Why a blurry picture of a black hole matters
The first actual picture of a black hole was released on Wednesday morning.
The picture is of a blurry, uneven golden ring around a black circle. Outside the ring, the light dies off again into darkness.
It may not seem like much, but it depicts the black hole M87, which is over 54-million light years away, at the centre of a neighbouring galaxy.
It’s six-billion times the mass of our sun, and as big as our entire solar system.
The picture — taken over a period of time two years ago by the Event Horizon Telescope (EHT) project — is being hailed as a breakthrough, because black holes by definition don’t allow for light to escape.
“We’re seeing the unseeable,” U.S. National Science Foundation director France Córdova said at one of the simultaneous press conferences held around the world.
“This is a huge day in astrophysics.”
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But the picture may seem underwhelming to some. Artist’s renderings or simulations of black holes in the past have looked very similar.
The Event Horizon Telescope captured the first picture of a black hole. The picture was released on April 10, 2019.Handout / National Science Foundation
So why does having this new picture matter? Here’s what you need to know about the image:
What is in the picture?
A black hole is a dense celestial entity. It sucks in matter and light and doesn’t allow them to escape.
Supermassive black holes reside at the centre of most spherical galaxies – like our own Milky Way. While smaller black holes are formed by collapsed stars, we don’t yet know what makes a supermassive black hole.
Much of the matter around a black hole gets sucked into the vortex, never to be seen again, but the new picture captures gas and dust that are lucky to be circling just far enough to be safe.
The picture shows a ring of light around a region of darkness. The light — hot disrupted matter and radiation — is circling at tremendous speed at the event horizon, or the edge, of a region of darkness representing the actual black hole. This is known as the black hole’s shadow or silhouette.
The measurements are taken at a wavelength the human eye cannot see, so the astronomers added colour to the image.
They chose “exquisite gold because this light is so hot,” Jessica Dempsey, a co-discoverer and deputy director of the East Asian Observatory in Hawaii, told the Associated Press.
Other images show different wavelengths, and show other properties of the black hole. This includes the clouds of particles streaming away from the black hole in two opposing jet streams.
The way the light appears in the picture shows researchers how gravity works at its most extreme manifestation.
It’s close to the predicted image
Simulations of black holes over the years have used Einstein’s theory of general relativity to predict how a black hole looks and how it acts.
(The general relativity theory has to do with gravitational fields and other forces of nature – and much of modern astrophysics, like the study of black holes, is based on it.)
CONCEPT IMAGE: A supermassive black hole with millions to billions times the mass of our sun is seen in an undated NASA artist’s concept illustration.REUTERS/NASA/JPL-Caltech/Handout/File Photo
The scientists said Einstein’s theory predicted the shape of the shadow would be almost a perfect circle — as it turned out to be.
“You know we can’t test general relativity in a lab. We can’t make a black hole. We can’t do experiments where we crash planets together and see what happens,” Pauline Barmby, professor of physics and astronomy at Western University, told Global News.
The fact that the picture is so similar to the prediction is a win, experts say.
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It “increases our confidence in this century-old theory,” astrophysicist Dimitrios Psaltis of the University of Arizona told Reuters.
But there’s more to astrophysics than relativity.
“We know it can’t be the ‘final answer’ — there are things that relativity doesn’t explain,” Barmby cautioned. “We hope these tests will eventually show us disagreement with predictions and thus the way to an improved theory.”
And to researchers around the globe, having the picture means much more than just looking at a pretty image.
“Pictures from computer simulations can be very pretty, but there’s literally nothing like a picture of the real universe, however fuzzy and monochromatic,” Johns Hopkins astrophysicist Ethan Vishniac told the Associated Press.
Why does it matter?
The picture has a lot to tell you about how black holes interact with the galaxies around them – which will contribute to a greater understanding of the universe.
“It’s important because it’s a big part of the universe around us,” Barmby said.
“Although that’s not always obvious in our everyday life, the universe and its properties have a lot to do with how we ended up here.
“If we really want to go all the way back and figure out why we’re here — not just why we’re in Ontario — but you know why our planet is here, why we’re here at all, understanding that big picture is part of that.”
“Imaging a black hole is just the beginning of our effort to develop new tools that will enable us to interpret the massively complex data that nature gives us,” Psaltis added.
Real world effects of relativity and the picture
While knowing what a black hole’s silhouette looks like isn’t going to help us make a time machine, there are real-world applications of Einstein’s theory of general and special relativity.
Einstein’s theory of general relativity speaks to the relationship between gravity and other forces of nature — for example, it predicted how clocks run slower depending on how close to a gravitational well (e.g. a planet like Earth) it is.
“We do use Einstein’s theory of relativity for things related to the Earth,” Barmby said. “For example, the fact that GPS satellites are in orbit around the Earth and not on the Earth means that time runs a little bit differently for them.”
But other real-world applications could come from the research used to capture the image. A network of satellites and radio telescopes were networked to be able to image the black hole – using techniques similar to MRI machines.
“There’s some transferability of that kind of information and those kinds of skills — not necessarily that we can build mini black holes.”
*with files from Reuters and the Associated Press