At 9 a.m. Eastern time on Wednesday, a group of astronomers who run a globe-girdling network of radio telescopes called the Event Horizon Telescope are expected to unveil the first-ever images of a black hole.
For some years now, scientific literature, news media and films have featured remarkably sophisticated and academic computer simulations of black holes. If all has gone well, the images today will reveal the real thing, and scientists at last will catch a glimpse of what had seemed unseeable.
How can I watch the big reveal?
A number of news conferences are being held around the world. You can watch one news conference on the National Science Foundation’s website, or in the video player embedded below.
Remind me, what’s a black hole?
Black holes are objects so dense that nothing, not even light, can escape from their gravity. They were predicted by the equations of Albert Einstein’s theory of general relativity, as solved by the German physicist Karl Schwarzschild in 1915. That theory ascribes gravity to the warping of space and time by matter and energy, much as a mattress sags under a sleeper.
To Einstein’s surprise, the equations indicated that when too much matter or energy was concentrated in one place, space-time could collapse, trapping matter and light in perpetuity. Einstein disliked that idea, but the consensus today is that the universe is speckled with black holes waiting for something to fall in. Many are the gravitational tombstones of stars that have burned up their fuel and collapsed. Others, millions or billions times more massive than the sun, lurk at the centers of galaxies.
Why do scientists want to take pictures of black holes?
Actual images would provide a final, ringing affirmation of an idea so disturbing that even Einstein, from whose equations black holes emerged, was loath to accept it.
Astrophysicists think that supermassive black holes are the engines that generate the prodigious energies of quasars and other explosive galactic nuclei. Doomed, superheated gas swirls around the hole, like water around a drain, and is forced out the sides as an enormous cosmic blowtorch. Today’s images could show how this process works.
Where are these black holes?
One of the objects the astronomers studied, known as Sagittarius A* (pronounced A-star) sits at the center of the Milky Way galaxy, buried in the depths of interstellar dust and gas. It is equivalent in mass to 4.1 million suns that otherwise have disappeared from the visible universe.
Another is in the center of Messier 87, a giant elliptical galaxy in the constellation Virgo that has a jet of energy some 5,000 light years long shooting out of it.
What will a black hole look like?
It might be circular, oval or some other shape entirely, depending on whether it is rotating, or if the Einsteinian equations describing it are slightly wrong, or if it is spitting flares of energy, which is how quasars produce fireworks visible across the universe.
How have scientists been trying to take the picture?
The images emerged from two years of computer analysis of observations from a network of radio antennas called the Event Horizon Telescope. In all, eight radio observatories on six mountains and four continents observed the Sagittarius and Virgo black holes on and off for 10 days in April of 2017.