A discovery solves a mystery: a "gentle breeze" emanates from a black hole.
After five decades of attempts, astronomers have finally discovered winds emanating from the supermassive black hole at the center of our Milky Way galaxy, describing them as a "gentle breeze". Researchers, using data from the ALMA observatory telescope in Chile and NASA's Chandra X-ray Observatory, have identified the region surrounding the black hole in space, known as Sagittarius A*, according to Reuters. They also observed a huge cone-shaped cavity filled with hot, electrically charged gas next to the black hole, and concluded that it was formed by winds emanating from it that displaced or heated the cold gas that filled the area, explaining that the energy needed to form such a cavity could only come from a supermassive black hole. Scientists have assumed for decades that any active supermassive black hole will, by its very physical nature, eject some gas and other material into space, either as an outward wind or as a concentrated jet stream.
A mystery that lasted half a century
“This discovery solves a half-century-old mystery,” said Lena Murchikova, a professor of physics and astronomy at Northwestern University in Illinois and co-author of the study published this week in the journal Astrophysical Letters. Murchikova stated, "While some gas continues to fall inwards, another portion is ejected outwards. In fact, the amount of gas ejected outwards exceeds that which falls into the black hole. This ejected gas is the wind we are talking about."
She added, "When we look at very distant galaxies, it is easier to observe violent phenomena. We see enormous and powerful jet streams cutting through the galaxy and everything in their path, and we see fierce winds throwing almost all the gas out of their galaxies."
4 million times the mass of our sun
Sagittarius A* is about four million times the mass of our Sun and is located approximately 26,000 light-years from Earth. A light-year is the distance light travels in one year, or 9.5 trillion kilometers. It is not as massive as some of its counterparts in other galaxies, and scientists say it is in a relatively dormant state. The cone-shaped end of the cavity originates in the immediate vicinity of Arc (A) and extends outward. While researchers are still unsure of the cavity's size because it is beyond their field of observation, Murchikova said it could extend to about 6.5 light-years. Because of the current state of Sagittarius A, the winds it generates are not as intense as those observed with other supermassive black holes.
"A gentle breeze"
Northwestern University astronomer Mark Gursky, who co-authored the study, likened the Sagittarius wind to weather on Earth. "It's a gentle breeze coming from our supermassive black hole," he said. "It doesn't appear to be strong enough to drastically reshape the center of the galaxy." He added, "Usually, supermassive black holes are in this calm and gentle state, but sometimes they go through bouts of activity ranging from thunderstorms to the most violent hurricanes. Their more intense winds or currents can disrupt their host galaxies and even regions farther away." As the gas and other materials enter a spiral path towards the black hole, they reach speeds close to the speed of light, generating enough energy and pressure to eject some of them outwards.
It is worth noting that black holes are extremely dense objects with such immense gravity that even light cannot escape them. Galaxies typically contain a supermassive giant black hole at their center that attracts surrounding gas and other material.
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