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Can you photograph a black hole?

In 2018 we could count on the first radio wave image of the event horizon of Sagittarius 43, at the center of our galaxy, the Milky Way.

Black hole
Black hole

At first glance it seems an impossible challenge. How can you photograph a place from which even light can not escape? Over the years and thanks to radio telescopes, we have been able to make a more or less detailed image of  stellar black holes, which appear when a very massive star ends its existence. But there are others of another type. These are objects that are at the center of galaxies like ours and those that we know about indirectly: supermassive black holes. The one of the Milky Way, in particular, is known as Sagittarius A.

In April 2017, an international group of astronomers pointed out to Sgr A * a series of radio telescopes distributed all over the world that form the so-called Event Horizon Telescope (EVT). Its objective is to obtain a most realistic image of the so-called event horizon, the region that marks the limit of what is visible around the black hole. Or what is the same, the point of no return, because once that border is crossed, the speed necessary to escape the gravitational attraction of the hole is greater than that of light. For six nights, the EVT was observing the center of our galaxy. The collected data is being processed and, if all goes well,in 2018 we could count on the first image – on radio waves and not very clear – of the aforementioned event horizon.

Most galaxies in the universe have a black hole in their center, like ours, and some of them even have two. These black holes would generate  enough gravity to maintain the unity of the galaxy itself. For example, the Andromeda galaxy  is a neighbor of our galaxy, 2.5 million light years away. The black hole at its center is about 30 million times more massive than the Sun and about 10 times more massive than the central black hole of the Milky Way.

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Photographing the event horizon, the limit after which matter disappears when hitting it, now seems more coherent than ever, given that it has recently been proven that it really exists . The test consisted in trying to verify the hypothesis that black holes have a solid surface. Not finding evidence of that surface indicates that there is an event horizon, which is a strong check for scientists. The same is true for Einsten’s Theory of Relativity.

This means that the event horizon is no longer an imaginary, but not physical, boundary, from which incoming light can no longer escape.

Although we know more and more about black holes, and that does not stop being one of the most mysterious objects in the universe, they are also the simplest and because? Because almost all the rest of the bodies of the universe are governed by different forces that we have to explain with particle physics, such as thermodynamics and magnetism. However, black holes are governed only by one force: gravity.


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