See the first image ever taken of a supermassive black hole

[Wolfano]

See the first image ever taken of a supermassive black hole

 

 

For the first time ever, humanity can gaze at an actual photograph of a supermassive black hole. It’s an achievement that’s taken supercomputers, eight telescopes stationed around the world, hundreds of researchers, and vast amounts of data. The results from this project, called the Event Horizon Telescope (EHT), were announced today at joint press conferences live-streamed around the world. In addition to providing a picture that will quickly be incorporated into teaching materials around the world, the results helped to confirm (again) Einstein’s theory of general relativity, and it gave astrophysicists an unprecedented close-up of these enigmatic, dense celestial phenomena.

“Black holes are the most mysterious objects in the Universe,” Sheperd Doeleman, the project director of the Event Horizon Telescope, said at a press conference today before unveiling the image.

The picture shows the black hole at the center of the huge galaxy Messier 87 (M87), which is located about 53 million light-years away from Earth.

 

 

The black hole in this galaxy has a mass that the Event Horizon Telescope researchers estimate to be 6 billion times more massive than our Sun. In addition to being gargantuan, M87’s black hole was already intriguing to researchers. In some early pictures of the galaxy, they noticed a massive jet of plasma streaming out from its center. Scientists think that the jet is made of material that never quite made it into the event horizon of the black hole. Instead, their observations suggest that the movement of M87’s black hole (which researchers believe is spinning rapidly) accelerates subatomic particles and sends them shooting out into the universe, a beacon to distant astronomers.

 

The Event Horizon Telescope is not a traditional telescope; rather, it refers to a group of eight radio telescopes that are stationed on five continents, which all observed the same areas of space over the course of one week in April 2017.

According to the Event Horizon Telescope, a conventional telescope would have to be approximately the size of Earth in order to take this particular snapshot of the black hole at the center of M87. “This is a picture you would have seen if you had eyes as big as the Earth and were observing in radio,” Dimitrios Psaltis, an Event Horizon Telescope project scientist at the University of Arizona, recently told The Verge. Individually, none of the telescopes measured up. But by coordinating their efforts, the researchers were able to zero in M87, collecting massive amounts of data in the process.

 

 

While the observations took just one week in April 2017 to gather, actually sorting through the vast amounts of data took months. Just getting it all into one place was a huge challenge. Writing in Nature News in 2017, Davide Castelvecchi noted that a “typical night will yield about as much data as a year’s worth of experiments at the Large Hadron Collider outside Geneva, Switzerland.” All of that data was recorded onto discs and then physically sent to centralized locations where it was analyzed by a supercomputer for months in order to get the image we see today.

Before this picture was released to the public, the image itself — and the data used to create it — went through one more step: a rigorous peer-review process, vetted by researchers in the field who were not part of the project.

Researchers with the Event Horizon Telescope project had four main scientific goals when they started this project. The first was simple: take a picture of a black hole. Check.

The other three were more complicated. Researchers also wanted to understand more about how black holes grow and what makes material orbiting the black hole eventually fall in. The researchers hope that the answer to that might also explain why the material surrounding Sagittarius A* (the black hole at the center of our own galaxy) is unusually dim for material circling a supermassive black hole. The Event Horizon Telescope also wanted to get a better idea of why supermassive black holes at the center of some galaxies, like elliptical galaxy M87, seemed to help propel massive streams of subatomic particles out of the galaxy and into the broader universe.

Finally, the researchers wanted a chance to check Einstein’s work. The famous scientist’s theory of general relativity is over 100 years old, and it’s held up really well over the past century. He predicted the existence of gravitational waves long before humanity had the means to detect them, and his theory also predicted that the silhouette or “shadow” of a black hole would look circular. So far, so good.

 

Source

[xpkRAKE]

It's better than I expected it to be, even if it does look like a glazed donut 🍩

[Karlston]

We now have images of the environment at a black hole’s event horizon

Black holes exist, and we've now seen light from next to the event horizon.

Enlarge / The first image of the environment around a black hole. As a matter of fact, it's not all dark.

National Science Foundation

Two years ago, telescopes around the world turned their attention to two supermassive black holes. Now, after a massive computational effort, their data has been combined in a way that allowed them to function as a single, Earth-sized telescope. The results are an unprecedented glimpse of the environment around supermassive black holes, and they confirm that relativity still works under the most extreme gravitational forces.

Enlarge / The environment near the black hole appears to change on very short time scales, though we're not sure about the significance of this. White circles reflect the resolving power of the Event Horizon Telescope.

Astrophysical Journal

The black hole in question is a supermassive one at the center of the galaxy M87, 55 million light years away. M87 is an active galaxy where the black hole is feeding on matter and ejecting jets of material. The image is made from photons that were temporarily trapped in orbit around the black hole. Here, the intense gravity causes matter—and even space itself—to move at approximately the speed of light. The eventual escape of these photons causes a bright ring to appear around the black hole itself, with the details of the ring reflecting the physics of the black hole.

