The first image of a black hole has been revealed by scientists

Wednesday, 10 April 2019

Scientists have revealed the first image ever made of a black hole, depicting its hot, shadowy edges where light bends around itself in a cosmic funhouse effect.

Assembling data gathered by eight radio telescopes around the world, astronomers created the picture showing the violent neighbourhood around a supermassive black hole, the light-sucking monsters of the universe theorised by Albert Einstein more than a century ago and confirmed by observations for decades.

It looked like a flaming orange, yellow and black ring.

The image of the black hole was revealed during a live-streamed press conference.

'We have seen what we thought was unseeable. We have seen and taken a picture of a black hole. Here it is,' said Sheperd Doeleman of Harvard. Jessica Dempsey, a co-discoverer and deputy director of the East Asian Observatory in Hawaii, said that when she first saw the image, taken two years ago, it reminded her of the powerful flaming Eye of Sauron from the Lord of the Rings trilogy.

* Here's what two black holes smashing into each other sounds like

* Roger Hanson: Stepping aside for Stephen Hawking**

The Event Horizon Telescope is a network of 10 radio telescopes on four continents that collectively operate like a single instrument nearly the size of the Earth. The scientists behind this mega-telescope boast that their ability to resolve objects in deep space is equivalent to being able to count the dimples on a golf ball in Los Angeles while standing in New York City.

Unlike smaller black holes that come from collapsed stars, supermassive black holes are mysterious in origin. Situated at the centre of most galaxies, including ours, they are so dense that nothing, not even light, can escape their gravitational pull. This one's 'event horizon' - the point of no return around it, where light and matter begin to fall inexorably into the abyss - is as big as our entire solar system.

Three years ago, scientists using an extraordinarily sensitive observing system heard the sound of two much smaller black holes merging to create a gravitational wave, as Albert Einstein predicted. The new image, published in the Astrophysical Journal Letters and announced around the world in several news conferences, adds light to that sound.

The live streamed press conference was watched around the world.

Outside scientists suggested the achievement could be worthy of a Nobel Prize, just like the gravitational wave discovery.

While much around a black hole falls into a death spiral and is never to be seen again, the new image captures 'lucky gas and dust' circling at just far enough to be safe and seen millions of years later on Earth, Dempsey said.

Taken over four days when astronomers had 'to have the perfect weather all across the world and literally all the stars had to align,' the image helps confirm Einstein's general relativity theory, Dempsey said. Einstein a century ago even predicted the symmetrical shape that scientists just found, she said.

'It's circular, but on one side the light is brighter,' Dempsey said. That's because that light is approaching Earth.

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,' Dempsey said. 'Making it these warm gold and oranges makes sense.'

What the image shows is gas heated to millions of degrees by the friction of ever-stronger gravity, scientists said. And that gravity creates a funhouse effect where you see light from both behind the black hole and behind you as the light curves and circles around the black hole itself, said astronomer Avi Loeb, director of the Black Hole Initiative at Harvard. (The lead scientists in the discovery are from Harvard, but Loeb was not involved.)

The project cost $US50 million to $US60 million, with $US26 million of that coming from the National Science Foundation.

Johns Hopkins astrophysicist Ethan Vishniac, who was not part of the discovery team but edits the journal where the research was published, pronounced the image 'an amazing technical achievement' that 'gives us a glimpse of gravity in its most extreme manifestation.'

He added: 'Pictures from computer simulations can be very pretty, but there's literally nothing like a picture of the real universe, however fuzzy and monochromatic.'

'It's just seriously cool,' said John Kormendy, a University of Texas astronomer who wasn't part of the discovery team. 'To see the stuff going down the tubes, so to speak, to see it firsthand. The mystique of black holes in the community is very substantial. That mystique is going to be made more real.'

There is a myth that says a black hole would rip you apart, but Loeb and Kormendy said the one pictured is so big, someone could fall into it and not be torn to pieces. But the person would never be seen from again.

Black holes are 'like the walls of a prison. Once you cross it, you will never be able to get out and you will never be able to communicate,' Loeb said.

The first image is of a black hole in a galaxy called M87 that is about 53 million light years from Earth. One light year is 5.9 trillion miles, or 9.5 trillion kilometres. This black hole is about 6 billion times the mass of our sun.

The telescope data was gathered by the Event Horizon Telescope two years ago, but it took so long to complete the image because it was a massive undertaking, involving about 200 scientists, supercomputers and hundreds of terabytes of data delivered worldwide by plane.

The team looked at two supermassive black holes, the M87 and the one at the centre of our own Milky Way galaxy. The one in our galaxy is closer but much smaller, so they both look the same size in the sky. But the more distant one was easier to take pictures of because it rotates more slowly.

'We've been hunting this for a long time,' Dempsey said. 'We've been getting closer and closer with better technology.'

WHAT IS A BLACK HOLE?

