A Journal of People report
With the historic first-ever image of black hole, scientists have achieved a great step forward. It is a great leap forward on behalf of the entire human society. It is a historic moment in human history. It is a great achievement by science. April 10 will be marked as the day humanity got its first look at a black hole. The achievement further confirmed Albert Einstein’s general Theory of Relativity that predicted the existence of black holes. Einstein a century ago even predicted the symmetrical shape that scientists just found.
Some 200 scientists and astronomers collectively snapped the silhouette of an object some 54 million light-years from Earth. It is 6.5 billion times more massive than the sun. The scientists have seen and taken a picture of the black hole.
This first image of the black hole is like the “shot heard round the world” that kicked off the American Revolutionary War, says Harvard University astrophysicist Avi Loeb who isn’t on the EHT team. “It’s very significant; it gives a glimpse of what the future might hold, but it doesn’t give us all the information that we want.”
Questions went unanswered for ages: What goes on in a black hole? What is there in a black hole? Scientists have tried to find out the answer.
Scientists have created the history by a network of some of the world’s most powerful radio telescopes. And, an extraordinary snap of the elusive galactic phenomenon was done.
The first image of a black hole shows a bright ring with a dark, central spot. That ring is a bright disk of gas orbiting the supermassive behemoth in the galaxy M87, and the spot is the black hole’s shadow.
The Event Horizon Telescope (EHT) team unveiled the first-ever image of a black hole at six simultaneous news conferences around the world at Washington, Brussels, Santiago, Shanghai, Taipei and Tokyo as the European Commission, European Research Council, and the EHT project detailed the findings of their mission.
Despite their enormous mass black holes are extraordinarily difficult to observe. It is impossible to photograph a black hole’s interior, as light that gets too close to its gravitational pull is lost. This point is known as the event horizon.
The team used a global network of radio telescopes in the US, Mexico, Chile, Spain and Antarctica to create one giant dish powerful enough to capture the silhouette.
US National Science Foundation Director France Córdova said: “This is a huge day in astrophysics. We’re seeing the unseeable.”
Dr Shep Doeleman informed that they surveyed the Messier 87 galaxy in an effort to be able to picture the “supermassive black hole and its core.”
“We have seen what we thought was unseeable. We have seen and taken a picture of a black hole,” Sheperd Doeleman, EHT Director and astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said April 10 in Washington, D.C., at one of seven concurrent news conferences. The results were also published in six papers in the Astrophysical Journal Letters.
The EHT image reveals the shadow of M87’s black hole on its accretion disk. Appearing as a fuzzy, asymmetrical ring, it unveils for the first time a dark abyss of one of the universe’s most mysterious objects.
“We’ve been studying black holes so long, sometimes it’s easy to forget that none of us have actually seen one,” France Córdova, director of the National Science Foundation, said in the Washington, D.C., news conference. Seeing one “is a Herculean task,” she said.
A global network of eight telescopes on five continents, collectively called the Event Horizon Telescope (EHT) helped create the historic moment.
The “event horizon” marks the distance from a black hole at which light is trapped by its enormous gravity, the point of no return.
“We have seen what we thought was unseeable,” said EHT director Sheperd Doeleman at a press briefing hosted by the National Science Foundation and EHT in Washington, D.C. “We have seen and taken a picture of a black hole.”
“We’ve been studying black holes so long, sometimes it’s easy to forget that none of us have actually seen one,” said France Cordova, director of the National Science Foundation, at the D.C. conference, one of seven concurrent briefings in cities including Brussels, Shanghai and Tokyo.
The black hole spins clockwise. It was discovered at the center of a galaxy called Messier 87 (M87).
“What we see is larger than the size of our entire solar system,” Heino Falcke, a Netherlands professor told BBC News. “And it is one of the heaviest black holes that we think exists. It is an absolute monster, the heavyweight champion of black holes in the universe.”
“You have probably seen many, many images of black holes before,” said Falcke at the press briefing. “But they were all simulations or animations. And this is precious to all of us, because this one is finally real.”
The decades-long endeavor to capture the massive black hole culminated in one week in April 2017, during which all eight telescopes observed the same areas of space and collected vast amounts of data that then took months to analyze.
But Katie Bouman, an MIT graduate student in electrical engineering and computer science, contributed a key “element” to make possible the scientists’ success. Before this revelation, three years ago, Katie Bouman led the development of a new algorithm to help astronomers produce the first image of a black hole.
According to NASA, black holes are invisible, dense remnants of a large star that died in a supernova explosion. Their intense gravity field pulls in everything around it, including light.
However, some black holes, especially supermassive ones dwelling in galaxies’ centers, stand out by voraciously accreting bright disks of gas and other material.
According to Science News, “The EHT image reveals the shadow of M87’s black hole on its accretion disk. Appearing as a fuzzy, asymmetrical ring, it unveils for the first time a dark abyss of one of the universe’s most mysterious objects.”
