Following half a century of research efforts, scientists have successfully identified wind flowing from the massive black hole located at our galaxy’s core, revealing it produces more of a mild cosmic breeze than the violent storms observed elsewhere in the universe.
Researchers utilized observations from Chile’s ALMA telescope along with NASA’s Chandra X-ray Observatory to examine the space surrounding the black hole known as Sagittarius A*, abbreviated as Sgr A*.
The team identified an enormous cone-shaped hollow region containing hot, electrically charged gas next to Sgr A*, which they determined was carved out by wind flowing from the black hole that either displaced or heated the cold gas previously occupying that area. According to the researchers, only a supermassive black hole could generate the energy required to form such a cavity.
These cosmic objects possess incredibly dense matter with gravitational pull so powerful that light cannot escape their grasp. Most galaxies contain a supermassive black hole at their center that draws in surrounding gas and materials.
Researchers theorized decades ago that any active supermassive black hole would naturally eject some gas and materials into space due to fundamental physics – either as outward-flowing wind or concentrated jets. While they had previously observed this phenomenon in countless supermassive black holes throughout other galaxies, scientists had been unable to prove that Sgr A* exhibited similar behavior until now.
“This discovery resolves a half-century-old mystery,” said Lena Murchikova, a professor of physics and astronomy at Northwestern University in Illinois and co-leader of the study published this week in the Astrophysical Journal Letters.
Sgr A* contains approximately 4 million times our sun’s mass and sits roughly 26,000 light-years away from Earth. One light-year equals the distance light covers in a year – 5.9 trillion miles (9.5 trillion km). Compared to similar objects in other galaxies, it ranks as less massive and currently exists in a relatively calm phase.
The pointed end of the cone-shaped cavity begins near Sgr A* and spreads outward. Though researchers cannot determine the cavity’s complete size since it extends beyond their observation range, Murchikova estimated it might stretch approximately 6.5 light-years in length.
Due to Sgr A*’s current peaceful condition, the wind it produces lacks the intensity observed from other supermassive black holes. Northwestern University astronomer and study co-leader Mark Gorski compared its winds to Earth’s weather patterns.
“It is a gentle breeze coming from our supermassive black hole. It doesn’t appear to be strong enough to drastically restructure the galactic center,” Gorski said.
“Supermassive black holes spend most of their time in this quiet, gentle state. However, sometimes they go through outbursts ranging from thunderstorms to the most violent of hurricanes. Their most intense winds or jets can completely disrupt their host galaxies and regions well beyond,” Gorski said.
When gas and other materials spiral toward a black hole, they approach light speed, generating sufficient energy and pressure to launch some material outward.
“While some gas keeps falling in, other gas is ejected. In fact, more of the gas is ejected than falls into the black hole. This ejected gas is the wind we are talking about,” Murchikova said. “When we look at distant galaxies far-far away, it is much easier to see violent phenomena. We see huge, powerful jets ripping through the galaxy and everything else in their path. We see violent winds ejecting nearly all gas from their galaxies.”
The distinction between a jet and wind relates purely to shape.
“Jets are narrow and don’t expand very much as they leave their source, often producing a beam of matter. Winds, however, are wider and expand as they leave their source. It’s almost like the difference between a laser pointer and a flashlight,” Gorski said.
