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Astronomie - Something no human has seen before: The first-ever photograph of a black hole

4.04.2019

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They've captured our imaginations for decades, but we've never actually photographed a black hole before – until now.

Next Wednesday, at several press briefings around the world, scientists will apparently unveil humanity's first-ever photo of a black hole, the European Space Agency said in a statement. Specifically, the photo will be of "Sagittarius A," the supermassive black hole that's at the center of our Milky Way galaxy.

But aren't black holes, well, black, and thus invisible, so none of our telescopes can "see" them? Yes – therefore the image we're likely to see will be of the "event horizon," the edge of the black hole where light can't escape. 

Even that will be challenging, however, as the black hole at the center of our galaxy is "shrouded in a thick cloud of dust and gas," according to Science Alert. Even more confounding is that spacetime around a black hole is "weird."

(Black holes are actually collapsed stars, with gravity so strong that even light cannot escape their grasp.) So the photo may show a dark blob surrounded by a ring of bright light, according to Yahoo. 

Science News said that the black hole research was done using the Event Horizon Telescope, a network of eight radio observatories around the world.

Whatever the announcement is next week, "we’ll almost certainly be seeing something no human has ever seen before," Popular Mechanics reported.

Press briefings will be held simultaneously in the U.S, Brussels, Santiago, Shanghai, Taipei and Tokyo. 

Quelle: USA Today

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Update: 9.04.2019

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The first photo of a black hole is coming Wednesday. What are we going to see and what will we learn?

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Astronomers will supposedly release the first-ever photo of a black hole on Wednesday. What's all the fuss about, and what will we learn from it?

What's a black hole?

First of all, black holes are collapsed stars with gravity so strong that even light cannot escape their grasp. One of the black holes we're expecting to get a glimpse of this week – known as Sagittarius A – is the "supermassive" one that's at the center of our Milky Way galaxy.

Supermassive black holes are millions to billions times more massive than our sun, and appear to be in the center of almost all galaxies, the National Science Foundation said. 

Astronomers this week are also expected to release images of another supermassive black hole, one that's 53.5 million light-years away.

This computer-simulated image shows a supermassive black hole at the core of a galaxy. The black region in the center represents the black hole’s event horizon, where no light can escape the massive object’s gravitational grip. The black hole’s powerful gravity distorts space around it like a funhouse mirror.
NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel (STScI)

What will we see?

As its name suggests, a black hole is black, so it'll be impossible to "see" against the black backdrop of space. But nearby objects, such as the event horizon – the edge of the black hole where light can't escape – could be visible. 

So the photo may show a dark blob surrounded by a ring of bright light, according to Yahoo.

But that also might be a challenge, since the black hole at the center of our galaxy is "shrouded in a thick cloud of dust and gas," Science Alert reported. 

What's "taking" the photo?

As you might expect, this won't be your run-of-the-mill photo of the night sky from your smartphone. Images will come from the Event Horizon Telescope, a collection of telescopes around the world specifically designed to peer at black holes. The telescopes are in Chile, Hawaii, Arizona, Mexico, Spain and at the South Pole.

The telescope will catch whatever light it can detect from near the black hole. By combining the data from the various telescopes placed around the world, the Event Horizon Telescope has as much magnifying power as a telescope the size of the entire Earth.

What does this have to do with Einstein's theories of relativity?

The image from the black hole may give us more insight into Albert Einstein’s theory of general relativity, which he came up with in 1915. According to CNET, the shape of the black hole's event horizon could prove Einstein's theory or possibly cast new doubt upon it.

But even if it casts doubt, the finding would not necessarily mean that his theory is wrong, but it would imply that we have more physics to understand, the Event Horizon Telescope website reported.

The discovery will be unveiled Wednesday by the National Science Foundation at a 9 a.m. ET press conference.

Quelle: USA Today

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Update: 10.04.2019

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Scientists have obtained the first image of a black hole, using Event Horizon Telescope observations of the center of the galaxy M87. The image shows a bright ring formed as light bends in the intense gravity around a black hole that is 6.5 billion times more massive than the Sun.

Wissenschaftler haben das erste Bild eines Schwarzen Lochs erhalten, indem sie Event Horizon Teleskop-Beobachtungen des Zentrums der Galaxie M87 verwenden. Das Bild zeigt einen hellen Ring, der sich bildet, wenn sich das Licht in der intensiven Schwerkraft um ein schwarzes Loch dreht, das 6,5 Milliarden Mal massiver ist als die Sonne.

Quelle: The Event Horizon Telescope

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The EHT is not a single physical telescope; instead, it's an array of linked radio dishes across the globe, creating an Earth-sized virtual telescope.  

A black hole is an object with such strong gravitational pull that nothing, even light, can escape it. The black hole itself is invisible (don't expect to see anything like the special effects in Interstellar), but the surrounding matter illuminates its "shadow," which can be seen. The particular black holes the EHT is focusing on are the central black hole in our own galaxy as well as the supermassive black hole in the center of galaxy M87, and getting a glimpse of these is a pretty big deal. 

