Revealing the Secretive Dashes in the Center of Milky Way Galaxy

An international team of astrophysicists has discovered something completely new, hidden in the center of the Milky Way galaxy.

In the early 1980s, Farhad Yousefzadeh of Northwestern University discovered a giant one-dimensional filament hanging vertically near Sagittarius A*, the central supermassive black hole of our galaxy. Now, Yousefzadeh and his collaborators have discovered a new set of filaments–but these filaments are much shorter and lie horizontally or radially, sprouting out like spokes on a wheel from a black hole.

Although the two sets of threads share many similarities, Yousefzadeh posits that they have different origins. While vertical filaments sweep across the galaxy, up to 150 light-years high, horizontal filaments look more like Morse code dots and dashes, punctuating only one side of Sagittarius A*.

The study will be published on Friday (June 2) in the Astrophysical Journal Letters.

“It was a surprise to suddenly find a new set of structures that seemed to be pointing in the direction of the black hole,” Yousefzadeh said. “I was really shocked when I saw these. We had to do a lot of work to prove that we weren’t fooling ourselves. And we found that these threads are not random but seem to be related to the flow of our black hole. By studying them, we can learn more about the direction of rotation and accretion of the black disk. It’s something Satisfying when one finds order in the middle of the chaotic field of our galactic core.”

Yousefzadeh is an expert in radio astronomy, professor of physics and astronomy at Northwestern’s Weinberg College of Arts and Sciences and a member of CIERA.

decades in the making

The new discovery may come as a surprise, but Yousefzadeh is no stranger to unearthing mysteries at the center of our galaxy, which lies 25,000 light-years from Earth. The latest study builds on four decades of his research. after First discovery of vertical filaments in 1984 With Mark Morris and Don Chance, Yousefzadeh – along with Ian Heywood and their collaborators – later discovered two giant radio-emitting bubbles near Sagittarius A*. Then, in a series of posts in 2022, Yousefzadeh (in collaboration with Heywood, Richard Arendt, and Mark Wardle) revealed nearly 1,000 vertical strings, featured in pairs and groups, often stacked evenly or side by side like strings on a harp. .

Yousifzadeh credits the influx of new discoveries with improved radio astronomy technology, particularly the South African Radio Astronomy Observatory’s (SARAO) Meerkat telescope. To identify the filaments, Yousefzadeh’s team used a technique to remove background and denoise from the MeerKAT images in order to isolate the filaments from the surrounding structures.

“Meerkat notes are a game-changer,” he said. “The advances in technology and the dedicated observation time have given us new information. It is truly a technical achievement of the radio astronomers.”

horizontal versus vertical

After studying the vertical filaments for decades, Yousefzadeh was shocked to discover horizontal filaments estimated to be around 6 million years old. “We’ve always been thinking about vertical threads and their origin,” he said. “I’m used to them being vertical. I never thought there might be others along the plane.”

While both groups consist of one-dimensional, radio-visible filaments that appear to be associated with activities in the galactic center, the similarities end there.

The vertical filaments are perpendicular to the galactic plane; The horizontal filaments are parallel to the plane but point radially toward the galactic center where the black hole is located. The vertical threads are magnetic and relative; The horizontal filaments seem to emit thermal radiation. Vertical filaments include particles moving at speeds close to the speed of light; The horizontal filaments appear to accelerate thermal matter in the molecular cloud.

There are several hundred vertical threads and a few hundred horizontal threads. And the vertical filaments, which reach a height of 150 light-years, far exceed the size of the horizontal filaments, which are only 5 to 10 light-years long. Vertical threads also decorate the space around the galactic nucleus. The horizontal filaments appear to propagate to one side only, pointing toward the black hole.

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

Our work is never complete

The new discovery is full of unknowns, and Yousefzadeh’s work to unearth its secrets has just begun. For now, he could only think of a plausible explanation for the mechanisms and origins of the new population.

“We think it originated from some kind of outflow from activity that happened a few million years ago,” Yousefzadeh said. “It seems to be the result of the interaction of that flowing material with the things near it. Our work is never complete. We always need to make new observations, constantly challenge our ideas and sharpen our analysis.”