An image of the supermassive black hole in the heart of the Milky Way was taken, giving the first direct view of the “gentle giant” at the center of our galaxy.
The black hole itself, known as Sagittarius A *, cannot be seen because no light or matter can escape its gravitational grip. But its shadow is traced by a glowing, fuzzy ring of light and matter that spins on the precipice at a speed close to light.
The image was taken by the Event Horizon (EHT) telescope, a network of eight radio telescopes spanning locations from Antarctica to Spain and Chile that created the first image of a black hole in a galaxy called Messier 87 in 2019.
Prof. Sera Markov, an astrophysicist at the University of Amsterdam and co-chair of the EHT Scientific Council, said: “The Black Hole on the Milky Way was our main goal, it is our closest supermassive black hole and that is why we did it. something in the first place. It’s been a 100-year search for these things, and so, from a scientific point of view, it’s a huge deal. “
The image provides convincing evidence that there is a black hole in the center of the Milky Way, which was the working assumption of basic astronomy. Few scientists have continued to speculate about the possibility of other exotic objects, such as boson stars or lumps of dark matter.
“I am personally happy that it really breaks through the fact that there is definitely a black hole in the center of our galaxy,” said Dr. Ziri Yunsey, a member of the EHT collaboration based at University College London.
To the untrained eye, the latest image may look roughly similar to that of the black hole, M87 *, but the two objects are extremely different, according to the EHT team.
Sagittarius A * consumes only a small trickle of material, unlike the typical depiction of black holes as violent, predatory monsters from space. “If SgrA * was human, he would consume only one grain of rice every million years,” said Michael Johnson of the Harvard-Smithsonian Center for Astrophysics.
M87 *, in contrast, is one of the largest black holes in the universe and has huge, powerful jets that emit light and matter from their poles into intergalactic space.
M87 *, shot in 2019. Photo: EHT / Zuma / Rex / Shutterstock
“Sgr A * gives us a glimpse into the much more standard state of black holes: quiet and still,” Johnson said. “[It] it’s exciting because it’s common. “
Recent observations also appear to indicate that the angle of rotation of our black hole is not exactly aligned with the galactic plane, but is deflected by about 30 degrees and hints at spectacular magnetic activity similar to that observed in the solar atmosphere. Beyond science, astronomers have recognized an emotional connection to finally seeing the mysterious object around which our native galaxy revolves.
“It’s another donut, but it’s our donut,” Yunsi said.
Although astronomically local at 26,000 light-years, the observation of SgrA * proved more challenging than expected. The team spent five years analyzing data obtained during a random clear sky on several continents in April 2017.
Sagittarius A * is relatively small, which means that the dust and gas in its accretion disk circulate in a few minutes, not weeks, creating a moving target from one observation to the next. Markoff compares the observations to trying to photograph a puppy chasing its tail with a slow shutter speed camera. Scientists also had to peek across the galactic plane and filter stars and dust clouds from their images. Some combination of these factors – and probably some extreme black hole phenomenon – explain the bright spots in the image.
“We have not foreseen how evasive and elusive it will be,” Yunsi said. “It was a really difficult picture to take. It’s hard to overestimate that. “
The EHT captures radiation emitted by particles in the accretion disk that heat up to billions of degrees as it orbits the black hole before sinking into the central vortex. The spot halo of the image shows light bent by the powerful gravity of the black hole, which is 4 meters more massive than that of our sun.
Ultimately, scientists hope that observing a number of black holes – quite dormant like our own and turbulent giants like M87 * – could help answer a chicken-and-egg-style question about galaxy evolution.
“This is an open question in galactic formation and evolution. We don’t know which comes first, the galaxy or the black hole, “said Professor Carol Mandel, an astrophysicist at the University of Bath who is not part of the EHT collaboration.
“From a technological point of view, it’s insane that we can do that,” she said of the latest images.
The results of the EHT team were published Thursday in a special issue of the Astrophysical Journal Letters.
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