UMass astronomers help uncover details of black hole at ‘the center of our galaxy’: Global scientific effort identifies ‘gentle giant’ Sagittarius A*

  • Gopal Narayanan, right, a UMass Amherst reseacher in the Event Horizon Telescope Collaboration, is shown a few years ago with Shep Doeleman, of Harvard University, near the Large Millimeter Telescope in Mexico. HARVARD/UMASS AMHERST

  • The 50-meter diameter Large Millimeter Telescope in Mexico is the largest, most sensitive single-aperture instrument and has been part of the global effort to identify the black hole known as Sagittarius A (asterisk). UMass Amherst/Smith College/James Lowenthal

  • This image shows the black hole known as Sagittarius A (asterick), located in the center of the Milky Way Galaxy. Event Horizon Telescope Collaboration

Staff Writer
Published: 5/12/2022 4:37:58 PM

AMHERST — Three years ago, scientists unveiled the first image ever made of a black hole, showing fiery, gravity-twisted light swirling around a black core — and researchers at the University of Massachusetts Amherst played a part in that discovery.

Now, scientists have produced an image of another massive black hole, this one at the center of our own Milky Way Galaxy — and UMass researchers have again been part of that effort, one that involved over 300 scientists from around the world, compiling data drawn from eight different radio telescopes, including the Large Millimeter Telescope (LMT), operated jointly by UMass and Mexico atop a 15,000-foot Mexican mountain.

Black holes, astronomers believe, are cosmic bodies of extremely intense gravity from which neither light nor matter can escape, which makes them very difficult to photograph; light is bent and twisted by gravity, as are superheated gas and dust (black holes can be formed by the death of a star).

But Gopal Narayanan, a UMass astronomer who’s been involved with the research project for several years — it’s known as the Event Horizon Telescope (EHT), which links telescopes across the globe to capture myriad images — says hard work, determination, and close collaboration among researchers have now helped confirm something that Albert Einstein theorized over a century ago.

“This has been a huge effort,” Narayanan said in a call Thursday from the National Science Foundation in Washington, where he was part of a press conference at which images of the new black hole, known as Sagittarius A* (or Sag A-star) were shown.

“There’s been a lot of sweat and blood expended, and it’s nice to be able to show the result,” he added.

Narayanan is the leader of a UMass research team of about 10 people that’s been part of the larger global effort to identify and photograph Sagittarius A*, near the border of the Sagittarius and Scorpius constellations and 4 million times the mass of our sun.

Narayanan said compiling data at the LMT is a challenge itself, given the thin oxygen and the cold atop Sierra Negra, one of Mexico’s highest peaks, where the giant telescope is located.

“It’s really challenging physically to work there,” said Narayanan, who in the past has typically gone to the site eight to 10 times a year, spending a week or more at the LMT during those visits (the pandemic limited visits during the last two years). “But the payoff is being able to push the boundaries of science and learn more about the universe.”

In the press conference at the National Science Foundation, another researcher, Feryal Ozel of the University of Arizona, called Sagittarius A* “the gentle giant in the center of our galaxy,” noting that while other black holes generally gobble up huge amounts of galactic material, this one is relatively calm: “It’s eating very little.”

Ozel noted that the black hole photographed in 2019, in a galaxy called M87 that is about 53 million light-years from Earth, is much larger that Sagittarius A* — about 6 billion times the mass of our sun. Sagittarius A*, about 27,000 light-years away, is also shrouded by gases that “burble and gurgle,” she noted, making it more difficult to photograph.

“It took quite a while to be able to refine our images,” she said.

But she added that all this new information has enhanced human understanding of black holes and confirmed the validity of Einstein’s Theory of Relativity and his maxims about gravity.

Katie Bauman, a researcher at the California Institute of Technology, likened compiling all the different amounts of data on Sagittarius A* to trying to recognize the melody of a song played on a piano with missing keys.

The rapid movement of gases around Sagittaruis A* also made it seem “like there was a change in key to that song every time you listened to it,” added Bauman.

But that made the ultimate discovery and confirmation all the sweeter, she said: “What’s more cool than seeing the black hole at the center of our own Milky Way?”

Peter Schloerb, another member of the UMass research team, said the LMT, which the university operates in conjunction with Mexico’s National Institute of Astrophysics, Optics and Electronics, has been a key link in the group of eight radio telescopes worldwide used to identify Sagittarius A*. He calls the LMT an “anchor station” that coordinates closely with telescopes in Chile, Hawaii and other sites in the Western Hemisphere.

The LMT, according to its website, is the world’s “largest single-dish, steerable millimeter-wavelength telescope,” giving it access to radio waves that other telescopes find more difficult to discern. For that reason, Schloerb said, the LMT can likely play an important role in the next stage of Sagittarius A* research, which scientists say is to capture additional images from the black hole to produce a “movie” of the gases that swirl around it.

By coordinating with additional, smaller telescopes, Schloerb noted, the LMT can help produce the myriad photos that would be needed to create such a moving image.

Narayanan, his UMass colleague, noted that other people at the university, such as graduate and doctoral students, have also been part of these black hole research efforts over the years. That, plus the contributions from so many other researchers around the globe, gives him “a great sense of camaraderie,” he said.

“I’m excited to see so many young people, young women, and from so many different backgrounds, taking part in this,” he said. “I really enjoy that collaborative nature of science, that we can feel we’ve played a part in expanding our understanding of the world.”

Steve Pfarrer can be reached at spfarrer@gazettenet.com.

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