'We've now seen the unseeable': Black hole photographed for the first time Social Sharing

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Nicole Mortillaro · CBC News · Posted: Apr 10, 2019 9:10 AM ET | Last Updated: 28 minutes ago

1st-image-of-black-hole.jpg
This is the first image ever taken of the event horizon of a supermassive black hole, captured by the Event Horizon Telescope in 2017. (Event Horizon Telescope)
Black holes have been mysterious and elusive — until now. Astronomers using the Event Horizon Telescope (EHT) have, for the first time, photographed one.

"We've now seen the unseeable," said Avery Broderick, associate professor at the University of Waterloo's physics and astronomy department, who was part of the international EHT research team. "Black holes are made real — they're not just the scribblings on theorists' chalkboards anymore, but they really are out there in the night."

The image, which shows an orange ring around a round, black silhouette, is of the black hole at the centre of Messier 87 (M87), a galaxy 50 million light-years from Earth. This black hole is one of the most massive known: it's six billion times more massive than our sun.

Black holes are so dense and have such strong gravity that anything that crosses their threshold — known as the event horizon — gets pulled into them, never to return. That includes both matter and light, making them black and invisible — and therefore very difficult to see and photograph.

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1st photo of a black hole LIVE
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For the first time, scientists have captured an image of a black hole 0:00
An international team of more than 200 people spent more than a decade working to capture the image released today.

Black holes are made real — they're not just the scribblings on theorists' chalkboards anymore, but they really are out there in the night.- Avery Broderick , University of Waterloo associate professor
"Seeing the culmination of that effort was simply a marvelous moment," Broderick said. "But at the same time I'm very excited about the future because this marks the beginning of a new era in astronomy, a new era of research into gravity. And we really just are standing at the threshold today."

That's because the images allow scientists to test Einstein's general theory of relativity in ways that they never have before. On Earth, Newton's laws of physics and the way they describe gravity work pretty well. But when gravity becomes extreme, Newton's laws and general relativity predict very different things. That kind of extreme gravity doesn't exist in our solar system, but it does in black holes.

"We're able to probe general relativity in this region that has never been accessed before," Broderick said. "That's completely new and extremely powerful."

So has Einstein's theory passed the test so far?

"The answer is yes," Broderick said.

M87's black hole has long been intriguing for astronomers and astrophysicists. Not only is it incredibly massive, but it is also spewing a stream of particles outwards. These aren't particles that have fallen inside a black hole, since nothing can escape once it has fallen in. Instead, particles are flung out just before crossing what is called the event horizon, the point of no return around a black hole, after which the black hole consumes whatever has fallen in and grows.


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M87 and its jet of subatomic particles is seen here in a Hubble Space Telescope image travelling at nearly the speed of light. (NASA and the Hubble Heritage Team/STScI/AURA)
M87 was one of two targets for the EHT, the second being Sagittarius A*, a supermassive black hole at the centre of our galaxy, some 25,000 light-years away. This black hole has a mass of about 4.3 million times that of our sun.

Astronomers have been trying to directly image a black hole, but imaging something that is so far off and essentially invisible, requires some out-of-the-box thinking.

Enter the EHT, a collection of eight telescopes that span the globe. Instead of having a telescope that measures perhaps a few metres or tens of metres across, astronomers now have telescopes that work in unison and become "Earth-sized." This allows astronomers to collect data that provides an image of the black hole, though with some missing data.

Breaking new scientific ground
Priya Natarajan, who was not involved with the research, studies the unseen. She is a theoretical astrophysicist and professor of astronomy and physics at Yale University in New Haven, Conn., whose primary area of research centres around dark matter, dark energy and black holes.

"Black holes are definitely much more important than we thought," said Natarajan.

Specifically, they're important in understanding their influence in and around the space they occupy, which hasn't been understood.

"All the data that we have had so far has been through indirect imaging, through indirect inference," she said.

in the dark and then suddenly you can see the face of the person.- Priya Natarajan , theoretical astrophysicist
Natarajan refers to M87's black hole as an "ultramassive" black hole, one that is more than five billion times more massive than our sun — where it has "stunted" its growth meaning it can't get any bigger.

"That is super cool," Natarajan said. "That we happened to have had this one ultramassive black hole practically in our backyard."

Natarajan says that thus far, indirect observations have stretched out to perhaps 1,000 to 100,000 times from the event horizon. But now the image takes astronomers right to the edge.

"It's like you are seeing a silhouette in the dark and then suddenly you can see the face of the person," she said.

Years in the making
Trying to image a black hole has taken a lot of time: 12 years with EHT involving hundreds of people from around the world. And it's only come to be due to rapidly improving data storage and more telescopes that have been brought online.

Eight telescopes at six sites, each fitted with special equipment imaged M87's black hole in April 2017.

So why did it take two years to share the image?

"First, when you're trying to break new ground, it behooves one to be very, very careful," Broderick said. "Secondly … you often find yourself having to reinvent the wheel."

Twice the team had to develop special software tools.

"The real question is why did it only take two years?" Broderick said.


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This artist’s impression depicts a rapidly spinning supermassive black hole surrounded by an accretion disc, material around a black hole. (ESO)
Broderick, who has been with the EHT project for more than a decade, said that one of the most interesting things for him is observing the plasma that goes around the black hole: it changes on a time-scale of minutes to a week. He refers to the material as "fluff" hot luminous plasma that has very little mass compared to the black hole itself.

"Every time we go back and look at these objects again, we're getting a different version of the astrophysical fluff," Broderick said.

And from this, they may acquire a wealth of knowledge.

