The Milky Way’s huge black hole was missing a key feature. Scientists say they finally detected it - CNN

- After more than 50 years of searching, scientists have found evidence of wind from Sagittarius A*, the supermassive black hole at the center of our galaxy.

- Using advanced radio telescopes in Chile, the researchers mapped cold gas around the black hole and identified a cavity about 3 light-years long.

- The discovery may solve a long-standing mystery about why our closest black hole appeared to lack the outflows observed from supermassive black holes in other galaxies.

Scientists say they have detected evidence of cosmic-scale wind coming from a supermassive black hole at the center of our galaxy, potentially solving one of the longest-standing mysteries in astronomy.

Sagittarius A*, a gigantic black hole with the mass of about 4 million suns, has puzzled the scientific community for more than 50 years. The laws of physics dictate that, like all black holes, the object should not just consume material but also expel some in the form of wind or jets. However, Sagittarius A* has been strangely quiet. Despite decades of searching, scientists could only gather clues of wind eruptions dating back more than 20,000 years but none more recent.

“This is our closest and best studied black hole,” said Mark Gorski, a research assistant professor at Northwestern University in Evanston, Illinois. “It’s the one we can resolve and see all of the physics around it, and yet it didn’t seem to have a wind. Every black hole in the universe behaves in this one way, but the one that’s closest to us is different. That was a huge problem.”

Now, after five years of observations, Gorski and Lena Murchikova, an assistant professor of physics and astronomy at Northwestern, believe they have found signs of the missing wind. The duo created a highly detailed image of the black hole’s surrounding area. Within the image, Gorski and Murchikova spotted a large, cone-shaped cavity devoid of cold gas.

The feature could only have been sculpted by a wind of hot gas coming directly from the object itself, according to the researchers, who are co-lead authors of a study on the discovery published June 4 in the journal The Astrophysical Journal Letters.

“The black hole wind acts like a hair dryer,” Gorski said. “It blows hot turbulent air into a colder, denser material, like your wet hair. The wind is warm and strong enough to heat and blow the water out of your wet hair and move the wet hair around a bit — but not strong enough to blow the hair off your head completely.” Similarly, the hot gas in the wind from the black hole left a clear signature by swiping away the surrounding cold gas, the study has suggested.

Scientists have previously observed similar outflows, both in the form of tight jets and broad winds, from the supermassive black holes at the centers of other galaxies. These outflows are a critical part of how a black hole pumps energy into its host galaxy and regulates its growth, according to Christopher Reynolds, a professor of astronomy at the University of Maryland, College Park, who was not involved with the study.

“These outflows have proved really elusive when looking at our own supermassive black hole — until now,” he wrote in an email. “This study presents a pretty compelling case that a wind from our galaxy’s supermassive black hole has pushed outwards through the surrounding dust and gas. They haven’t actually seen the wind itself, but its presence is quite clear. This required very careful analysis of almost 5 years of data from the world’s most sensitive radio telescope — a real tour de force.”

Black holes are astronomical objects with a gravity so strong that not even light can escape them. Most big galaxies have a central supermassive black hole — up to billions of times the mass of our sun. Smaller black holes are the remnants of large dead stars, but the origin of the supermassive ones is poorly understood.

Nothing can escape the black hole’s threshold, called the event horizon. However, the material that swirls around the black hole can heat up and glow due to friction and tidal forces, emitting radio waves and X-rays. When the black hole feeds on gas, the object unleashes particles in the form of wind or jets that move at nearly the speed of light, traveling up to thousands of light-years into space. A light-year is the distance light travels in one year, which is 5.88 trillion miles (9.46 trillion kilometers).