On April 10, the international collaboration of the world’s astronomers successfully shot the picture of a black hole which is in the center of the giant galaxy, M87. This observation, which began on April of 2017, was accomplished for the first time in two years. It was a momentous occasion. As astrophysicist Sheperd Doeleman, director of the Event Horizon Telescope put it, “We have achieved something presumed to be impossible just a generation ago.”
That seeming impossibility was due to black hole’s unique properties. Since the black holes are so strong and they suck all light that comes in, the direct observation of them poses a challenge. However, the special telescope named Event Horizon Telescope (EHT), allowed scientists to take an image of a black hole’s shadow. It is kind of a virtual telescope with nine different radio telescopes in the world, located in the United States, France, South Pole, Chile, and so on, that are connected together to perform as one huge scope the size of Earth. It has enough resolution to read newspapers in New York from a cafe in Paris. The propagation signals of the black hole that the nine telescopes collect are integrated into the computer, which traces them back to film the black hole. At the end, the specialized supercomputers located in the Max Planck Institute for Radio Astronomy in Germany and the MIT Haystack Observatory in the United States, converted the original data into final images. The supercomputers revealed the circumference of the black hole’s event horizon (the boundary area of the black hole) as 40 billion kilometers, and the shadow of the black hole as 100 billion kilometers.
The black spot in the middle of the picture is the black hole’s shadow containing the black hole, and the reddish loop surrounding the black hole is the light that was bent by its gravity. This black hole is 55 billion light years away from the Earth, and it is 6.5 billion times heavier than the Sun. As previously mentioned, black holes can absorb every electromagnetic radiation including light, therefore, direct observation is impossible. The Event Horizon Telescope indirectly shot the boundary area which is the horizon of events that was affected by the gravity of the black hole and the electromagnetic radiations. The gravity of a black hole bends the light around the horizon of events, and these distorted lights illuminate it.
“Today, general relativity has passed another crucial test, this one spanning from horizons to the stars,” said EHT team member Avery Broderick.
The historic observation of the black hole was enough to bolster Albert Einstein’s 1915 theory of general relativity. Einstein did not directly suggest the idea of black holes at that time. However, the following year, German physicist Karl Schwarzschild solved the equation of general relativity, which said that space-time can be warped, and made a mathematical concept equivalent to a black hole. This theory was first demonstrated in 1919 by observing a total eclipse of the Sun, and this observation proved that Einstein’s theory of general relativity was valid.
One of the EHT team members said that they are planning to get a video of what happens at the site of M87 as their next step. They also mentioned that they found the black hole Sagittarius A, at the center of the Milky Way, and they expect to see the image after analysis. They are now getting worldwide spotlight, and their future course of action is expected to develop our science greatly.