In Global Effort, Shanghai Astronomers Capture Milky Way’s Black

It took five years for a team of scientists to construct the first-ever image of the invisible celestial object.                                      

For the first time, astronomers have captured an image of the supermassive black hole at the center of the Milky Way, the galaxy of stars and planets that includes our own.

Scientists at the Shanghai Astronomical Observatory, who are a part of the international black hole hunting mission called the Event Horizon Telescope collaboration, revealed the picture during one of the six simultaneous press conferences held around the world on Thursday.

The fuzzy image shows the shadow of the Milky Way’s black hole, dubbed Sagittarius A* or Sgr A*, surrounded by heated gas and dust displayed in orange. The gravitational pull of Sgr A*, which has a mass over 4 million times that of the sun, is strong enough to devour everything, including light, that comes too close to it. As a result, the black hole itself is unseeable.

To create the image, the EHT team linked together eight telescopes located in different parts of the world, including the Tianma telescope in suburban Shanghai, so that the observatory network could function like a powerful telescope nearly the size of Earth.

The Milky Way’s black hole was captured in 2017, when the team coordinated the telescopes to point at Sgr A* for five days. But it took the EHT team, consisting of over 300 astronomers from around the world (including 17 from China), five years to parse the data and painstakingly construct the image.

Detailed data was published on Thursday in 10 separated papers in the journal Astrophysical Journal Letters.

“I had always hoped to know what Earth’s closest supermassive black hole looks like,” Ge Jian, an astronomer at the Shanghai Astronomical Observatory who is not involved in EHT, told Sixth Tone. “This picture is another milestone in humankind’s understanding of the universe. … I’m also very happy to see such great collaboration between scientists around the globe.”

In 2019, the Event Horizon Telescope released the first-ever picture of a black hole, which is located at the center of the M87 galaxy, about 55 million light years away from Earth.

Jiang Wu, a member of the EHT team and an astronomer at the Shanghai Astronomical Observatory, said during the Thursday press conference that the making of the Sgr A* image was a lot more difficult than that of M87’s black hole, partly because interstellar gas and dust between Earth and Sgr A* blurred the signal.

In addition, Sgr A*’s gas ring circles the black hole a lot more rapidly than that of M87. Jiang said it was extremely difficult to take a clear picture of such a fast moving object.

The COVID-19 pandemic also disrupted the research, making data sharing — which is mainly done through shipping hard drives across continents because the internet can’t handle the amounts of data involved — and collaboration much more challenging, said Vincent Fish, an astronomer at the MIT Haystack Observatory in Massachusetts, U.S., and an EHT scientist, during the press conference held in Washington D.C.

Despite the differences between the two captured black holes, both images share a similar donut-like pattern.

“These unprecedented observations have greatly improved our understanding of what happens at the very center of our galaxy and offer new insights on how these giant black holes interact with their surroundings,” said EHT Project Scientist Geoffrey Bower from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, in a statement released Thursday.

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Astronomers are hoping more and better telescopes can join the Event Horizon Telescope to improve future images’ accuracy or even capture videos of black holes and their moving gas rings, said Shen Zhiqiang, the director of the Shanghai Astronomical Observatory, during the press conference.

He added that China is planning a new telescope in northwestern Qinghai province that could be part of the next generation Event Horizon Telescope.

This article was updated on May 13 to add comment from Ge Jian.

Editor: Kevin Schoenmakers.

(Header image: The first image of Sgr A*, the supermassive black hole at the center of our galaxy, with an added black background to fit wider screens. NASA)