After a week of teasing, astronomers have finally released the first image of a black hole, as taken by the Event Horizon Telescope (EHT), a network of 8 radio telescopes around the world
The black hole, which weighs 6.5-billion times that of the Sun and resides some 55 million light-years from Earth, is at the center of Messier 87, a massive galaxy in the Virgo galaxy cluster.
“We have seen what we thought was unseeable. We have seen and taken a picture of a black hole,” said EHT Director and astrophysicist Sheperd Doeleman as reported by Science News:
That's because black holes are notoriously hard to see. Their gravity is so extreme that nothing, not even light, can escape across the boundary at a black hole's edge, known as the event horizon. But some black holes, especially supermassive ones dwelling in galaxies’ centers, stand out by voraciously accreting bright disks of gas and other material. The EHT image reveals the shadow of M87’s black hole on its accretion disk. Appearing as a fuzzy, asymmetrical ring, it unveils for the first time a dark abyss of one of the universe’s most mysterious objects.
But have you ever wondered who thought of the idea of black holes in the first place?
If you thought that black holes are a new concept in astrophysics, you'd be wrong: The idea of a star that's so dense that not even light could escape from its gravitational field was an old one - it was proposed in 1783 by an English clergyman named John Michell.
Michell wrote:
If there should really exist in nature any bodies, whose density is not less than that of the sun, and whose diameters are more than 500 times the diameter of the sun, since their light could not arrive at us; or if there should exist any other bodies of a somewhat smaller size, which are not naturally luminous; of the existence of bodies under either of these circumstances, we could have no information from sight; yet, if any other luminous bodies should happen to revolve about them we might still perhaps from the motions of these revolving bodies infer the existence of the central ones with some degree of probability, as this might afford a clue to some of the apparent irregularities of the revolving bodies, which would not be easily explicable on any other hypothesis; but as the consequences of such a supposition are very obvious, and the consideration of them somewhat beside my present purpose, I shall not prosecute them any further.
Michell called these objects, "dark stars."
Alas, Michell's idea of black holes didn't convince his contemporaries and it was forgotten (until his writings were re-discovered in the 1970s). Michell died in relative obscurity, and no image of him survived to this day.