The astronomical image of a black hole represents a tremendous breakthrough for astrophysics and the culmination of a century of theoretical and observational labour. Even a generation or two ago, scientists weren't entirely confident that black holes existed, because even though they looked plausible mathematically the observational evidence was indirect.

Few people have hated the idea of black holes more than the man who helped establish their existence: Einstein. His celebrated general theory of relativity in 1915 described how matter can cause space and time - 'spacetime' - to curve, much the way a bowling ball will dimple the surface of a trampoline. Gravity is the effect of that warping of the geometry of the cosmos. Physicists put it this way: 'Matter tells space and time to curve. Space and time tell matter to move.'

Just months after Einstein's equations were published, a German scientist, Karl Schwarzschild, tweaked Einstein's equations and came up with a disconcerting conclusion. If an object was dense enough, he found, it would eventually punch through the universe's fabric, creating a bottomless pit in spacetime known as a 'singularity.'

Even a generation or two ago, scientists weren't entirely confident that black holes existed.

These singularities - named 'black holes' in the 1960s - are gravity wells so strong that, once you enter, you can't turn back. The gravitational field of a black hole is so intense that not even light can escape the 'event horizon', the point of no return.

Einstein found the notion of a singularity so preposterous that he devoted an entire research paper to debunking it. But as time went on, more and more researchers found more clues that Schwarzschild's wild idea might be real.

The astrophysicist Subrahmanyan Chandrasekhar, an expert on stellar evolution, explained that some stars would collapse catastrophically after they died. Then physicists J Robert Oppenheimer and Hartland Snyder showed how that collapse could continue until it formed the kind of singularity Schwarzschild had written about.

But stellar-mass black holes, the kind that form from collapsed stars, are not the only black holes in the universe.

In the 1960s and '70s, scientists proposed that some mysteriously bright objects they'd been calling quasars might actually be clouds of swirling, superheated material surrounding black holes hundreds of thousands of times more massive than the sun. As these 'supermassive' black holes slurp up gas and stardust, the theory goes, matter outside the event horizon speeds up, and some of it is flung back into the outer reaches of galaxies. X-rays and radio waves accompany these jets of ultrahot gas. Paradoxically, all this activity makes the black holes some of the brightest things in the universe - and obscures the darkness at their cores.

In 1974, researchers at the Green Bank Radio Telescope in West Virginia captured the powerful radio signal from the core of the Milky Way. This was the first observational evidence for the existence of Sagittarius A*, the black hole around which our entire galaxy spins.

Now astrophysicists believe that supermassive black holes lurk in the hearts of all large galaxies. One of the big unknowns is the chicken-and-egg question of what came first - the black hole or the galaxy?

Few people have hated the idea of black holes more than the man who helped establish their existence: Albert Einstein.

In case you're wondering, black holes are not among the many things that humans should be worried about. They aren't rogue entities on the prowl, looking to devour nice planets. They're not cosmic vacuum cleaners. Still, you wouldn't want to cross the event horizon. That would go badly.

Eventually you would reach the 'singularity.' That's where, according the physics equations, the curvature of spacetime becomes infinite and all known laws of physics cease to apply. 'At that point, nobody knows what the hell to say about it,' Weiss said.

To understand the singularity, Weiss said, 'you need to know how to do the quantum theory of gravity.'

Which is? 'We don't have a theory that is the quantum theory of gravity,' he said.

Science writers often describe black holes as 'monstrous,' but they don't really have much personality at all. Indeed, anything that plunges into a black hole is eventually stripped of all identity other than mass, charge and spin. Protons, neutrons, electrons, big metallic atoms, whatever goes in becomes undifferentiated as it reaches the 'singularity' at the centre of the black hole.

The physicist John Wheeler famously declared that black holes 'have no hair,' meaning no hairstyle, nothing personal and flashy. The physicist Brian Greene, in his book The Elegant Universe, notes that this featurelessness of black holes makes them oddly similar to subatomic particles, leading to 'the strange speculation that black holes might actually be gigantic elementary particles'.

As for what a 'singularity' is, no one really knows. You probably can't describe it with spatial co-ordinates, and neither is there such thing as time in a singularity. In a sense, there's no there there. And nothing really happens.

'It is one of the great mysteries in science right now - what is a black hole?' said Chiara Mingarelli, an astrophysicist at the Flatiron Institute Center for Computational Astrophysics in New York. 'What is the singularity? Mathematically we define it as the infinite curvature of spacetime. But that can't possibly be true.'

She means that the mathematics may not correspond to the actual reality at the heart of the black hole.

'Mathematically that's the best we can do. And that's fine and that's fair. But if we could actually observe what's at the centre of a black hole, a singularity, it's likely a thing,' she said.

The famed LIGO experiment - the Laser Interferometer Gravitational-wave Observatory - has successfully picked up the signature, in the form of gravitational waves, of solar-mass black holes merging. In the first detection, the two black holes were estimated at roughly 30 solar masses each. When they merged, about three solar masses of energy dissipated across the universe in the form of the gravitational waves, which LIGO detected.

- AP, Washington Post