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Seeing the unseeable: First image of a black hole released

Scientists had to build an elaborate and complex network of massive telescopes around the world, and devise ingenious new techniques, to piece together a picture that now provides the first visual evidence of a black hole.

Written by Amitabh Sinha | Pune |
Updated: April 11, 2019 12:08:44 pm
Seeing the unseeable: First image of a black hole released The first image of a black hole, from the galaxy Messier 87. (Source: NYT)

Astronomers on Wednesday unveiled the first-ever direct image of a black hole, more than 100 years after these super-dense extreme-gravity regions of space-time were theorised as a consequence of General Theory of Relativity.

The spectacularly bright-orange circular image with a dark central region was taken by the Event Horizon Telescope (EHT) Collaboration in April 2017, and revealed simultaneously at five press conferences in four different continents on Wednesday evening.

Black holes, those unimaginably dense regions of space-time from where even light is unable to escape, are formed mainly by massive collapsing stars after they start extinguishing. The space-time around them gets so incredibly bent that nothing is able to escape from its gravity.

The black hole, whose image was captured, is located at the centre of the Messier 87 (M87) galaxy in the Virgo galaxy cluster. The black hole is at a distance of 55 million light-years from earth and has a mass 6.5 billion times that of the Sun. Scientists have also captured the image of another black hole, Saggitarius A*, which is very much in our own galaxy, the Milky Way, but that image is not as sharp as the one released Wednesday and needs further processing.

It is not that black holes have been discovered for the first time. Quite the contrary. Scientists have gathered a pile of evidence from a variety of experiments over the decades that showed that black holes exist. They have not only been able to locate them in the universe but also calculated their sizes, masses and the impacts they have on their surroundings and other heavenly bodies.

Explained: Here is a black hole, and why none was photographed before

However, since these black holes are completely ‘dark’, and do not emit or reflect any light, nor any other electromagnetic radiation, they could not be ‘observed’ by any of the scientific instruments.

Scientists had to build an elaborate and complex network of massive telescopes around the world, and devise ingenious new techniques, to piece together a picture that now provides the first visual evidence of a black hole.

“We have been studying black holes so long that it is easy to forget none of us has ever seen one before,” said France Cordova, director of the National Science Foundation of the United States.

Sheperd S Doeleman, EHT Collaboration director, said the existence of black holes was now proven without any doubt. “We have today seen what we thought was unseeable,” he said.

Read | The image of a Black Hole’s event horizon was made possible by this MIT grad student’s work

The Event Horizon Telescope comprises of eight radio telescopes — located in Hawaii and Mexico, in the mountains of Arizona, in Spanish Sierra Nevada, in the Atacama Desert of Chile and near the South Pole in Antarctica — which captured very high frequency microwave radiation that had originated from near the black hole 55 million years ago. Each of these telescopes captured only a small piece of the area. The data from all those were then feeded into a central super-computer which, over several months, created a complete picture.

The outer orange disk in the image represents the radiation being emitted by gases and other objects that exist just outside the black hole. The inner dark circular area in the image is actually the black hole.

“It is the result of an incredible piece of science and engineering. This particular photo is the highest resolution picture ever taken by anyone anywhere in the universe,” Somak Raychaudhury, director of Pune-based Inter-University Centre for Astronomy and Astrophysics, said.

Also read | Black hole event horizon: Here is what it looks like

Scientists said the image captured by the telescopes matched computer simulated images, created using mathematical models, in many respects, and therefore, corroborate the scientific theories, especially the General Theory of Relativity. But there were important differences as well. “For example, if you have seen Interstellar movie, there is an image of a black hole that has been used. That image was created using our existing theoretical knowledge. Someone of the stature of (Nobel prize-winning scientist) Kip Thorne was associated in creating that image. That image is slightly different than the one that we saw today. So maybe this image will reveal some new things about physics,” Raychaudhuri said.

The unveiling of the black hole image comes three years after scientists, in a similar global announcement in Feb 2016, reported the discovery of gravitational waves, another prediction of the General Relativity. The first gravitational waves to be detected was produced by an event in which two black holes had merged into one 1.3 billion years ago. Several more gravitational waves have been detected after that.

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