- Astronomers found first direct evidence of a powerful wind from Sagittarius A* black hole
- Five years of ALMA data revealed a three-light-year cone-shaped cavity in surrounding gas
- Chandra X-ray data confirmed hot gas is pushed outward at thousands of kilometres per second
Astronomers have found the first direct evidence of a powerful outflow, or "wind," streaming from Sagittarius A* (Sgr A*), the supermassive black hole at the centre of the Milky Way. The discovery resolves a 50-year-old mystery that has eluded scientists since the 1970s. While astrophysics models long predicted that matter accelerating to near light-speed before falling into a black hole should trigger massive jets and winds. But there was no observational proof.
The breakthrough findings, published on June 4 in The Astrophysical Journal Letters, reveal how researchers finally understood a small part of our galactic core.
By analysing five years of data from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the team mapped the cold molecular gas surrounding Sgr A* with unprecedented sharpness.
After filtering out the black hole's intense radio glare, they discovered a striking, three-light-year-long, cone-shaped cavity in the gas cloud.
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Data from NASA's Chandra X-ray Observatory confirmed it, showing that this empty void is filled with hot, high-speed gas being pushed outward from the black hole at thousands of kilometres per second.
"Unless a black hole exists in a perfect vacuum, it must blow a wind somehow. And there is no perfect vacuum in the universe," study co-lead Mark Gorski, an astrophysicist at Northwestern University, said in a statement.
"With new observations, this is the first time we've had a clean enough view to see the wind's imprint. We looked at the data and said, 'There it is. There is the thing that everybody's been looking for for 50 years.'"
This "wind" has likely been blowing for at least 20,000 years. Because Sgr A* is currently in a quiet, "dormant" state.
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"We were the first to show that molecular gas very, very close to the black hole is feeding it," said Elena Murchikova, a Northwestern professor who co-led the study.
"The wind is not powerful, and its direction probably wanders with time. It shows that our black hole is not unique, and our place in the universe is not unique."
Peering into the heart of our own galaxy is incredibly difficult. "To observe our own black hole, we have to look through the plane of our galaxy," Murchikova explained.
"That means we have to peer through gas, dust and ionized structures, and you can't really see through all of that easily."
The landmark detection finally explains how even quiet black holes steadily interact with their environments and influence star formation and gas dynamics across their host galaxies.
It also gives astronomers a perfect, local baseline to study how dormant black holes shape galactic evolution over billions of years.
