Seeing is believing, say space enthusiasts around the world as they eagerly await the first ever true image of a blackhole, which could reveal the shape of the mysterious, warped region of the space-time fabric that has fuelled human imagination and inspired numerous sci-fi movies and literature for generations. Using data from six telescopes located across the world, the scientists involved in the Event Horizon Telescope (EHT) project have imaged the Sagittarius A* -- the blackhole located at the centre of the Milky Way galaxy—and another massive black hole 53.5 million light-years away in galaxy M87.
The results will be announced at 6.30 pm IST Wednesday. The gravitational pull of black holes lets nothing—not even particles and electromagnetic radiation such as light—escape from inside it. This makes imaging a blackhole nearly impossible.
Blackholes swallow the surrounding gas, which swirls around in a flattened disk, spiralling into it at speeds close to light. The radiation from this hot whirlpool, however, can be seen. Scientists have imaged this radiation, expecting to see the shadow of the blackhole against it.
“Basically, in the background light the shadow of blackhole can be seen. This is extremely important because although we had a lot of evidence about the existence of blackhole, but ‘seeing is believing’,” said Sudip Bhattacharyya, Associate Professor at Tata Institute of Fundamental Research (TIFR) in Mumbai.
“If we can directly see that there is something black in the background of light—that is an incredible thing. That would be the direct proof of blackholes,” Bhattacharyya told PTI.
The shadow is expected to reveal the outer most edge of the blackhole—known as the event horizon—helping scientists view the actual shape of a blackhole for the first time.
“For example if it is a rotating blackhole then it would not look like a perfect circle or disk. It will be somewhat oblate, or deformed. This deformation and how the light bends around the blackhole will reveal more information about the blackhole,” said Bhattacharyya.
Sagittarius A* has a mass approximately four million times that of the Sun, but it only looks like a tiny dot from Earth, 26 000 light-years away. To image such a large space object, scientists used a Nobel Prize winning concept called ‘Aperture Synthesis’, described by British astronomer Martin Ryle where data from many small telescopes placed far apart is combined.
The technique, which has been used to make radio images for many decades, provides results similar to using a single telescope as big as the area over which the smaller ones are located.
The ETH project used eight telescopes spread over different locations in the US, Chile, Spain, Mexico, Antarctica, Mexico, Denmark and France to create a result similar to having used an Earth-sized telescope.
“The blackhole itself is like a giant lens. The light coming from behind the blackhole will not come in a straight line, like usual, but bend around its edges,” Bhattacharyya said.
The distribution of the bent light, combine with the shape of the blackhole’s shadow, will give a lot of information about the blackhole and its gravitational properties. Space ensthusiasts took to Twitter to express their excitement as they count down to the moment.
“I think in human history we are the first generation to see the first ever picture of #Blackhole,” one user wrote.
“This is epic, legendary, totally mind blowing. The inner kid in me is jumping up and down,” another user said.
Some users pointed out how British physicist Stephen Hawking, who passed away last year, missed this historic moment. In 1974, Hawking for the first time predicted the existence of Hawking radiation which are released by blackholes.
The idea of a body so massive that even light could not escape was briefly proposed by astronomical pioneer and English clergyman John Michell in a letter published in November 1784. In 1915, German scientist Albert Einstein developed his theory of general relativity, having earlier shown that gravity does influence light’s motion. Further work on the theory of general relativity helped prove the existence of blackholes.