Why a black hole picture is so important

News 11/04/2019

The world's first-ever image of a black hole conforms precisely to what scientists said it would. But if black holes swallow everything - even light - what are we actually looking at?

Turns out, it's a shadow.

This image shows us, if you will, the silhouette of a black hole

NASA senior research scientist Eric Christian told The AM Show on Thursday morning. "The dark spot in the centre of this donut is where the black hole blocks light."

The image was taken using a series of telescopes across the world, which together are known as the Event Horizon Telescope (EHT). In 2017 they were pointed at Messier 87, a supergiant elliptical galaxy 55 million light years away, with the terabytes of data culminating in Thursday's papers in scientific journal Astrophysical Journal Letters.

"Years ago, we thought we would have to build a very large space telescope to image a black hole," said Paul Hertz, director of astrophysics at NASA. "By getting radio telescopes around the world to work in concert like one instrument, the EHT team achieved this, decades ahead of time."

Photo credit: Getty/National Science Foundation

"It feels like looking at the gates of hell," Heino Falcke of Radboud University in Nijmegen said at a press conference announcing the findings. This is the end of space and time."

Previous photographs of the galaxy had shown massive beams of plasma emanating from the supermassive black hole at its core, firing across intergalactic space, but not the black hole itself. The new images show not just the black hole at the centre of  Messier 87, but the jet firing right across the galaxy.

"The fact there is a hole there says all that we thought about black holes is correct," said Dr Christian. "We're actually seeing this enormous black hole that's really far away, but tiny."

It's like imaging a dime on the moon.

Scientists at the Massachusetts Institute of Technology who took part in the research compared it to reading a text on a phone in New York from a sidewalk café in Paris or seeing a grapefruit on the moon.

 

EHT locations. Photo credit: Astrophysical Journal Letters

So why didn't they photograph the supermassive black hole at the centre of our own galaxy, the Milky Way?

"This black hole is really large," said Dr Christian. "They also looked at the black hole at the centre of our own galaxy, but there's a lot of gas between us and that black hole."

This black hole was just really large and relatively close on the scale of galaxies.

Despite both being categorised as supermassive, the black hole in Messier 87 is actually more than 1000 times bigger than our own.

And the orange stuff around it? That's superheated gaseous emissions. Parts of it are brighter because they're being "whipped toward Earth" by the hole's gravity, according to Science magazine, the colour changing much like a sound rises in pitch as it approaches you.

"In the optical range, the ring around the black hole would likely appear white, perhaps tinged with blue or red. "I'd expect it to be more of a whitish glow that is brighter along the crescent, dimmer at the other points, and then black where the black hole is casting its shadow."

While black holes themselves are invisible, they contain more matter than any other single object else in the universe Dr Christian explained.

But what form it takes, it's something that's beyond our mathematics

"The density, the compression in there, we can't get in to measure it because nothing gets out of there. But what originally fell into the black hole was just hydrogen, helium, all the stuff that makes up the universe… just gets pulled into this black hole. It's still in there, but basically all you've got is a massive object that completely warps the space around it."

That warping was predicted by Albert Einstein's General Theory of Relativity a century ago, which has passed its latest test with flying colours, scientists say.

"I don't think anyone should be surprised when yet another test of general relativity passes,"  Erin Bonning, astrophysicist at Emory University, told Live Science. "If they had walked on stage and said that general relativity had broken, I would have fallen off my chair."

Next scientists will be looking at our own black hole at the center of the Milky Way galaxy.

The AM Show / Newshub reporter Dan Satherly