What the quest to photograph black holes can tell us about our universe

What the quest to photograph black holes can tell us about our universe

Hours after revealing the first image of the black hole at the center of the Milky Way, scientists from the Harvard and Smithsonian team discussed its significance in an online panel. Credit: Chris Snape/Harvard Photographer

Not so long ago, the idea of ​​photographing a black hole was as fanciful as photographing a rhinoceros. Now, scientists have not one but two images of two different supermassive black holes – and both look magically like smoldering cakes.

“I remember when black holes were purely theoretical,” Eileen Stofan, the undersecretary for science and research at the Smithsonian Institution and a former chief scientist at NASA, said during a hearing after Thursday’s revelations. The conversation, moderated by Stofan, brought together four members of the Harvard-led team of scientists that revealed to the world in 2019 the first image of a black hole — a giant named M87 after its galaxy Messier 87. Hours before the panel, the team shared a second image — Close-up of Sagittarius A-star (or Sgr A*), a black hole feeding on light and cosmic debris at the center of our Milky Way.

“There is no doubt now that we have seen black holes for the first time,” said Shep Doelman, founding director of the Event Horizon Telescope, an international team of more than 100 scientists led by the Center for Astrophysics. Harvard and Smithsonian. “It is the dawn of a new era in astronomy.”

In this new age, scientists can prove – or disprove – Einstein’s well-established theories of gravity and relativity, find Earth 2.0, or discover a wormhole of another universe. (The latter wouldn’t be too difficult for Doeleman, who, rudely, said he came from another world.)

Photographing a black hole is more difficult than it seems. To take pictures of very distant objects, “you’d need an Earth-sized telescope,” said Carrie Howworth, an engineer and chief technology officer at the Astrophysics Center. “We didn’t do it because that’s impossible, and it’s going to spoil a lot of people’s opinions,” she said.

Instead, researchers have turned Earth into a giant telescope by coordinating individual instruments located in Hawaii, Chile, Mexico, Spain, France, and elsewhere. Each team had to take a photo at the exact same time. Because black holes gobble up everything that is too close – even light – to be seen. But its massive gravity pulls on and compresses nearby light and debris, creating a spinning gas vortex teeming with energy. “Transforming falling matter into luster,” Doleman coined it.

This luminescence can be seen and photographed. Some of the light pulled into the black hole’s gravitational field makes a U-shaped spin or loop before escaping and shooting toward Earth, bearing an image of where it came from. The EHT team’s final image is a set of images taken by each telescope and stacked one on top of each other. To combine all that data — light data, captured in a very precise moment — the team had to achieve another strange feat. Each telescope team froze their light, stored it on hard disks (too bulky to send over the Internet), and flew it to one central location.

M87, the first black hole to get the star treatment, is about 1,000 times larger than Sagittarius A and more stable, but the images came out roughly the same, an inversion of the EHT — and Albert Einstein. Einstein assumed that black holes have only three properties – mass, rotation and charge – and no “hair” (as astrophysicists like to name additional properties). The only difference is a slight blur in the image of the star Sagittarius. Our galaxy’s black hole is much noisier, like a small child, said astrophysicist Paul Ted, and it’s hard to take a clean picture of something that’s constantly changing. Plus, there’s some cosmic soup between us and the Sagittarius A-star, which slightly obscures the images. “Even with this,” Ted said, “I’m still amazed at how similar these photos are.”

By the way black holes are described, you might expect them to be insatiable monsters, sucking up everything in space like a bathtub drain. not exactly. While they’re the most powerful objects in the universe — a black hole formed by folding the Earth in half could occupy Manhattan for a year — Doleman said they don’t gobble up entire galaxies, only distorting spacetime and displacing objects from their intended paths.

This is good news because the EHT team suspects that there is a supermassive black hole at the center of each galaxy. But even with these new photos, Ted said, “we hardly know anything about it.” (When asked why black holes are cake-shaped, he replied, “Because they are delicious.”)

“Black holes live within the limits of our current knowledge of physics and astrophysics,” said Angelo Ricciarti, who brought a pet black hole called Po – a smooth black quarry with googly eyes – to the panel. These new images help Ricarti and other scientists study the strange physics of the super-hot gas orbiting black holes, as well as how the two giants shoot jets of this gas a million light-years away in any direction. These jets could help explain “our cosmic origin story,” Riccarte said, have profound implications for how our galaxy evolved, or connect theories of the very big to the very small to support a theory of everything. “There are a lot of things we still don’t fully understand in this harsh environment,” he said.

To get a better understanding, Doeleman wants to build a larger telescope by placing another imaging device on an Earth-orbiting satellite. He also hopes to capture something more exciting than a picture of a black hole: a film of a black hole.

“If we could time the matter’s orbits, it would be a very different test of Einstein’s theory,” he said.

Capturing a Black Hole: How the EHT Super Telescope Works

Presented by Harvard University

This story was published with permission from The Harvard Gazette, the official journal of Harvard University. For more university news, visit Harvard.edu.

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