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Hot gas bubble offers clue about supermassive black hole at the center of Milky Way

Researchers observed the gas bubble orbiting around Sagittarius A at 30% of the speed of light — or nearly 56,000 miles per second.

(CN) — To many, the existence of a black hole at the center of our galaxy is unsettling, maybe a bit scary. That Sagittarius A is a supermassive black hole, equal in mass to roughly 4 million suns, does not help matters.

But Maciek Wielgus, a Polish-born astrophysicist at the Max Planck Institute for Radio Astronomy in Bonn, Germany, is here to tell you not to worry. Sagittarius A may be big, and it may be at the center of the Milky Way, but it's still 27,000 light-years away. At that distance, it may as well be another planet or star.

"A black hole, from a distance, just behaves like a big portion of mass," Wielgus said in a recent interview conducted over Zoom. "There is nothing scary about a big portion of mass. Only when you are close, you have this weirdness. Like time stopping."

On the one hand, black holes are mysterious. What happens to objects that get sucked in, beyond the event horizon? Where do they go? On the other hand, black holes are, as Wielgus puts it, "ridiculously simple objects." According to the general theory of relativity, they only have three properties: mass, spin and charge. And scientists are pretty sure that most black holes have a neutral charge.

"One can say we understand black holes extremely well," Wielgus said. "The problem is, we don’t know if that theory is true."

He added: "Also, the problem is we are not able to learn directly about black holes. There’s no communication between what’s behind the event horizon and the outside world. The way we study black holes is how they interact with immediate environment."

Which brings us to the hot gas bubble.

This year, the public got its first look at Sagittarius A. The photo was the result of the Event Horizon Telescope (or EHT) Collaboration, which used data from eight radio telescopes all over the world, including the Atacama Large Millimeter Array, or ALMA, in the Chilean desert, the most powerful radio telescope on this planet.

Wielgus led a team of European scientists who analyzed ALMA's data in as part of the EHT collaboration. While doing so, they stumbled upon an intriguing observation: a hot gas bubble, hurtling around Sagittarius A at an astonishing pace — 30% of the speed of light. They observed the bubble for less than two hours.

In a paper published Thursday in Astronomy & Astrophysics, Wielgus and his co-authors revealed their findings support the existing theory that the flares originate from magnetic interactions in "very hot gas" orbiting close to Sagittarius A.

Of course, this observation was really a look into the past — 27,000 years into the past. But Wielgus believes Sagittarius A will routinely produce gas bubbles, the physics of which are similar to solar flares, though they differ in substance. Similar observations have been made with X-ray and infrared telescopes, but never with radio telescopes, which detect much longer wavelengths.

Wielgus described the discovery as another small step toward understanding the true nature of our very own black hole.

"We are mostly operating on the level of hints, suggestions," Wielgus saud. "Every observation is a bit of the puzzle.

"Hopefully, one day, we will be comfortable saying that we know what is going on with Sagittarius A.”

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