On April 10, 2019 astronomers revealed the first ever black hole image in the history. It was photographed by the Event Horizon Telescope (EHT), a network of eight linked telescopes across the world. The image shows that the black hole is at the heart of the galaxy Messier 87(M87) which is approximately more than 50 million light-years away containing the same mass as 6.5 billion suns.
The first image of a black hole, situated at the center of the galaxy M87; Image Source: eventhorizontelescope.org
This gigantic black hole is like a beast that swallows anything that comes too near. Stars, planets, gas and not even light escapes the beast’s grasp once it crosses a threshold called the event horizon.
This image is an astonishing accomplishment of the Event Horizon Telescope(EHT) project, a project which is a global collaboration of more than 200 scientists. The effort to capture the image, using telescopes in locations ranging from Antarctica to Chile, involved a team of all those scientists.
The Event Horizon Telescope array, a planet-scale array of eight ground-based radio telescopes forged through international collaboration ; Image Source: www.bbc.com
“We have taken the first picture of a black hole”, said EHT project director Sheperd S. Doeleman of the Center for Astrophysics | Harvard & Smithsonian. “This is an extraordinary scientific feat accomplished by a team of more than 200 researchers”, he added.
The EHT used a technique called very-long-baseline interferometry (VLBI) which synchronized telescope facilities around the world and made it an earth-sized telescope. The telescopes used t make this giant telescope were not physically connected but were able to synchronize their recorded data.
Atacama Large Millimetre/sub-millimeter Array (ALMA) , Chile, one of several telescopes across the globe that make up the Event Horizon Telescope ; Image Source:www.nytimes.com
EHT collected data at a wavelength of 1.3 mm during a 2017 global campaign. Each telescope of the EHT produced immense amounts of data which took two years for scientists to assemble. The amount of data was too enormous that the team had to move its information from place to place the old-fashioned way.
“There’s no way that we can transfer this data through the internet”, EHT project scientist Dimitrios Psaltis, an astronomy professor at the University of Arizona, said at the SXSW event. “So, what we actually do is, we take our hard drives and we FedEx them from place to place. This is much faster than any cable that you can ever find”, he added.
Dr. Katie Bouman, who developed the algorithm that pieced together the data from the EHT rendered the black hole image; Image Source: www.bbc.com
The image that we saw was generated using series of algorithms which pieced together the data from the EHT. Dr. Katie Bouman, Assistant Professor of Computing and Mathematical Sciences at the California Institute of Technology, started making those algorithms three years ago while she was a graduate student at the Massachusetts Institute of Technology (MIT).
In computer science and mathematics, an algorithm is a process or set of rules used to solve problems. The image was rendered by Dr Bouman’s algorithms, means series of algorithms converted telescopic data into that historic photo. After few hours of the photo’s significant release, Dr Bouman became an international sensation, with her name trending on every social media. But she insisted that the team that helped her deserves equal credit. “No one of us could’ve done it alone”, she told CNN. “It came together because of lots of different people from many different backgrounds”, she added.
Before now, people could only think of black holes in theories and movies. Black holes are some of the strangest and most fascinating objects found in outer space. They are objects of ultimate density, with such strong gravitational attraction that even light cannot escape from their it. To be very specific, there are three kinds of black hole: stellar black holes, supermassive black holes and intermediate black holes.
Zoomed out view of the supermassive black hole which is lying at the center of M87 galaxy, captured by EHT; Image Source: futurism.com
When a larger star collapses, it continues to compress and creates a stellar black hole. These black holes are (relatively) small, but incredibly dense. Then comes the Supermassive black holes. supermassive black holes are millions or even billions of times as massive as the sun.
Such black holes are thought to lie at the center of pretty much every galaxy, including the Milky Way. So it is pretty much obvious that the black hole whose image was captured is a supermassive black hole itself. The intermediate black holes are nothing but mid-sized black holes which are created when stars in a cluster collide in a chain reaction.
Black holes themselves are invisible, then how is it possible to identify their existence? It is claimed that, their presence exerts a powerful gravitational force near the Event Horizon on nearby gas and stars, causing everything to orbit at tremendous speeds. It accelerates until it approaches the speed of light and in the process acquires tremendous energy. Some of this energy is converted into radiation and forms an accretion disk around the black hole which indicates the existence of a black hole.
Prof Sheperd Doeleman of the Harvard-Smithsonian Centre for Astrophysics described the achievement as “an extraordinary scientific feat”. “We have achieved something presumed to be impossible just a generation ago”, he said. The team is also imaging the supermassive black hole at the center of our own galaxy, the Milky Way.