Astronomers find “a new population of structures that seem to be pointing in the direction of the black hole.”

Researchers discover a new type of filament structure in the center of our galaxy, potentially linked to the outflow from our central supermassive black hole.

A global collaboration of astrophysicists has uncovered a novel astronomical phenomenon located at the heart of our Milky Way galaxy.

Going back to the 1980s, Farhad Yusef-Zadeh from Northwestern University identified massive, one-dimensional strands hanging vertically near Sagittarius A*, the supermassive black hole at the core of our galaxy. Recently, Yusef-Zadeh and his research team have revealed a new set of strands — however, these are shorter and are aligned horizontally or radially, spreading from the black hole like spokes from a wheel.

Despite a few common traits between the two sets of strands, Yusef-Zadeh believes they originate from different sources. The vertical strands are grand in scale, reaching heights of up to 150 light-years, as they trace their path across the galaxy. Contrarily, the horizontal strands resemble the familiar patterns of Morse code, adorning only one flank of Sagittarius A*.

The research findings were released today in The Astrophysical Journal Letters.

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

The recent breakthrough may come as an astonishment, but Yusef-Zadeh is well-versed in unveiling enigmas centered in our galaxy, a colossal 25,000 light-years distant from our planet. His latest research represents an expansion of his four-decade-long scientific journey. Together with Mark Morris and Don Chance, Yusef-Zadeh first encountered vertical filaments in 1984. In subsequent collaboration with Ian Heywood and other researchers, they discovered two massive bubbles emitting radio waves near Sagittarius A*. Subsequently, through a collection of published works in 2022, Yusef-Zadeh and his team, including Heywood, Richard Arent, and Mark Wardle, exposed the presence of nearly a thousand vertical filaments. These filaments were often paired or clustered, frequently appearing as evenly spaced or aligned like the strings of a harp.

Yusef-Zadeh attributes this wave of newfound discoveries to advancements in radio astronomy technology, specifically the capabilities of the South African Radio Astronomy Observatory’s (SARAO) MeerKAT telescope. In their pursuit to isolate these filaments, Yusef-Zadeh’s team employed a method to eliminate background interference and reduce the noise from MeerKAT imagery, allowing them to distinguish these filaments from adjacent structures.

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

For years, Yusef-Zadeh has been engaged in the study of vertical cosmic structures, making it an astonishing revelation to discover horizontal counterparts, believed to be around 6 million years old.

“We have always been thinking about vertical filaments and their origin,” he adds. “I’m used to them being vertical. I never considered there might be others along the plane.”

Despite both types comprising one-dimensional structures visible through radio waves and seeming to be linked with the center of the galaxy, their similarities largely cease at this point.

Vertical cosmic structures align perpendicularly with the plane of the galaxy, while the horizontal ones run parallel to it, pointing in the direction of the galaxy’s heart, where the black hole resides. Vertical filaments are characterized by their magnetic nature and their relative speed, whereas horizontal filaments are distinguished by their thermal radiation emissions. The vertical filaments involve particles moving at nearly the speed of light, whereas the horizontal filaments appear to speed up the thermal matter within a molecular cloud. The number of vertical filaments outnumbers the horizontal ones, with several hundred vertical compared to just a few hundred horizontal. The vertical structures, stretching up to 150 light-years, considerably overshadow the horizontal filaments, which only measure between 5 to 10 light-years. Furthermore, vertical filaments beautify the space surrounding the galaxy’s core, whereas the horizontal filaments seem to extend only to one side, aiming toward the black hole.

“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,” Yusef-Zadeh remarks.

The recent findings teem with mysteries, and Yusef-Zadeh’s exploratory journey to decipher its enigmas has merely taken off. At this stage, he can only speculate on possible theories concerning the mechanisms and beginnings of this newly discovered cosmic group.

“We think they must have originated with some kind of outflow from an activity that happened a few million years ago,” Yusef-Zadeh points out. “It seems to be the result of an interaction of 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.”

Image Credit: Farhad Yusef-Zadeh/Northwestern University