Mysterious undertones at the center of the Milky Way

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

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

Although the two populations have some similarities, Yosef-Zada postulates that they have different origins. The vertical lines sweep the galaxy and rise to a height of up to 150 light years, while the horizontal lines look more like dots and lines of Morse code, and are only on one side of Sagittarius A*.

The study was published June 2 in The Astrophysical Journal Letters.

MeerKAT image of the center of the galaxy with position angles in different colors of all long vertical filaments.
Credit: Farhad Yusef-Zadeh/Northwestern University

"It was a surprise to suddenly find a new population of structures that seemed to be pointing in the direction of the black hole," Yosef-Zada said. "I was really shocked when I saw them. We worked hard to determine that we were not fooling ourselves. And we found that these filaments are not random but seem to be related to the emissions of our black hole. Their study will allow us to learn more about the spin of the black hole and the direction of the accretion discs. There is satisfaction when you find Order in the midst of the chaotic domain of our galaxy's core."

MeerKAT image of the center of the galaxy with position angles in different colors of all radial short filaments.
Credit: Farhad Yusef-Zadeh/Northwestern University

The new discovery may be surprising, but discovering mysteries at the center of our galaxy 25,000 light-years away from Earth is no stranger to Yosef-Zada. After first discovering the vertical tones in 1984 with Mark Morris and Don Chance, Yosef-Zeda with Ian Heywood and their collaborators later discovered two giant bubbles emitting radio signals near Sagittarius A*. Then, in a series of publications in 2022, Yosef-Zada (along with Haywood, Richard Arnett, and Mike Wardell) discovered nearly a thousand vertical tones, which appeared in pairs and clusters, often stacked at equal distances or next to each other like harp strings.

Yosef-Zeda says that the reason for the many new discoveries is improvements in radio astronomy technology, specifically the MeerKAT telescope at the SARAO Observatory in DRAP. To precisely locate Nimot, Yosef-Zeda's team used a technique to remove the background and smooth noise from the MeerKAT images to isolate the Nimots from surrounding structures.

"The new MeerKAT observations have changed the situation," he said. "Technology advances and dedicated viewing time have given us new information. This is a real achievement from Radio Astronomers."