Meet the black hole at the center of our galaxy: Scientists just took its picture for the first time




  • In Science
  • 2022-05-12 13:29:41Z
  • By Business Insider
black hole photo orange ring sagitarrius A*
black hole photo orange ring sagitarrius A*  
  • A new image reveals the supermassive black hole at the center of the Milky Way for the first time.

  • In 2019, the Event Horizon Telescope captured the first-ever image of a supermassive black hole.

  • A glimpse of Sagittarius A* will help us understand the evolution of our galaxy, researchers said.

For the first time, take a good look at the supermassive black hole churning at the center of our galaxy.

Hundreds of scientists worked together to capture the first-ever image of the Milky Way's central black hole, called Sagittarius A* (pronounced "A-star"). Research institutions across the planet unveiled the picture in simultaneous press conferences on Thursday.

In the photo, a brilliant fuzzy ring of orange and yellow glows around a dark center - the accretion disk, a swirl of superheated material, circling the event horizon, where not even light can escape the black hole's gravity. That disk allows scientists to capture the black hole's silhouette, since the object swallows all forms of light, making it impossible to photograph directly.

Researchers took this stunning photo through the Event Horizon Telescope (EHT), an international collaboration that involves 300 international scientists and eight radio observatories around the world. Xavier Barcons, director general of the European Southern Observatory, said at a press conference that the groundbreaking result is a timely reminder of what we can achieve when countries work together.

Sara Issaoun of Harvard, an EHT collaborator, said that researchers gathered direct evidence that Sagittarius A* is a black hole, with a size of about 52 arcseconds in the sky.

"This appears the same size in the sky as a donut on the Moon," she said at a press conference.

In 2019, the Event Horizon Telescope captured the first-ever image of a supermassive black hole located 53.5 million light-years away. That picture showed a supermassive black hole at the center of another galaxy called Messier 87, or M87, more than 50 million light-years away. To achieve the photographic feat, the researchers linked telescopes across the planet to focus on the same object all together, creating a virtual observatory the size of Earth.

first image of a black hole m87
first image of a black hole m87  

For many EHT scientists, the next step was obvious: turn this groundbreaking cosmic lens to the heart of the Milky Way.

"We were all amazed that the image of Sagittarius A* looked so similar to the image of the black hole at the center of the M87 galaxy," Sera Markoff, co-chair of the EHT Science Council and astrophysicist at the University of Amsterdam, told reporters on Thursday. "This tells us that general relativity governs these objects up close, and any differences we see further away must be due to differences in the material that surrounds the black holes," Markoff said.

Scientists think every galaxy has a supermassive black hole at its center, from the very early days of the galaxy's birth. A major astronomical mystery is how black holes and their galaxies evolve together.

"Understanding black holes, at any level, addresses fundamental mysteries of the universe. If we're ever going to learn something that is completely unknown to us, it will be from doing something like studying black holes," Shep Doeleman, an astrophysicist at Harvard University and founding director of the EHT collaboration, told Insider ahead of Thursday's announcement.

"It's a wonderful time to be alive," he added.

'Seeing is believing'

Previous Nobel Prize-winning research has demonstrated that the supermassive compact object at the center of the Milky Way must be a black hole, based on the way that its gravity affects nearby stars. Doeleman compared that research to finding bones with teeth marks on the jungle floor and concluding there is a large predator in the area.

"Contrast that with taking a camera out and taking a snapshot of a lion," he said, adding, "Seeing is believing, in a certain sense."

Sagittarius A* possesses the mass of 4 million suns, creating one of the most powerful gravitational forces in the universe, devouring the matter that falls into its event horizon. There's nothing to fear, though. It's about 27,000 light-years from Earth.

Sagittarius A
Sagittarius A  

Even though it's closer to us, this black hole was much more difficult to image than M87. It's 1,000 times less massive than M87, which means the accretion disk orbits multiple times in just a few hours.

"During one night of observing, it's constantly shapeshifting. So it's very difficult to combine all the observations from a single night and to make a still image. It's like having somebody move around while you're keeping the shutter open on your camera. Everything gets very blurry," Doeleman said.

Though it's hard to capture, that speed makes Sagittarius A* ideal for studying the dynamics of black holes and how they evolve over time. It could take months of observing M87 to see the flares and feeding activities that occur on Sagittarius A* in just one week.

The new image of the behemoth at the center of our galaxy could hint at even more exciting discoveries to come.

Working toward video of the Milky Way's black hole

These images are opening a new field of black-hole studies, and it doesn't stop with still pictures. EHT has branched out into a second project, called next-generation EHT (ngEHT), to make the first videos of black holes.

The group is working to add more telescopes to its network and leverage new computer technology to process 10 times more data from those telescopes, Doeleman told Insider in 2019. In doing so, he said, they could capture video of both Sagittarius A* and their original photo subject, M87, in about five years.

Now, two years in, EHT has 11 telescopes in its network, from Chile to Greenland to France to the South Pole. Doeleman said this week that the collaboration still has to double its telescope fleet.

He hopes that eventually, videos can reveal what a still image cannot: how those black holes devour matter, how they launch X-ray jets from their poles, and how matter orbits around them.

"We want to see it move and live and breathe. So we want to capture the dynamics of black holes in motion," Doeleman said.

The first videos will probably be jerky and low-resolution, but EHT plans to keep imaging black holes in more and more detail.

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