HOW DOES A BLACK HOLE WORK?
In many ways, a black hole resembles a bathtub drain: The closer light or matter gets to the center, the faster it moves on its way to final disappearance. But while gravity remains constant in a bathtub, it is relentlessly increasing in a black hole. The gravitational force becomes so powerful that it can even bend rays of light. The illustration shown here depicts a black hole revolving around a vertical axis, with the poles at the top and bottom. The photo on the first page, however, provides a kind of bird’s eye view. Nearest to the black hole, the gravitational light-bending is so intense that the underside of the disk is visible as a bright ring of light around the black hole.
h my gosh—there is it! We’ve got it! This is the triumphant sentiment that surged in the mind of astrophysicist Silke Britzen when she first saw the incredible photo. “It was exactly what we’d been looking for the whole time: the first image of a black hole.”
CAN SOMETHING BE REMOVED FROM THE UNIVERSE?
Until that moment, black holes had only existed in theory. Theoretically a black hole is a star that’s many times the size of our Sun and has reached the end of its life. After burning the last of its fuel, the star is thought to collapse and fall in on itself. When formed by the collapse of a single star, a black hole is relatively small but infinitely dense. Its unimaginably strong gravitational force pulls in all the matter and energy that lies within a boundary called the event horizon. “Every ray of light, every photon that gets close to the black hole actually bends toward the black hole and then becomes entirely removed from the universe as we know it,” says Dimitrios Psaltis, a professor of astronomy and physics at the University of Arizona.
What goes on in a black hole not only pushes the limits of the imagination but also those of the known laws of physics. Thus it’s not surprising that some scientists doubted their very existence—at least until recently…
HOW DO YOU LISTEN TO SPACE?
A decade ago, 200 scientists from 59 institutions and 18 countries gathered to clear up this cosmic mystery once and for all. They were determined to take a photo of a black hole, but they faced a couple problems. Problem 1: A black hole lets no light escape and is thus invisible; black holes are black because they suck up all of the light around them. There’s actually a black hole at the center of our own galaxy, the Milky Way, but it is shrouded by a fog of charged particles that would make any image hazy. A much better subject for study lies at the center of a neighboring supergiant elliptical galaxy called Messier 87. But M87, in turn, poses problem 2: While close enough to be considered a neighbor, the galaxy is around 55 million lightyears away in the constellation Virgo. And despite its substantial size, the enormous distance from Earth makes it appear tiny, although it is actually large enough to be observed with a small telescope. Astrophysicist Heino Falcke, who had the original idea for the Event Horizon Telescope project, has said it’s like standing in Brussels and focusing on a mustard seed in Washington, D.C.
These problems were ultimately solved by a telescope with a mirror as large as the surface of the Earth. This virtual telescope is 5,000 miles wide and was created by networking eight radio telescopes located on four continents. The linking procedure is conducted only once per year when the Earth is perfectly aligned with the target. The sky must be crystal-clear at all eight of the locations, and the telescopes have to be synchronized to within one-trillionth of one second. That’s the only way the Event Horizon Telescope can work, and even under ideal conditions scientists would love to get it to work even better. The only remaining problem is that a large part of the virtual telescope is essentially blind because of a lack of data from areas of Earth’s surface where there aren’t any networked observatories. Therefore the missing data must be reconstructed by utilizing algorithms that only the fastest supercomputers on the planet can handle.
FILMING THE GATES OF HELL
The target black hole in the Messier 87 galaxy has a mass 6.5 billion times that of our Sun and constitutes one of the greatest concentrations of energy in our corner of the universe. To get a snapshot of this behemoth, the algorithms had to contend with 4,000 terabytes of data stored on
hard drives that were flown from the various observatories to one central location. And that takes time: The data from Antarctica can be delayed by as much as six months in winter when the airfields are closed.
To guarantee a processing error wouldn’t result in a false declaration of success, four international teams competed with one another over a period of months to analyze the raw data utilizing a number of different methods. In this case they all came to the same conclusion: They were indeed beholding an image from a part of the universe no human had ever laid eyes on before. “We have seen the gates of hell at the end of space and time,” says Heino Falcke. And according to his colleague Silke Britzen, “We can finally say that, yes, black holes do exist, and they look the way we expected—they could, after all, have been quite different.” And not only that: The size and shape are in keeping with Einstein’s theory.
So what’s next? The Event Horizon Telescope collaborators are already planning phase 2: a video recording. Now that their networked tool has proved that a photo is obtainable, they want to get a moving image of the gravitational monster. And they plan to use their equipment on other black holes as well. How will they do it? By building an observatory even bigger than Earth: “By adding space telescopes to the Event Horizon array, we can see even smaller black holes that are closer to our solar system,” explains Professor Dimitrios Psaltis.
“Then we can do similar experiments with perhaps 10, 20, or 30 black holes in the nearby universe.”
The next phase of the project is set for March 2021 and will involve some 350 scientists and 60 institutions from 20 countries and regions. It will link 11 telescopes: one each in Antarctica, France, Greenland, Mexico, and Spain as well as two each in Arizona, Chile, and Hawaii. Future plans include the addition of a telescope on the Moon. Michael D. Johnson of the Harvardsmithsonian Center for Astrophysics is optimistic: “Then we would really be looking at entirely new science.”
“IT IS A RING OF FIRE CREATED BY THE DEFORMATION OF SPACE-TIME: THE GATES OF HELL AT THE END OF SPACE AND TIME.”