Black Hole Close-Up

More than a century ago, physicists made the first calculations hinting at the existence of one of our universe’s most bizarre oddities. The math suggested that space contains black holes—objects so massive and dense that nothing can escape after falling in.

Black holes remained mainly theoretical curiosities until the 1960s, when astronomers started to detect activity in space that could be best explained by the presence of these giant objects. Since then, researchers have continued to learn about black holes indirectly, by studying their effects on nearby stars and other matter. Scientists think smaller black holes form in the explosions of dying stars. The origins of the largest ones, called supermassive black holes, are still unknown. But they all share one unusual feature: The pull of their gravity—a force that attracts objects toward one another—is so strong, even light can’t escape.

Black holes are some of the biggest mysteries in the universe. Physicists first described them more than a century ago. Their calculations suggested that space contains massive objects that pull in things around them. But back then, no one had solid evidence that black holes actually exist.

That changed in the 1960s. Astronomers started to detect strange activity when they looked at stars and other matter in space. The best explanation was that black holes were nearby. Since then, scientists have learned about black holes by studying their effects on other things.

Black holes come in different sizes. Scientists think the smaller ones form when dying stars explode. The largest ones are called supermassive black holes. No one knows how these form. But all black holes have something in common. The pull of their gravity—a force that attracts objects toward one another—is so strong, even light can’t escape.

Scientists spent nearly two years analyzing the observations from all eight telescopes and combining them into a single image. That unprecedented first portrait shows an irregular ring of light. At its center lies a dark shadow: the black hole’s event horizon. “There’s just something beautiful about that shadow,” says astrophysicist Daryl Haggard of McGill University in Canada. “Once you see it, you don’t forget it. People had predicted it might be possible to delve right down to the event horizon, but it was incredible to see it actually happen,” she says.

The shadow in the image relates to the black hole’s mass, which is the amount of matter it contains. More-massive black holes have bigger shadows. By measuring the silhouette, astrophysicists were able to make the most direct estimate yet of this black hole’s mass: about 6.5 billion times that of our sun.

Scientists spent nearly two years analyzing the data from the EHT. They combined observations from all eight telescopes into a single image. The result is the first-ever portrait of a black hole. It shows a ring of light with a dark shadow in the middle. The shadow is the black hole’s event horizon. “There’s just something beautiful about that shadow,” says Daryl Haggard. She’s an astrophysicist at McGill University in Canada. “Once you see it, you don’t forget it.”

The size of the shadow is also important. It tells scientists the black hole’s mass, or the amount of matter it contains. Astrophysicists measured the shadow in the EHT image. They calculated that the black hole is about 6.5 billion times as massive as our sun!

Since that first success, astronomers have been refining their technique and imaging more black holes. In May, they released an image of the supermassive black hole at the center of our own Milky Way Galaxy. Like the image of M87, this new one shows the black hole’s doughnut-shaped ring of light around the event horizon.

Astrophysicists hope their black hole photos will help them learn how these strange objects form, behave, and expand. The images will also allow scientists to check how their current understanding of gravity, magnetic fields, and matter holds up against one of the most extreme situations in our universe.

“The conditions near black holes are beyond anything we can create in a lab,” says Haggard. “Observing them is a great way to test our theories.”   

Capturing the M87 black hole was a huge success. Since then, astronomers have been improving their technique. They’ve also been observing more black holes. In May, they released an image of the black hole at the center of our galaxy, the Milky Way.

Astrophysicists hope their black hole photos will help them learn more about these strange objects. The images will also help them understand the physics of extreme situations in space.

“The conditions near black holes are beyond anything we can create in a lab,” says Haggard. “Observing them is a great way to test our theories.”