According to general theory of relativity (published in 1915 by flamboyant scientist Albert Einstein) every Galaxy is having a Black Hole at the centre of it. Our Galaxy which is known as the Milky Way (diameter: 1,00,000 light years) is also having a Black Hole at the centre of it. It’s Sagittarius A*. Sagittarius A* is 25,640 light years away from the Earth. The photo of a Black Hole we captured is located at the centre of the Galaxy M87 (diameter: 4,90,000) scientists have named it “Messier 87”. This Messier 87 is 5.5 crore light years away from the Earth, which means the photo we captured is 5.5 crore light years old. Messier 87 is supermassive typed Black hole (there are three types of Black Holes: Stellar black holes, Supermassive black holes, Miniature black hole).
There are couple of questions we need to dig up to understand the whole process.
True. Black Hole is not visible, even light can not escape from it. Light’s main element is photon, and photon has no mass, then how gravity of a Black Hole is influencing the light? Well that’s a million dollar question. And so simple answer is this: According to the general theory of relativity, gravity affects anything with energy. While light doesn't have mass, it still has energy – and its thus affected by gravity. Light travels in a straight line, straight lines are no longer straight if exposed to a strong gravitational force; instead, they are curved.
When the light is inside the black hole, it experiences immense gravity, increasing every second by a billion times.
When light passes from near a black hole it starts rotating around black hole at the rate of not lakhs but crores of kilometres per hour. Then atoms of light stumble upon each other and get ignited with lakhs of Celsius heat. This combusted heat generates a lighting circle around the black hole, this is what is known as the event horizon. Anything goes inside the event horizon, it’s gone and disappears.
Two reasons,1). Hubble is optical telescope, it can capture visible lights. However to capture a picture of an element which is 5.5×9,46,10,00,00,000 km away from Earth. Which means there will be millions of asteroids and other cosmic substance will come along the way, to penetrate them is out of the scope of the Hubble telescope.2). To take a picture for the substance which is 5.5 crore light years away, there must be two conditions matched.
1… In place of optical, it requires Radio telescope because x-rays and gamma rays are having high frequency.
2… Messier 87’s diameter is 0.011 light year and it is 5.5 crore light years far from Earth. To get a photo of this small and this far situated element, it requires a huge antenna. An antenna which is having minimum of 12,700 km of diameter. This means it requires a telescope which is as big as Earth. It is not possible to build such huge construction. So scientists have simulate the Earth sized telescope by using a technique called “interferometry”.
Okay. So basically what scientists have done is, they placed 8 telescope around the globe (5 continents) and aligned their radar towards the Messier 87. These 8 telescopes supposed to receive the radio waves from the cosmos, so they interfere the signals received by each of them and together they picture as a whole. The amount of data they received was mammoth sized, it was receiving 16 gigabyte per second, they received signals for 10 years. One after another hard drives were getting cram. The total weight of the hard drives was 500 kgs. The size of the binary data was 5 petabytes. Converting those binary into image was the achievement one of its kind in the computer science world. These data were sent to the data center’s in Germany and Boston, where they got decoded by using CHIRP (Continuous High-resolution Image Reconstruction using Patch priors) algorithm. CHIRP algorithm is written by an American computer scientist Katie Bouman. She is considered the brain behind this photo of Black Hole.
