Lubbock, Texas (new version) With the help of Alexandra Titarenko, a NASA Einstein Fellow at Texas Tech University, astronomers have unveiled the first image of the supermassive black hole at the center of our Milky Way. This result provides compelling evidence that the object is indeed a black hole and provides valuable clues about the functioning of such giant planets, which are thought to reside at the center of most galaxies. The image was produced by a global research team called the Event Horizon Telescope (EHT) Collaboration, using observations from a global network of radio telescopes.
The image is a long-awaited look at the massive object at the center of our galaxy. Scientists have previously seen stars orbiting an invisible, compact and very massive object at the center of the Milky Way. This strongly suggests that this object – known as Sagittarius A* (Sgr A*, pronounced “sadge-ay-star”) – is a black hole, and today’s image provides the first direct visual evidence of it.
Although we can’t see the black hole itself, because it’s completely dark, the glowing gas around it reveals a distinctive sign: a dark central region (called a “shadow”) surrounded by a bright ring-like structure. The new view captures light being bent by the black hole’s powerful gravitational pull, which is four million times the mass of our sun.
“We were amazed how much the size of the ring matched Einstein’s predictions
“General relativity,” said Jeffrey Bauer, EHT project scientist from the Institute of Astronomy and Astrophysics at Academia Sinica in Taipei. “These unprecedented observations have greatly improved our understanding of what is happening at the heart of our galaxy and provide new insights into how these giant black holes interact with their surroundings.”
The EHT team’s findings are published today in a special issue of Astrophysical Journal Letters.
Since the black hole is about 27,000 light-years away from Earth, it appears to us that its size in the sky is the same as the size of a cake on the moon. To image it, the team created the powerful EHT, which linked together eight radio observatories located across the planet to form a single “Earth-size” hypothetical telescope. He observed the EHT Sgr A* on several nights, and collected data for several hours, similar to using a long exposure time on a camera.
Tetarenko previously spent several years working at one of the EHT’s telescopes, the James Clerk Maxwell Telescope, located on the slopes of Maunakea in Hawaii.
“My time in Hawaii provided me with an amazing opportunity to participate in the EHT,” said Tetarenko, a postdoctoral researcher in the Department of Physics and Astronomy. “From taking notes to analyzing data with several brilliant colleagues, it is very exciting to see how far we can push our instruments and how much we can discover about some of the most amazing things in our world: black holes!”
The breakthrough comes on the heels of the 2019 EHT collaboration’s release of the first image of a black hole, called M87*, at the center of the more distant galaxy Messier 87.
The two black holes look remarkably similar, even though our galaxy’s black hole is a thousand times smaller and less massive than M87*.
“We have two completely different types of galaxies and two very different masses of black holes, but near the edge of these black holes they look amazingly similar,” said Sera Markov, co-chair of the EHT Science Council and professor of theoretical astrophysics. at the University of Amsterdam in the Netherlands. “This tells us that general relativity governs these things closely, and any differences we see further away must be due to differences in the material surrounding black holes.”
This feat was much more difficult than the M87*, although Sgr A* is much closer to us. EHT scientist Chi Kwan Chan, of the Steward Observatory, Department of Astronomy and Data Science Institute at the University of Arizona, explains, “Gas near black holes moves at the same speed — roughly the speed of light — around both Sgr A* and M87*. But when it takes The gas takes days to weeks to orbit the larger M87*, it in the much smaller Sgr A* completes an orbit in just minutes.This means that the brightness and pattern of the gas around Sgr A* was changing rapidly as the EHT Collaboration team was observing it – a bit like trying to take a picture Clear puppy chasing its tail fast.”
The researchers had to develop sophisticated new instruments responsible for the movement of gas around Sgr A*. While the M87* was an easier and more stable target, with nearly all images looking the same, this was not the case for Sgr A*. The image of the black hole Sgr A* is an average of the various images extracted by the team, finally revealing the giant lurking at the center of our galaxy for the first time.
This effort is made possible by the ingenuity of more than 300 researchers from 80 institutes around the world that together make up the EHT Collaboration. In addition to developing sophisticated tools to overcome Sgr A* imaging challenges, the team worked rigorously for five years, using supercomputers to integrate and analyze their data, all while assembling an unprecedented library of simulated black holes for comparison with observations.
Tetarenko, one of the principal coordinators of the EHT’s Time Domain Working Group, specializes in studying rapidly changing emissions from black holes. Her work helped solve the problem of photographing a rapidly changing target.
“The light we’re picking up from material orbiting the black hole has been changing in brightness on minute time scales, so it was critical that we discern this contrast before we could properly calibrate the data and create an image,” she said.
Scientists are especially excited to finally get images of two black holes of very different sizes, providing an opportunity to understand how they compare and contrast. They are also beginning to use the new data to test theories and models of how gas behaves around supermassive black holes. This process is not yet fully understood but is believed to play a major role in shaping the formation and evolution of galaxies.
“We can now study the differences between these two supermassive black holes to gain valuable new clues about how this important process works,” said EHT scientist Keiichi Asada of the Institute of Astronomy and Astrophysics at Academia Sinica in Taipei. “We have images of two black holes – one at the big end and one at the small end of supermassive black holes in the universe – so we can go further in testing the behavior of gravity in these extreme environments than ever before.”
EHT progress continues: The main observing campaign in March 2022 included more telescopes. The ongoing expansion of the EHT network and significant technological updates will allow scientists to share more impressive images as well as films of black holes in the near future.
Tetarenko remotely participated in this year’s EHT observations, connecting to the James Clerk Maxwell Telescope in Hawaii from right here in Lubbock. As the EHT network continues to expand, it hopes to eventually be able to use the EHT to observe smaller stellar-mass black holes within our galaxy.
“It was great to continue to be a part of the EHT observations this year; two weeks of long sleepless nights are worth it,” she said. “The next generation EHT network is an incredibly exciting future tool that will be transformative for studying the jets of matter emanating from these wormholes. black star-mass.”
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