The picture of the black hole shows a halo of “emission from hot gas swirling around [the black hole] under the influence of strong gravity near its event horizon.”
“This has been our first chance to see the inner workings of black holes and to test a fundamental prediction of Einstein’s Theory of General Relativity,” Feryal Ozel, an astrophysicist who was the modeling and analysis lead on the project, told ABC News. “Not only the existence of a shadow that indicates a point of no return — or an event horizon — but also the size and shape of that shadow.”
“It’s a dream come true, on many levels,” she added.
A new era of astrophysics opens
The first picture of a black hole opens a new era of astrophysics.
“It’s been such a buildup,” Doeleman said. “It was just astonishment and wonder to know that you’ve uncovered a part of the universe that was off limits to us.”
Science News reports said:
The image aligns with expectations of what a black hole should look like based on Einstein’s general theory of relativity, which predicts how spacetime is warped by the extreme mass of a black hole.
The picture is “one more strong piece of evidence supporting the existence of black holes. And that, of course, helps verify general relativity,” says physicist Clifford Will of the University of Florida in Gainesville who is not on the EHT team. “Being able to actually see this shadow and to detect it is a tremendous first step.”
Earlier studies have tested general relativity by looking at the motions of stars or gas clouds near a black hole, but never at its edge. “It’s as good as it gets,” Will says. Tiptoe any closer and you’d be inside the black hole — unable to report back on the results of any experiments.
“Black hole environments are a likely place where general relativity would break down,” says EHT team member Feryal Özel, an astrophysicist at the University of Arizona in Tucson. So testing general relativity in such extreme conditions could reveal deviations from Einstein’s predictions.
Just because this first image upholds general relativity “doesn’t mean general relativity is completely fine,” she says. Many physicists think that general relativity won’t be the last word on gravity because it’s incompatible with another essential physics theory, quantum mechanics, which describes physics on very small scales.
The image also provides a new measurement of the black hole’s size and heft. “Our mass determination by just directly looking at the shadow has helped resolve a longstanding controversy,” Sera Markoff, a theoretical astrophysicist at the University of Amsterdam, said in the Washington, D.C., news conference. Estimates made using different techniques have ranged between 3.5 billion and 7.22 billion times the mass of the sun. But the new EHT measurements show that its mass is about 6.5 billion solar masses.
The scientists have also determined the behemoth’s size — its diameter stretches 38 billion kilometers — and that the black hole spins clockwise. “M87 is a monster even by supermassive black hole standards,” Markoff said.
EHT trained its sights on both M87’s black hole and Sagittarius A*, the supermassive black hole at the center of the Milky Way. But it turned out, it was easier to image M87’s monster. That black hole is 55 million light-years from Earth in the constellation Virgo, about 2,000 times as far as Sgr A*. But it’s also about 1,000 times as massive as the Milky Way’s giant, which weighs the equivalent of roughly 4 million suns. That extra heft nearly balances out M87’s distance. “The size in the sky is pretty darn similar,” says EHT team member Feryal Özel.
Due to its gravitational oomph, gases swirling around M87’s black hole move and vary in brightness more slowly than they do around the Milky Way’s. “During a single observation, Sgr A* doesn’t sit still, whereas M87 does,” says Özel, an astrophysicist at the University of Arizona in Tucson. “Just based on this ‘Does the black hole sit still and pose for me?’ point of view, we knew M87 would cooperate more.”
After more data analysis, the team hopes to solve some long-standing mysteries about black holes, such as how M87’s behemoth spews a bright jet of charged particles thousands of light-years into space.
Some black holes launch jets of charged particles thousands of light-years into space, like the one shown in this image from a simulation. Data collected to create the first image of a black hole, the one in galaxy M87, may help reveal how the jets are produced.
Jordy Davelaar et al./Radboud University, BlackHoleCam
Since the appearance of that black hole changes so quickly, the team is having to develop new techniques to analyze the data.
The measurements are taken at a wavelength the human eye cannot see, so the astronomers added color to the image. They chose “exquisite gold because this light is so hot,” said Jessica Dempsey, a co-discoverer and deputy director of the East Asian Observatory in Hawaii. “Making it these warm gold and oranges makes sense.”
“The Event Horizon Telescope allows us for the very first time to test the predictions of Einstein’s general theory of relativity around supermassive black holes in the centers of galaxies,” according to project scientist Dimitrios Psaltis of the University of Arizona. “The predicted size and shape of the shadow theory match our observations remarkably well, increasing our confidence in this century-old theory.”
Maria Zuber of the Massachusetts Institute of Technology said that “these remarkable new images of the M87 black hole prove that Einstein was right yet again.”
The telescope caught whatever light it was able to 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.
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?
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