3 huge questions that the black hole Image did not answer

An international network of radio telescopes has produced the very first close-up image of the shadow of a black hole, revealed by scientists this morning (April 10). This collaboration, called Event Horizon Telescope, has confirmed decades of predictions about the behavior of light around these dark objects and ushered in a new era of black hole astronomy.

"From a scale of zero to incredible, it was incredible," said Erin Bonning, an astrophysicist and black hole researcher at Emory University, who did not participate in the event. 39, imaging effort.

"That said, that's what I expected," she told Live Science.

The announcement, teased for about a week and a half in advance, has managed to be both incredibly exciting and almost completely devoid of surprising details or new physics. The physics did not collapse. No unexpected features of the black holes have been revealed. The image itself was almost perfect for illustrating the black holes that we usually see in science and pop culture. The big difference is that it's a lot more blurry. [9 Weird Facts About Black Holes]

Many important black hole issues remain unresolved, Bonning said.

How do black holes produce their huge jets of hot, fast material?

(Image: © Credit: X-rays: NASA / CXC / Villanova University / J. Neilsen, Radio: Collaboration with Event Horizon Telescope)

All supermassive black holes have the ability to chew material nearby, absorb most of it beyond their event horizons, and spit the rest into space at a speed close to light in flamboyant towers called "relativistic jets" by astrophysicists.

And the black hole in the center of Virgo A (also called Messier 87) is renowned for its impressive jets, material and radiation throughout the space. His relativistic jets are so huge that they can escape the surrounding galaxy.

(Image: © J. Biretta et al., Hubble Heritage Team (STScI / AURA), NASA)

And physicists know the big picture of how this happens: the material speeds up at extreme speeds when it falls into the gravity of the black hole, and then a part escapes by keeping that inertia. But scientists disagree on the details of how this happens. This image and the associated papers do not offer details yet.

Bonning explained that to solve this problem, it would be necessary to link the observations of the Event Horizons telescope – which cover a relatively small space – to much larger images of relativistic jets.

Physicists do not have answers yet, she said, but there is a good chance that they will arrive soon, especially when the collaboration will produce images of her second target: the supermassive black hole. Sagittarius A * in the center of our own galaxy, does not produce jets like Virgo A's. Comparing the two images, she said, could offer some clarity.

How does general relativity and quantum mechanics come together?

Whenever physicists come together to talk about a truly exciting new discovery, you can expect to hear someone suggesting that it might help explain "quantum gravity".

Indeed, quantum gravity is the great unknown of physics. For about a century, physicists have used two different sets of rules: general relativity, which covers very big things like gravity, and quantum mechanics, which covers very small things. The problem is that these two rules contradict each other directly. Quantum mechanics can not explain gravity and relativity can not explain quantum behavior.

One day, physicists hope to connect the two in a unified theory, probably involving a kind of quantum gravity.

And before the announcement today, there was speculation that this could include a breakthrough on the subject. (If predictions of general relativity had not been corroborated in the image, it would have advanced the balloon.) At a press briefing from the National Science Foundation, Avery Broderick, physicist at the University of Waterloo in Canada, collaborator on the project, suggested what kind of responses might be forthcoming.

But Bonning was skeptical of this claim. This image was not at all surprising from a general relativity point of view, so she offered no new physics to bridge the gap between the two areas, Bonning said.

Still, it's not crazy that people hope to get answers from this type of observation, she says, because the edge of the shadow of a black hole brings relativistic forces into tiny and quantum spaces.

"We expected to see quantum gravity very, very close to the horizon of events or very, very early in the early universe [when everything was packed into a tiny space]," she says.

But with the still fuzzy resolution of the Event Horizons telescope, she said, we probably will not find that kind of effect, even with future planned upgrades.

Was Stephen Hawking's theories as correct as those of Einstein?

The greatest contribution of physicist Stephen Hawking at the beginning of his career was the idea of ​​"Hawking radiation", namely that black holes are not actually black, but that they emit small amounts of radiation over time. The result was extremely important because it was shown that once a black hole ceases to grow, it starts to contract very slowly because of the loss of energy.

But the Event Horizons telescope has not confirmed or denied this theory, said Bonning, without anyone expecting it.

Giant black holes like Virgo A, she says, emit very little Hawking radiation in relation to their total size. While our most advanced instruments can now detect the bright lights of their event horizons, they are unlikely to master the ultra-dark glow of the surface of a supermassive black hole.

These results, she said, will probably come from smaller black holes – theoretical and ephemeral objects so small that you could lock all their event horizon into your hand. With the ability to observe closely, and many more available radiation relative to their overall size, humans could possibly determine how to produce or find one and detect radiation.

So what did we learn from this picture?

First, physicists have learned that Einstein was right, again. The perimeter of the shadow, out of sight of the Event Horizons telescope, forms a perfect circle, just like twentieth-century physicists who were working with Einstein's equations of general relativity.

"I do not think anyone should be surprised when a new test of general relativity is successful," Bonning said. "If they had walked on the stage and declared that the general relativity was broken, I would have fallen off my chair."

The result, with more immediate practical implications, she said, is that the image allowed scientists to accurately measure the mass of this supermassive black hole, located at 55 million years old. light at the heart of the Virgin galaxy A. It is 6.5 billion times more massive than our sun.

That's a big problem, said Bonning, as it could change the way physicists weigh supermassive black holes in the heart of more distant or smaller galaxies.

Right now, physicists measure the mass of the supermassive black hole in the heart of the Milky Way quite accurately, says Bonning, because they can see how gravity moves individual stars around it.

Hello. Here is a group of stars orbiting the central black hole of the Milky Way over a period of about 20 years. The star near the center passes less than 20 billion km from the bh and reaches a speed of about 3% of the speed of light. Image: ESO / MPE (doi: 10.1038 / d41586-018-05825-3) pic.twitter.com/bA7WWu6TeNMarch 28, 2019

But in other galaxies, our telescopes can not see the movements of individual stars, she said. Physicists are therefore confronted with more approximate measurements: how the mass of the black hole influences the light coming from different layers of stars of the galaxy, or how its mass influences the light coming from different layers of gas floating freely in the galaxy.

But these calculations are imperfect, she said.

"You have to model a very complex system," she said.

And both methods end up producing somewhat different results in all the physicists in the galaxy observed. But at least for the black hole of the Virgin A, we now know that a method is correct.

"Our determination of 6.5 billion solar masses ends up landing just after the determination of the heavier mass of [the light coming from stars]"Said Sera Markoff, an astrophysicist from the University of Amsterdam and project collaborator, during the briefing.

This does not mean that physicists will simply adopt this approach to measure black hole masses, Bonning said. But it offers an important data point for refining future calculations.

Originally published on Science live.