Explained.
Astronomers on Wednesday unveiled the first photo of a black hole, one of the star-devouring monsters scattered throughout the Universe and obscured by impenetrable shields of gravity.
The image of a dark core encircled by a flame-orange halo of white-hot gas and plasma looks like any number of artists' renderings over the last 30 years. But this time, it's the real deal.
1. How it was done
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The fact that black holes do not allow light to escape makes viewing them difficult. The scientists look for a ring of light - disrupted matter and radiation circling at tremendous speed at the edge of the event horizon - around a region of darkness representing the actual black hole. This is known as the black hole's shadow or silhouette.
Astrophysicist Dimitrios Psaltis of the University of Arizona, the EHT project scientist, said, "The size and shape of the shadow matches the precise predictions of Einstein’s general theory of relativity, increasing our confidence in this century-old theory."
"Imaging a black hole is just the beginning of our effort to develop new tools that will enable us to interpret the massively complex data that nature gives us," Psaltis added.
The project's researchers obtained the first data in April 2017 using telescopes in the U.S. states of Arizona and Hawaii as well as in Mexico, Chile, Spain and Antarctica. Since then, telescopes in France and Greenland have been added to the global network. The global network of telescopes has essentially created a planet-sized observational dish.
Knit together "like fragments of a giant mirror," in Bremer's words, they formed a virtual observatory some 12,000 kilometres across -- roughly the diameter of Earth.
In the end, M87 was more photogenic. Like a fidgety child, Sag A* was too "active" to capture a clear picture, the researchers said.
"The telescope is not looking at the black hole per se, but the material it has captured," a luminous disk of white-hot gas and plasma known as an accretion disk, said McNamara, who was not part of the team.
"The light from behind the black hole gets bent like a lens." The unprecedented image -- so often imagined in science and science fiction --- has been analysed in six studies co-authored by 200 experts from 60-odd institutions and published Wednesday in Astrophysical Journal Letters.
"I never thought that I would see a real one in my lifetime," said CNRS astrophysicist Jean-Pierre Luminet, author in 1979 of the first digital simulation of a black hole
The project's researchers obtained the first data in April 2017 using telescopes in the U.S. states of Arizona and Hawaii as well as in Mexico, Chile, Spain and Antarctica. Since then, telescopes in France and Greenland have been added to the global network. The global network of telescopes has essentially created a planet-sized observational dish
(Picture: elescopes located in different parts of the world)
2. Seeing is believing
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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 some what oblate, or deformed. This deformation and how the light bends around the blackhole will reveal more information about the blackhole," said Bhattacharyya.
3. What are black holes?
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Black holes, phenomenally dense celestial entities, are extraordinarily difficult to observe despite their great mass. A black hole's event horizon is the point of no return beyond which anything - stars, planets, gas, dust and all forms of electromagnetic radiation - gets swallowed into oblivion.
"This is a huge day in astrophysics," said U.S. National Science Foundation Director France Córdova. "We're seeing the unseeable."
The fact that black holes do not allow light to escape makes viewing them difficult. The scientists look for a ring of light - disrupted matter and radiation circling at tremendous speed at the edge of the event horizon - around a region of darkness representing the actual black hole. This is known as the black hole's shadow or silhouette.
4. How far is it?
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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.
5. Space geeks freak out
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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. PTI