Quelle: Mashable

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Update: 11.04.2019

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Black Hole Image Makes History; NASA Telescopes Coordinated Observations

A black hole and its shadow have been captured in an image for the first time, a historic feat by an international network of radio telescopes called the Event Horizon Telescope (EHT). EHT is an international collaboration whose support in the U.S. includes the National Science Foundation.

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Using the Event Horizon Telescope, scientists obtained an image of the black hole at the center of galaxy M87, outlined by emission from hot gas swirling around it under the influence of strong gravity near its event horizon.
Credits: Event Horizon Telescope collaboration et al.

A black hole is an extremely dense object from which no light can escape. Anything that comes within a black hole’s “event horizon,” its point of no return, will be consumed, never to re-emerge, because of the black hole’s unimaginably strong gravity. By its very nature, a black hole cannot be seen, but the hot disk of material that encircles it shines bright. Against a bright backdrop, such as this disk, a black hole appears to cast a shadow.   

 

The stunning new image shows the shadow of the supermassive black hole in the center of Messier 87 (M87), an elliptical galaxy some 55 million light-years from Earth. This black hole is 6.5 billion times the mass of the Sun. Catching its shadow involved eight ground-based radio telescopes around the globe, operating together as if they were one telescope the size of our entire planet. 

 

“This is an amazing accomplishment by the EHT team,” said Paul Hertz, director of the astrophysics division at NASA Headquarters in Washington. “Years ago, we thought we would have to build a very large space telescope to image a black hole. By getting radio telescopes around the world to work in concert like one instrument, the EHT team achieved this, decades ahead of time.”

 

To complement the EHT findings, several NASA spacecraft were part of a large effort, coordinated by the EHT’s Multiwavelength Working Group, to observe the black hole using different wavelengths of light. As part of this effort,NASA’s Chandra X-ray Observatory, Nuclear Spectroscopic Telescope Array (NuSTAR) and Neil Gehrels Swift Observatory space telescope missions, all attuned to different varieties of X-ray light, turned their gaze to the M87 black hole around the same time as the EHT in April 2017. NASA’s Fermi Gamma-ray Space Telescope was also watching for changes in gamma-ray light from M87 during the EHT observations. If EHT observed changes in the structure of the black hole’s environment, data from these missions and other telescopes could be used to help figure out what was going on. 

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Chandra X-ray Observatory close-up of the core of the M87 galaxy.
Credits: NASA/CXC/Villanova University/J. Neilsen

While NASA observations did not directly trace out the historic image, astronomers used data from NASA’s Chandra and NuSTAR satellites to measure the X-ray brightness of M87’s jet. Scientists used this information to compare their models of the jet and disk around the black hole with the EHT observations. Other insights may come as researchers continue to pore over these data. 

 

There are many remaining questions about black holes that the coordinated NASA observations may help answer. Mysteries linger about why particles get such a huge energy boost around black holes, forming dramatic jets that surge away from the poles of black holes at nearly the speed of light. When material falls into the black hole, where does the energy go? 

 

“X-rays help us connect what’s happening to the particles near the event horizon with what we can measure with our telescopes,” said Joey Neilsen, an astronomer at Villanova University in Pennsylvania, who led the Chandra and NuSTAR analysis on behalf of the EHT’s Multiwavelength Working Group. 

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Chandra X-ray Observatory close-up of the core of the M87 galaxy.
Credits: NASA/CXC/Villanova University/J. Neilsen

NASA space telescopes have previously studied a jet extending more than 1,000 light-years away from the center of M87. The jet is made of particles traveling near the speed of light, shooting out at high energies from close to the event horizon. The EHT was designed in part to study the origin of this jet and others like it. A blob of matter in the jet called HST-1, discovered by Hubble astronomers in 1999, has undergone a mysterious cycle of brightening and dimming.

 

Chandra, NuSTAR, Swift and Fermi, as well as NASA’s Neutron star Interior Composition Explorer (NICER) experiment on the International Space Station, also looked at the black hole at the center of our own Milky Way galaxy, called Sagittarius A*, in coordination with EHT.   

 

Getting so many different telescopes on the ground and in space to all look toward the same celestial object is a huge undertaking in and of itself, scientists emphasize. 

 

“Scheduling all of these coordinated observations was a really hard problem for both the EHT and the Chandra and NuSTAR mission planners,” Neilsen said. “They did really incredible work to get us the data that we have, and we’re exceedingly grateful.”

 

Neilsen and colleagues who were part of the coordinated observations will be working on dissecting the entire spectrum of light coming from the M87 black hole, all the way from low-energy radio waves to high-energy gamma rays. With so much data from EHT and other telescopes, scientists may have years of discoveries ahead. 

Quelle: NASA

 
 
 

 

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