Science & Technology

A Black Hole Was Photographed for the Very First Time

Eight telescopes working as a team accomplished a feat that astronomers have dreamed about for decades: They directly captured images of a black hole. What's equally incredible is how they got the image from so far away. This black hole is 55 million light-years from Earth — more than 11 times further away than the nearest star system — and is 6.5 billion times the mass of the sun.

Excitement Around the World

The scientific community was excited, with press releases coming from all over the world celebrating the accomplishment. It also generated six papers in a special issue of The Astrophysical Journal Letters, which means the astronomical community is taking the news very seriously.

The shadow of a black hole seen here is the closest we can come to an image of the black hole itself, a completely dark object from which light cannot escape. The black hole's boundary — the event horizon from which the EHT takes its name — is around 2.5 times smaller than the shadow it casts and measures just under 40 billion km across. While this may sound large, this ring is only about 40 microarcseconds across — equivalent to measuring the length of a credit card on the surface of the Moon.

The telescope set that cracked the black hole's code is called the Event Horizon Telescope (EHT), which includes eight radio telescopes all over the world. The telescopes work together through a process called interferometry, to get sharper images as a group than they would on their own. The full list of participating telescopes in EHT is eye-popping: It includes the Atacama Large Millimeter/submillimeter Array (ALMA), the Atacama Pathfinder Experiment, the IRAM (Institute of Millimeter Radioastronomy) 30-meter telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope Alfonso Serrano, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope.

"We are giving humanity its first view of a black hole – a one-way door out of our universe," said EHT project director Sheperd Doeleman of the Harvard-Smithsonian Center for Astrophysics in a press release from the Atacama Large Millimeter/submillimeter Array (ALMA). "This is a landmark in astronomy, an unprecedented scientific feat accomplished by a team of more than 200 researchers."

The researchers had images so sharp that they could even see the black hole's shadow. This effect takes place because the physics of a black hole is so very extreme. To find out more about why this shadow happened, you need to understand a little more about what black holes are and how they work.

Related Video: Here's What Scientists Predicted They'd See

What Is a Black Hole, Anyway?

You can think of black holes as supermassive objects in space — objects you don't want to get close to. That's because the gravitational field is so strong near these objects that nothing can escape, not even light (the fastest thing that moves in the universe). Black holes come in many sizes, ranging from comparable to the size of a star to massive behemoths that dominate the centers of galaxies.

This artist's impression depicts the black hole at the heart of the enormous elliptical galaxy Messier 87 (M87). This black hole was chosen as the object of paradigm-shifting observations by the Event Horizon Telescope. The superheated material surrounding the black hole is shown, as is the relativistic jet launched by M87's black hole.
In anticipation of the first image of a black hole, Jordy Davelaar and colleagues built a virtual reality simulation of one of these fascinating astrophysical objects. Their simulation shows a black hole surrounded by luminous matter. This matter disappears into the black hole in a vortex-like way, and the extreme conditions cause it to become a glowing plasma. The light emitted is then deflected and deformed by the powerful gravity of the black hole.
This image shows the locations of some of the telescopes making up the EHT, as well as the long baselines between the telescopes.

When it comes to smaller black holes, astronomers are pretty sure those happen after the collapse of a huge star near the end of its life when it has no fuel left to burn gases. The resulting collapsing gravitational field is so strong that the star vanishes into a point. This point is invisible to our eyes, although when black holes feed on nearby gas, we can see their activity using X-rays or gamma rays.

It's unclear how supermassive black holes form, although there are a lot of theories. Some suggest these happen after a gas cloud collapses. Others think they are black holes that started off small but grew larger as the hole ate gas and nearby objects over billions of years. This is part of what makes black holes so interesting — we don't know all their secrets.

So how about that shadow? Researchers suggest that if the black hole is embedded in a disc of glowing gas, the black hole will create a shadow. This happens because light is being bent at the event horizon: the edge of the black hole where objects cannot escape.

What we do know is that this direct image of a black hole was a momentous achievement for science. Here's to many more!

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Learn more about this momentous effort in "Einstein's Shadow: A Black Hole, a Band of Astronomers, and the Quest to See the Unseeable" by Seth Fletcher. The audiobook is free with an Audible trial. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Elizabeth Howell April 10, 2019

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