by Katelynn Fleming
Ever seen a picture like the one above when describing a black hole? It may not be hard to believe that this one is an artist’s rendering of a black hole–not the real thing–but did you know that we have actually never before photographed a black hole? This year, a global initiative called the Event Horizon Telescope may bring us our first ever real image, which will allow scientists to put Albert Einstein’s theory of general relativity to the most stringent test yet. These results could change the way we look at the universe if they contradict Einstein’s predictions or allow us to proceed with more certainty if they support it.
The problems with photographing a black hole are manyfold. There is interstellar dust that gets in the way of our observations and makes the black hole a blurry disc of light instead of a defined accretion disk (the swirling matter around the black hole which is millions of degrees Fahrenheit) and the shadow of the black hole. Next, it would require a telescope with an aperture, lens diameter, equal to the diameter of the Earth to resolve the event horizon of the black hole. Even if you are totally out of the loop on astronomy, you probably know that we do not have anything near that size.
However, courtesy of modern technology and human ingenuity, researchers in the Event Horizon Telescope project have found a way to get around these issues. To address the interstellar dust that absorbs visible light, they have painstakingly searched for and found a wavelength of radio wave radiation that is not absorbed by the dust, and thus passes through to be picked up by human radio dishes. A telescope the size of the Earth was a little harder to get around, but instead of building one huge apparatus, researchers have observed the black hole from seven existing radio telescope arrays across the globe simultaneously to create data that can be synthesized into cohesive images using advanced computer programming.
In April 2017, the observations themselves took place with all arrays simultaneously pointed at Sagittarius A, gathering as much data as possible. In total, they collected one petabyte of information, which Newsweek puts in perspective: “a petabyte of MP3 songs would play continuously for more than 2,000 years without repeating.” The vast amount of data had to be transported on disk drives by plane, boat and train to MIT Haystack Observatory for processing. The South Pole data did not even arrive until December as no planes could fly it out until the winter had passed (in the southern hemisphere the winter is during our summer). Now, the data is being fed into supercomputers which will remove error due to the different locations of the observation sites and the spin of the Earth, and then it will be sent to the Max Planck Institute in Germany to be further analyzed.
Right now, researchers are still working to compile the images from the radio wave data. When it is completed, we will have the best resolution of a black hole that we have ever seen.
When the images finally come out, astrophysicists will have the observations to test Einstein’s theory of general relativity at the most extreme level. General relativity applies to large objects with gravity, but does not account for quantum level interactions. The nature of a black hole requires understanding of both high gravity and very small quantum particles, so it is an ideal phenomenon to test and hopefully eventually unify the theories. Researchers will look at the actual shape and size of the black hole and compare it to the predicted values of general relativity. If the observations disagree with relativity, Einstein’s theory could come crashing down and we would have to re-conceptualize how we think about the universe.
The final images are scheduled to be released this year. Stay tuned for an update when they are!
