The Fermi Bubbles (purple) straddle the galactic center, measuring roughly 25,000 light-years long from end to end. (Image credit: NASA Goddard)

Astronomers have identified the exact location where superheated gas from the supermassive black hole at the center of our galaxy is being released into the Milky Way, causing massive gassy explosions.

This newly discovered feature, acting like a colossal exhaust vent, is a bright X-ray region situated nearly 700 light-years from the galaxy's central black hole. It's connected to the black hole by a lengthy "chimney" of extremely hot gas.

According to recent research set to be published in The Astrophysical Journal, the X-ray emissions result from hot gas driven by the black hole traveling up the chimney and colliding with cooler surrounding gas at speeds exceeding 2 million mph (3.2 million km/h). This collision sends enormous shock waves rippling through the galaxy.

This discovery could provide insights into the eating habits of the supermassive black hole and shed light on some of the most mysterious objects in the galactic center.

"Astrophysicists have long been interested in the movement of material and energy from the Milky Way's center and its black hole, both to understand what's happening in our cosmic backyard and how galaxies form and evolve," said Scott Mackey, lead study author and astrophysicist at the University of Chicago. "We're really excited to find this new piece of the puzzle."

Black Hole Burps

The supermassive black hole at the Milky Way's center, Sagittarius A* (Sgr A*), is about 4 million times more massive than the sun. It resides in the dense, chaotic center of our galaxy, consuming stars, gas clouds, and other matter that venture too close to its event horizon—the point beyond which nothing can escape, not even light.

However, not all matter is consumed by the black hole. Sometimes, it is channeled by powerful magnetic fields into jets that spew away from the black hole at high speeds. In 2019, astronomers observed our black hole's erratic feeding habits by detecting two huge chimneys—one above and one below Sgr A*—that siphon hot gas away from the galactic center for hundreds of light-years in both directions.

This observation led the authors of the new study to delve deeper into the region. They used data from NASA's Chandra X-Ray Observatory, which detects extremely hot gases.

"We suspected that magnetic fields are acting as the walls of the chimney and that hot gas is traveling up through them, like smoke," Mackey explained. "Now we've discovered an exhaust vent near the top of the chimney."

The Chandra data revealed a vast vent of bright X-rays near the top of the black hole's lower chimney, where hot and cool gas continually collide. The frequency of Sgr A* ejecting gas to fill this area remains unclear, but prior X-ray studies have found evidence of large eruptions every 100 years or so.

If true, this black hole vent-and-chimney system might be the source of some of the most enigmatic objects in our galaxy—the massive Fermi bubbles and eROSITA bubbles, which straddle the galaxy's center like a giant, invisible hourglass. These mysterious bubbles, filled with high-energy gamma-rays and X-rays, extend roughly 25,000 light-years above and below the galactic center, spanning about half the width of the Milky Way.

While astronomers are unsure of the bubbles' origin, they suspect powerful energy outbursts from Sgr A* may be responsible. The newly discovered black hole vent supports this theory, linking the black hole to the base of the bubbles with a steady stream of hot gas.

"The chimneys could thereby be the channels by which sources in the Galactic center have provided the energy and particles to feed the Fermi and eROSITA bubbles," the authors noted.

The team aims to determine whether the bubbles were created by a single massive black hole outburst long ago or by a series of smaller, regular blasts over millions of years. Further study of the galactic center and the voracious black hole could help solve this cosmic mystery.

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