It’s the first direct observation to confirm the existence of a black hole, known as Sagittarius A*, as the beating heart of the Milky Way.
Black holes do not emit light, but the image shows the shadow of the black hole surrounded by a bright ring, the light is bent by the black hole’s gravity. Astronomers have said that the black hole is four million times larger than our sun.
Michael Johnson, Astrophysicist, Center for Astrophysics: “For decades, astronomers have wondered what lies at the heart of our galaxy, attracting stars into tight orbits with its immense gravity” | Harvard and Smithsonian, in a statement.
“Using an image (Event Horizon Telescope, or EHT), we zoomed in a thousand times closer to these orbits, where gravity grows a million times stronger. At this close range, a black hole accelerates matter to approach the speed of light and bends photons’ paths in twisted (spacetime).”
The black hole is about 27,000 light-years away from Earth. Our solar system is located in one of the spiral arms of the Milky Way, which is why we are so far from the galactic center. If we could see this in the night sky, the black hole would appear to be the same size as a donut sitting on the moon.
“We were amazed at how well the ring size matched expectations from Einstein’s general theory of relativity,” EHT project scientist Jeffrey Bauer of the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, said in a statement.
“These unprecedented observations have greatly improved our understanding of what is happening in (the center of) our galaxy, and provide new insights into how these giant black holes interact with their surroundings.”
Searching for a black hole
It took astronomers five years to capture and confirm this image and discovery. Previously, scientists observed stars orbiting some invisible massive objects in the center of the galaxy.
Ramesh Narayan, theoretical astrophysicist at the Center for Astrophysics: “Now we see that the black hole swallows nearby gas and light, pulling them into a bottomless crater” | Harvard and Smithsonian, in a statement. “This image confirms decades of theoretical work to understand how black holes eat away.”
This discovery was made possible by more than 300 researchers from 80 institutions working with the network of eight different radio telescopes around the world that make up the Event Horizon Telescope.
The telescope is named after the “event horizon,” the point where no light can escape from the black hole. This global telescope network essentially constitutes a single “Earth-size” virtual telescope when all eight are linked and the observations are side by side.
While the two images look alike, arc A* is more than 1,000 times smaller 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 institute. University of Amsterdam in a statement.
“This tells us that (Einstein’s theory of) general relativity governs these things closely, and any differences we see further away must be due to differences in the matter surrounding black holes.”
Impossible to take a picture
Although the Milky Way’s black hole is closer to Earth, it was difficult to photograph.
“Gas near black holes is moving at the same speed — roughly the same speed of light — around both Sgr A* and M87*,” EHT scientist Chi-kwan Chan at the Steward Observatory and Department of Astronomy and Data Science Institute of the University of Arizona said in a statement. .
“But when the gas takes days to weeks to orbit the larger M87*, in the much smaller Sgr A* it completes an orbit in just a few minutes. This means that the brightness and pattern of the gas around Sgr A* were changing rapidly as the EHT collaboration was observing it—a bit like Trying to take a clear picture of a puppy chasing its tail fast.”
The global network of astronomers had to develop new instruments to allow the rapid movement of gas around Sagittarius A*. The resulting image is the average of the various images the team took. Capturing the image of Sagittarius A* was like taking a picture of a grain of salt in New York City with a camera in Los Angeles, according to Caltech researchers.
“This image from the Event Horizon Telescope requires more than just taking an image from telescopes on high mountaintops. It is the product of both technically challenging telescope observations and innovative computational algorithms,” said Katherine Bowman, a Rosenberg researcher and assistant professor of computing and mathematics sciences, electrical engineering. and astronomy at the California Institute of Technology, during a press conference.
Each telescope has been pushed to its maximum limit, which is called the diffraction limit, or the maximum number of minute features it can see.
“And that’s basically the level we’re seeing here,” Johnson said at the press conference. “It’s unclear because to make the image clearer, we need to move our telescopes away or move to higher frequencies.”
Obtaining images of two completely different black holes will allow astronomers to determine their similarities and differences and better understand how gas behaves around supermassive black holes, which may contribute to the formation and evolution of galaxies. Black holes are believed to be at the center of most galaxies, and act as their engines.
Meanwhile, the EHT team is working to expand the telescope’s network and make upgrades that could lead to more stunning images and even movies of black holes in the future.
Capturing a black hole in motion can show how it changes over time and what the gas does as it orbits the black hole. Bowman and EHT member Antonio Fuentes, who will join Caltech as a postdoctoral researcher in October, are developing methods that will allow them to link black hole images together to reflect this motion.
This “first direct image of the gentle giant at the center of our galaxy” is just the beginning, said Ferial Ozil, a member of the EHT Science Council and professor of astronomy and physics and associate dean of research at the University of Arizona. Press conference.
“This image is a testament to what we can achieve, when we bring our brightest minds together as a global research community to make the seemingly impossible and possible,” National Science Foundation Director Sithuraman Panchanathan said in a statement. “Language, continents, and even the galaxy cannot stand in the way of what humanity can achieve when we come together for the common good of all.”