The 'ultimate paradox'
Natarajan is in awe of what this new announcement means.

"When you work in cosmology, there's this ultimate paradox," she says. "We are extremely significant because of all these systems of knowledge that we've created … and yet on the scale of the cosmos, we are really insignificant."


Both scientists are anxious to obtain more knowledge and perhaps eventually unify quantum theory (the study of the very small, i.e., subatomic particles) and Einstein's theory of general relativity (the study of the very big) — something that has eluded astrophysicists for years.

"You don't know what's under the rock until you turn it over," Broderick said. "This is a voyage of exploration."
 
人类文明进步中非常有意义的一天。
 
科学家们的新闻发布会直播,有个Waterloo的教授。。。

照片里的黑洞距离我们55million 光年,里面的光是5千5百万年前的。。。

 
最后编辑:
这还有一篇科普的

Black holes: What you need to know
What they are and where they're found — and how you can possibly see them
Emily Chung · CBC News · Posted: Apr 09, 2019 5:00 PM ET | Last Updated: April 9

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This is an illustration of a supermassive black hole in the middle of the ultradense galaxy M60-UCD1. The black hole's intense gravitational field warps the light of the background stars to form ring-like images just outside the dark edges of the black hole's event horizon. (NASA Goddard)
The first photograph of a black hole is set to be revealed by scientists on Wednesday. And that may leave you with some deep, dark questions about black holes. Here are some answers.

What is a black hole?
A black hole is an object in space that is so dense and has such strong gravity that no matter or light can escape its pull. Because no light can escape, it is black and invisible.

There's a boundary at the edge of a black hole called the event horizon, which is the point of no return — any light or matter that crosses that boundary is sucked into the black hole. It would need to travel faster than the speed of light to escape, which is impossible.

Anything that crosses the event horizon is destined to fall to the very centre of the black hole and be squished into a single point with infinite density, called the singularity.

If black holes are invisible, how can we detect or photograph them?
By looking for the effects of their extreme gravity, which sucks stars and gases toward it.

Also, while anything past the event horizon is invisible, outside that boundary there is sometimes a spiral disk of gas that the black hole has pulled toward — but not yet into — itself.

The gases in that accretion disk are heated up as they accelerate toward the black hole, causing them to glow extremely brightly. The colours they glow are invisible to us, but are detectable with an X-ray telescope.

With some supermassive black holes, a fraction of the matter falling toward the black hole doesn't get sucked right in. Instead, paradoxically, it gets pushed away from the black hole at close to the speed of light in two narrow beams or "jets." Like other objects in space, black holes rotate, and the jets form along the black hole's axis of rotation. Those jets are thought to be the sources of high-energy particles called cosmic rays, and they also emit light.


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A supermassive black hole with millions to billions times more mass than our sun is seen in an undated NASA artist's concept illustration. The black hole is surrounded by an accretion disk and has an outflowing jet of energetic particles, believed to be powered by the black hole's spin. (NASA/Reuters)
In theory, with a good enough telescope, you should be able to see light surrounding the black hole right to the edge of the event horizon, which is the goal of the Event Horizon Telescope. There, scientists expect to see a ring of light emitted by matter orbiting the black hole at almost the speed of light before crossing the event horizon. That ring of light is called the black hole's shadow or silhouette.

How big are black holes?
Small black holes are called stellar-mass black holes. They have masses similar to those of larger stars — about five to 20 times the mass of the sun.

The other kind is supermassive black holes, which are millions to billions of times more massive than the sun. That's the kind the Event Horizon Telescope has been trying to photograph, as bigger objects ought to be easier to see.

There is some evidence that black holes between these two sizes exist, but that has yet to be confirmed.

While black holes are very massive, that doesn't mean they take up a lot of space. Because they're so dense, they're actually quite small.

According to NASA, a black hole 20 times the mass of the sun could fit inside a ball 16 kilometres wide — the width of the Island of Montreal at its widest point.

Where are black holes found?
Supermassive black holes are found at the centre of most galaxies, including our own Milky Way. The one in our galaxy is called Sagittarius A* and is one of those the Event Horizon Telescope has been attempting to photograph (besides it being easier to try to see something that's big, it's also obviously easier to try to see something that's nearby).


event-horizon-diagram.jpg
This artist’s impression depicts a rapidly spinning supermassive black hole surrounded by an accretion disc. This thin disc of rotating material consists of the leftovers of a sun-like star that was ripped apart by the tidal forces of the black hole. Shocks in the colliding debris as well as heat generated in accretion led to a burst of light, resembling a supernova explosion. (ESO)
Sagittarius A* isn't the only black hole in our galaxy, though. Earlier this year, astronomers discovered another 12 within three light-years of it, suggesting there could be upwards of 10,000 black holes around the galactic centre.

Where do black holes come from?
Supermassive black holes are believed to form at the same time as the galaxy that surrounds them, but astronomers aren't sure exactly how.

Stellar mass black holes form when a star with a mass greater than three times that of our sun runs out of fuel. It explodes into a supernova and collapses into an extremely dense core that we know as a black hole — something predicted by Albert Einstein's general theory of relativity.

Einstein's theory also predicts the size and shape of the black holes that the Event Horizon Telescope is trying to photograph.
 
据说这是以前的煤球:D

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原来卖茶叶蛋的老太太烧的是蜂窝煤,卖大饼油条的摊点烧的是煤球。:D南京人管这些都叫煤球炉:D
你是乌衣巷的,应该知道啊。:p
抱歉!歪楼了,明明是科技贴变成煤球贴了。:tx:
 
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