Black Hole Breakthrough Bags This Year’s Nobel Prize

Written By Sneha Senthilkumar (Grade 11)

With a winning streak of two ‘Nobel Prize in Physics’, the department of astronomy has set the bar high yet again. Last year, the award was given for the discovery of an exoplanet orbiting a solar-type star. This year, the award has been given for “the discovery of a supermassive compact object at the centre of our galaxy”. This ‘compact object’ that is being referred to as a black hole.

Half of the Nobel Prize was given to Roger Penrose, an English mathematical physicist. Reinhard Genzel, a German astrophysicist as well as the co-director of the Max Planck Institute for Extraterrestrial Physics, shared the other half of the prize with Andrea Ghez, a professor in Department of Physics and Astronomy at UCLA. 

So, what was so amazing about 2020’s Nobel Prize in Physics? Here is everything you need to know about the groundbreaking research done by these physicists and their teams, finally driving the nail in the coffin for the existence of supermassive black holes in the middle of our galaxy and others similar to our own.

Roger Penrose and Stephen Hawking predicted the theory suggesting the existence of black holes. The duo had used Einstein’s theory of general relativity to mathematically prove the existence of these astronomical objects. However, black holes were not taken seriously back in the ’60s and ’70s, as they were very theoretical. There had to be evidence, something to back up their postulation if it were to hold significance in the science community.

So, as the years passed, and there were more technological advancements, making data collection in astronomy more feasible. While Penrose had secured the theoretical aspect, Ghez and Genzel took care of the observational part, hoping to prove that there are truly supermassive black holes in the centre of our Milky Way. Both physicists used infrared telescopes. The reason for choosing infrared specifically is because its longer wavelength enables it to get by the dust that is found very concentrated in the centre of our Milky Way. They used these telescopes to track the position and velocities of stars near the centre of our Milky Way, using which we can determine the orbit of those stars, and consequentially the mass of the object it orbits.

From 1992 to 1996, Prof. Reinhard Genzel and Prof. Andreas Eckhart used the NTT (New Technology Telescope) in Chile to observe the position and motion of ten stars. With the collected data after four years of research, they estimated the mass of the object at the center to be 2.45 (±0.4) million times the mass of the sun. They were pretty sure that it was a black hole. 

But science is not very forgiving, and one piece of evidence is not enough to prove such an abstract theory. Therefore Prof. Andrea Ghez and her team at UCLA did the same but increased their precision using the high-resolution Keck Telescope at Hawaii. This telescope uses lasers, which observes the turbulence in the atmosphere in the centre of our Milky Way. That turbulence actually disrupts the light emitted by the stars, which they were observing. The method is to subtract the turbulence from the observations, which results in way more accurate data. Prof. Ghez and her team observed over 500 stars for a long 12 years, from 1995 to 2007. Finally, they calculated the result for the mass of the object in the centre of the orbit of these stars at the centre of our Milky Way to be 4.5 (± 0.4) million times the mass of the sun. 

I want you just take a second and let that number sink in. It’s hard to even imagine it, isn’t it? It was a black hole. No doubt. Anything greater than five solar masses had the power to collapse into a black hole. So the number received by both Ghez and Genzel was utterly shocking and too real to be true. 

The discovered black hole was indeed a supermassive black hole, named as Sagittarius A*. The first image of a black hole in 2019 only gave the final blow to confirm the existence of these mind-bending bodies found in space.

The sheer determination and will power of these scientists is truly inspiring, and this year will send their names through history. They have dedicated their whole lives in pursuit of the answer to this one question, and it is safe to say that all their blood, sweat and tears have paid off. I think, that the most important thing we should be taking from this year’s Noble Prize Winners, is to never give up on something you believe in. These people are living proof that have shown that no matter who you are if you set your mind to something, with hard work and perseverance, you can achieve anything. And nothing can stop that.

Featured Image Courtesy – Physics World