
MeerKAT image of the galactic center with vertical and horizontal filaments
Farhad Yusef-Zadeh/Northwestern University
The center of our galaxy is filled with hundreds of strange streaks of hot gas, which may have formed due to an explosion of Sagittarius A*, the Milky Way’s resident supermassive black hole.
Farhad Yusef-Zadeh at Northwestern University in Illinois and his colleagues found these filaments using data from the MeerKAT radio telescope in South Africa. In the 1980s, Yusef-Zadeh discovered a set of vertical filaments aligned perpendicular to the galaxy’s disk, but the new horizontal filaments were completely unexpected.
“The vertical filaments are aligned with the galaxy’s magnetic field, but the rest should be aligned randomly,” he says. “The pattern I saw took me by surprise – at first I couldn’t believe it.”
While the vertical filaments are up to 150 light-years tall, the horizontal ones are only 5-10 light-years long, all pointing to Sagittarius A*. These horizontal filaments appear to be made of gas, unlike the vertical filaments, which are most likely made of high-energy electrons. They also appear to be moving away from Sagittarius A*, towards the outer areas of the galaxy where Earth is located.
The orientations of the filaments and their movement indicate that they may have formed when a jet exploded out of Sagittarius A*, stretching any gas the jet passed through through in tendrils. Their positions relatively close to the black hole indicate that it is very likely that this explosion began about 6 million years ago and is still going on, although with a much lower intensity now.
Studies of the area just off Sagittarius A* have hinted that such an explosion occurred, but have not yet been confirmed. “We really want to reconstruct these larger-scale structures with the smallest scale around the black hole and show that there really is this jet coming out along the disk of the galaxy,” says Yusef-Zadeh. “This could have really profound implications for our understanding of the black hole’s spin axis.”
This could mean that Sagittarius A*’s axis of rotation is perpendicular to that of the galaxy as a whole, which would be an important clue to how our galaxy formed and how it now interacts with its central black hole. .
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