Scientists have created history by capturing the first-ever image of a black hole event horizon, which holds the key to one of the biggest mysteries of the cosmos.
“We have now seen the unseeable," said Shep Doelman, director, Event Horizon Telescope (EHT), when he released the images of the black hole, which has a mass 6.5 billion times that of the sun and is situated 500 million trillion km away in the M87 galaxy.
A black hole is one of the most exotic astronomical objects, often called “the place of no-return", with a gravitational pull so strong that it does not even allow light to escape. An event horizon is the region of space beyond the black hole, a place where laws of physics cease to operate.
“So far, what we know about a black hole and its structure is theoretical, based on gravitational waves. Observationally, we have explained various phenomena on the basis of their existence. However, no one has seen what it actually looks like," said professor Nirupam Roy of the Indian Institute of Science (IISc), Bangalore, terming it as a major breakthrough, which will be the beginning of a better understanding of the universe.
Scientists across the globe collaborated for the project, called the Event Horizon Project (EHT), as eight telescopes from different locations combined to create a virtual telescope as large as the earth, using a technique called interferometry.
The images were taken at the same time in April 2017, attaining precision using atomic clocks. The images released on Wednesday showed a bright ring at the centre of galaxy M87, which has been formed by the superheated gases falling into the black hole.
“What we saw were the edges of the black hole. A black hole does not let light escape, so it’s difficult to identify its existence, compared to any other empty space. However, in this experiment, the radiations coming from the matter behind the hole reached us cutting out a dark circular hole. The shape is the shadow of the black hole," said Patrick Das Gupta, professor at Delhi University’s department of physics and astrophysics.
It was also the first time that Albert Einstein’s theory of relativity, an important tool in understanding the universe, was put to a direct test. If the images had not conformed to the theory and the shadow was not spherical, it would have meant that Einstein’s theory was not correct.
“The shadow of the black hole is nearly circular, which is consistent with our simulations. The theory has passed the crucial test," said Avery Brider, scientist, EHT.