For the first time astronomers have succeeded in making an image of a black hole – and as predicted by theory, it is surrounded by a halo of hot gas. The black hole is in the galaxy M87 at a distance of about 54 million light-years. This galaxy was included by the French astronomer Charles Messier in 1774 in his catalogue as number 87.


The image was made using the Event Horizon Telescope (EHT), a network of eight linked radio telescopes spread across the Earth.
Since the resolving power (the smallest details still visible) is directly related to the diameter of a (radio) telescope, it is true in astronomy that ‘bigger is better’. However, there are practical limits to the size of a single telescope; that is why a technique called aperture synthesis was used here. With this, different telescopes, widely separated from each other, form a virtual telescope that is as big as the Earth.

A single radio telescope is not able to create an image of the black hole. The researchers linked eight telescopes that are spread across the entire Earth (illustration: BBC).

A team of 200 researchers pointed the linked telescopes during a period of 10 days to the heart of M87, and collected so much data that it had to be physically (on hard discs) flown to Boston (USA) and Bonn (Germany) for processing.


The black hole has a diameter of about 40 billion kilometres and a mass of about 6.5 billion times that of the sun. In the words of professor Heino Falcke from the Radboud University in Nijmegen, Holland, who proposed the experiment: “It is one of the heaviest black holes that we think exists. It is an absolute monster, the heavyweight champion of black holes in the Universe.”


The black hole appears as astronomers (and also Hollywood directors) have always imagined. It therefore appears that Einstein was correct once again.
Nevertheless, not all questions have been answered by a long shot – black holes are and remain extremely mysterious objects. For example, it is still not known how exactly that bright ‘ring of fire’ around the black hole arises. And also unknown is what exactly happens when an object falls into a black hole.
The results of the research have been published in the Astrophysical Journal Letters.
Source: BBC

Video: Nature Video