Something wholly new-found to be hidden in Milky Way’s center

Mysterious dashes revealed in Milky Way’s center.

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Almost 40 years ago, astrophysicists discovered prototype magnetized radio filaments in the Galactic Center. An international team of astrophysicists has found something new hidden in the center of the Milky Way galaxy. 

These filaments are found to be much shorter and lie horizontally or radially, spreading out like spokes on a wheel from the black hole.

Despite the similarities between the two populations of filaments, they are not related. The horizontal filaments, which only punctuate one side of Sagittarius A*, contrast sharply with the vertical filaments, which span the galaxy and reach heights of up to 150 light-years.

Northwestern University’s Farhad Yusef-Zadeh said, “It was a surprise to suddenly find a new population of structures that seem to be pointing toward the black hole. I was stunned when I saw these. We had to do much work to establish that we weren’t fooling ourselves. And we found that these filaments are not random but appear tied to our black hole’s outflow. We could learn more about the black hole’s spin and accretion disk orientation by studying them. It is satisfying when one finds order in a middle of a chaotic field of the nucleus of our galaxy.”

Yusef-Zadeh attributes the explosion of new findings to advancements in radio astronomy equipment, particularly the MeerKAT telescope at the South African Radio Astronomy Observatory (SARAO). To distinguish the filaments from surrounding structures, Yusef-Zadeh’s team utilized a method to eliminate the background and smooth the noise from MeerKAT images.

Sagittarius A*
Diagram of the outflow from Sagittarius A*. Credit: Northwestern University

Yusef-Zadeh said, “The new MeerKAT observations have been a game changer. The advancement of technology and dedicated observing time have given us new information. It’s a technical achievement from radio astronomers.”

After spending decades studying the vertical filaments, Yusef-Zadeh was startled to find their horizontal cousins, which he calculates are roughly 6 million years old.

The parallels between the two populations cease there, albeit both consist of one-dimensional filaments that can be seen with radio waves and seem connected to events in the galactic center.

The horizontal strands are parallel to the galactic plane but point radially in the direction of the galaxy’s center, where the black hole is located. The vertical filaments are perpendicular to the galactic plane. The horizontal filaments appear to radiate heat radiation, while the vertical filaments are relativistic and magnetic.

The horizontal filaments appear to accelerate heated material in a molecular cloud, while the vertical filaments include particles traveling at speeds close to the speed of light. There are a few hundred horizontal filaments but many hundreds of vertical filaments. Furthermore, the horizontal filaments, which are just 5 to 10 light-years long, are far smaller than the vertical filaments, which can reach heights of up to 150 light-years. The area surrounding the galaxy’s center is similarly decorated with vertical filaments; the horizontal filaments spread to only one side, pointing toward the black hole.

Yusef-Zadeh said“One of the most important implications of radial outflow that we have detected is the orientation of the accretion disk and the jet-driven outflow from Sagittarius A* along the galactic plane.”

“We think they must have originated with some outflow from an activity a few million years ago. It results from interacting that outflowing material with objects near it. Our work is never complete. We always need to make new observations and continually challenge our ideas and tighten up our analysis.”

Journal Reference:

  1. F. Yusef-Zadeh, R. G. Arendt, M. Wardle, and I. Heywood. The Population of the Galactic Center Filaments: Position Angle Distribution Reveals a Degree-scale Collimated Outflow from Sgr A* along the Galactic Plane. The Astrophysical Journal Letters. DOI 10.3847/2041-8213/acd54b
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