A monster

At a press conference this morning, Avery Broderick of the Perimeter Institute described what the images tell us. One key finding is that the object is a black hole, at least as we've understood black holes using relativity. It does not have any visible surface, and the "shadow" of light it creates is circular within the limits of our observations. We can also tell that it spins clockwise. All of the properties we can infer from these images are consistent with relativity. "I was a little stunned that it matched the predictions we made so well," said Broderick.

 

The University of Amsterdam's Sera Markoff said that the size of the black hole provided a new estimate of its mass; she called it "really a monster, even by black hole standards." It's roughly the size of the Solar System, but it has a mass that is 6.5 billion times that of our Sun. This actually resolved a conflict between two other measures of its mass, one from the motion of gas clouds nearby, the other from tracking the stars orbiting it. This may help us refine estimates of mass for black holes elsewhere.

 

Missing so far is any discussion of the jets launched by black holes that are ingesting mass. Some process causes a portion of the material falling toward the black hole to get ejected at roughly light speed in two jets. It was hoped that the Event Horizon Telescope would help clarify how these jets start, but there was no mention of the topic in the press conference. Details may reside in one of the six papers released today.

 

When asked how he reacted to the first images, project lead Shep Doeleman said it was intensely satisfying. "We could have seen blobs, and we have seen blobs," he said, talking about past results. "We saw something that was so true."

The telescope

The Event Horizon Telescope isn't a telescope in the traditional sense. Instead, it's a collection of telescopes scattered around the globe. In its current iteration, it includes hardware from Hawaii to Europe, and from the South Pole to Greenland, though not all of these were active during the initial observations. The telescope is created by a process called interferometry, which uses light captured at different locations to build an image with a resolution similar to that of a telescope the size of the most distant locations.

 

Interferometry has been used for facilities like ALMA, the Atacama Large Millimeter/submillimeter Array, where telescopes can be spread across 16km of desert. In theory, there's no upper limit on the size of the array, but there are several challenges. To know which photons originated at the same time at the source, you need very precise location and timing information on each of the sites. And you still have to gather sufficient photons in order to see anything. In general, that means atomic clocks (which had to be installed at many of the locations) and extremely precise GPS measurements built up over time. For the Event Horizon Telescope, the large collecting area of ALMA, combined with choosing a wavelength where supermassive black holes are very bright, ensured sufficient photons.

 

The net result is a telescope that can do the equivalent of reading the year stamped on a coin in Los Angeles from New York City—assuming the coin was glowing at radio wavelengths. There's no way we can do better without relying on hardware that's not located on Earth.

 

Since a number of the sites are arrays, the initial data obtained for the Event Horizon observations was, in digital terms, enormous. So the people behind the Event Horizon telescope built a set of data recorders capable of gathering information at a 16 Gigabits/second rate and spreading it across 32 hard drives. Each site in the telescope received four of these data recording units; at the end of the observations, they were shipped to one of two data processing centers—in total, half a ton of hard drives were shipped around.

 

The process of reconstructing an image, then, is a colossal computing task, which is part of the reason that there's been a significant lag from the observations made in April of 2017. (Waiting for spring in the Southern Hemisphere so the data from the South Pole Telescope could be transported out was another source of delay.)

What are we looking for?

The telescope did its imaging while pointed at two different targets: the supermassive black hole at the center of our galaxy and one in the large galaxy M87. Part of that was simply geometry, in that having hardware scattered across one side of the Earth limits the locations that can be imaged. But part of the reason these two were chosen is because they are very different examples of supermassive black holes.

 

Our galaxy's central black hole is a relatively quiet one. While there is some matter in its vicinity, it hasn't built up the features typical of active central black holes: a large disk of brightly glowing material and huge jets sent out of both poles at nearly the speed of light. Those, however, seem to be present on the Event Horizon Telescope's second target, the central black hole of galaxy M87. That's a larger, active black hole, and it has at least one jet (it's oriented so we can't see the second) that extends for thousands of light years.

 

Obviously, given their nature, we won't be looking at these black holes themselves. But we can learn a great deal about the environment around them. For example, there's no consensus about how, precisely, jets of material get accelerated to nearly the speed of light. The Event Horizon Telescope was designed to give us the best images yet of the base of the jets by showing how they're related to the other structures near the black hole.

 

Another feature that scientists were interested in is what's called the "shadow" of the black hole. The intense gravity near black holes warps the space around it, pulling some of it around for multiple orbits of the object. This has strange effects on the light originating from the material, creating a pattern that's referred to as the black hole's shadow. Since that shadow depends on the paths that light can travel around the black hole, it provides a sensitive test of relativity and could rule out some alternative theories of gravity.

 

The shadow also depends on the mass and spin of the black hole, so it provides information regarding its physical properties.

 

Source: We now have images of the environment at a black hole’s event horizon (Ars Technica)

 

Poster's Note: The article contains an image slideshow. To see it, please visit the above link.

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eye of sauron 

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