published on 11 April 2019 in space

Here is the first image of a black hole

Located more than 50 million light years away, at the centre of a gigantic elliptical galaxy called Messier 87, the first black hole to be immortalised in a photo: this object at a distance of 55 million light years from us has a mass equal to 6.5 billion times that of the Sun. Until recently, we were able only to see indirect proof of the existence of black holes, for example by looking for stars that seemed to orbit around strange objects or capturing the radiation emitted by the superheated material swirling around them.

The supermassive black hole at the centre of Messier 87. Credits: The Event Horizon Telescope

A black hole is the terminal phase in the “life” of a very big star which, after collapsing, turns into an extremely dense and compact body, a spacetime region characterised by extremely strong gravitational attraction. This makes a black hole an object able to “swallow up” everything that comes too close to it, including both electromagnetic radiation and matter, therefore. For this reason, it is technically impossible to observe black holes with our instruments: what the scientists have photographed is in fact the incandescent plasma surrounding the so-called event horizon, a sort of aura around the black hole beyond which even light cannot escape.

The image was obtained by the Event Horizon Telescope (EHT), a group of eight ground-based radio telescopes located in various parts of the planet, giving rise to an Earth-sized virtual telescope and obtaining an instrument with unprecedented sensitivity and resolution. The EHT is the result of years of international collaboration and offers scientists a new way to study the most extreme objects in the Universe predicted by Einstein’s theory of general relativity. EHT collected over a petabyte of data to photograph the M87 black hole in April 2017. It took over two years of work by a team of more than 200 researchers to obtain the image of the black hole.

The network of EHT radio telescopes. Credits: Eso/O. Furtak

This incredible result, which represents a historical milestone for astronomy, was published in a special issue of The Astrophysical Journal Letters: six articles describe the feat that led to obtaining the image of the black hole and the details that the photo reveals to us.

“The great innovation of the first photograph of a black hole is that cosmic objects that are by definition invisible, for the first time can be seen and studied directly. Now we can finally observe them. This is the first page in a book in which it is possible to make increasingly more accurate observations of these objects, predicted a century ago by Albert Einstein,” said Professor Luciano Rezzolla, Director of INFN in Frankfurt and member of the EHT collaboration scientific committee. This discovery, therefore, besides once more demonstrating the validity of Albert Einstein’s theory of general relativity, is the starting point on the road to understanding our universe.

For further information:
The first picture of a black hole has been taken

Get more information with Eniscuola: 14 September 2015: the discovery of gravitational waves

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