that they predicted the existence of black-holes and also that such black holes at their core encase singularity –a region where all our laws as we know them to break down.
Sounds blasphemous no? Well it certainly was for physicists at that time but then with accurate maths staring at them in the face, it becomes slightly hard to argue… you just learn to live with it. Even Einstein wasn’t too excited about the idea.
Then in 1971, much to chagrin of many scientists and delight of believers, we discovered our first black hole with a lot of X-Rays involved in process but we still didn’t have a picture!
Frankly, a black hole is supposed to a ‘black hole’ literally, so it was impossible to capture it at all. Although what was possible, was capturing the event horizon. Theoretically –boundary around the black hole where photons enter but can’t escape. The matter surrounding the black hole is pulled into it and forms a disk around which speeds up and glows due to high temperature. This light, when pulled towards the black hole, is sucked in, but not all of it. Some rays of light which travel at a certain distance, bend around the periphery closely and that makes us possible for us to see the event horizon –the ring to rule everything around it including matter and light.
One ring to find black holes:
Our galaxy alone has millions of black holes but they are millions of light years away which makes it kinda difficult for us to observe. Sagittarius A* the black hole at the center of Milky Way is 26,000 light years away. So to observe the event horizon we needed a massive telescope, almost of the size of the planet alone i.e. we needed an instrument with Earth-sized aperture. Sounds impossible? But then what good is a science person who doesn’t challenge the ‘impossible’?
So some smart people decided to do an international collaboration to see the unseen. Taking into account the rotation of Earth, if a lot of giant telescopes worked together we would have a result similar to an Earth-sized telescope. The main objective was to operate ‘within a range of electromagnetic spectrum’ so that nothing hampers the light we receive from the event horizon and to get high-resolution images. It was achieved through 8 observatories situated around the globe. The logic being, the rotation of Earth would make the observatories change positions while focusing on the supermassive black hole. Thus we would be collecting data for the same image from different spots! Initially, 11 observatories were planned to participate however only 8 did, including one in the South Pole.
This collaboration is called The Event Horizon Telescope, which successfully captured the image of the supermassive black hole at the heart of galaxy Messier 87.
One ring to bring them together!
‘Looking at the event horizon from Earth is like looking at an orange on the surface of moon.’
That is what Katie Bouman said in her Ted Talk while explaining how to picture a black hole. But then we solved the resolution part with EHT.
The new problem was to make sense of the data we received. That’s where Bouman comes in. She developed the algorithm which ‘finds the most reasonable image.’ With the limited data and given the fact that we had never seen a black hole before plus we weren’t sure whether Einstein’s theories really did hold true in extreme conditions like black hole’s environment, we didn’t want a prejudiced image. So without assuming too much, they brought together the images, parts of images and reconstructed them within the measurements of the telescope to get one final picture.
And into the darkness bind them!
It might not be as bright like Gargantua in Interstellar but it was definitely more surreal to look at the real deal against the backdrop of darkness.
‘It’s never a good idea to bet against Einstein,’ said the Director of EHT, Shep Doeleman. Truly, it isn’t a good idea because in the end we did see what we hoped to see –a supermassive blackhole (SMBH) with a lopsided ring of light surrounding it –the last photon orbit. ‘The evidence of event horizon’.
Technically what we did look at was the ‘silhouette or shadow of black hole surrounded by luminous plasma’ as The Astrophysical Journal Letters put it and so ‘Einstein Rules!’ as Priyamvada Natarajan tweeted.
The image was that of the SMBH churning in a clockwise direction at the heart of M87 galaxy. The black hole at the heart of our galaxy was also supposed to be captured but it wasn’t stable enough to be caught in a photogenic moment. Along with EHT, NASA’s Chandra X-ray observatory had also observed the same black hole but not close enough.
If you think about it, what we looked at was the picture of the black hole which existed 55 millions of light years ago –we basically looked back in time when human life wasn’t even present on Earth. Aren’t you glad to be born in this era to witness something Stephen Hawking would be proud of?
To be the first generation to see the first real image of a black hole, to realize that we have come such a long way from the first step on the moon. Next up we have more black holes, quasars to observe and the whole universe to dive into. Mankind continues to take giant leaps into infinity and beyond!