Almost 1,000 Mysterious Magnetic Filaments Discovered Around The Milky Way's Core

The new MeerKAT image of the Galactic core shows new and previously-known radio features such as supernova remnants, compact star-forming regions, and thealmost 1,000 mysterious radio filaments. Image Credit: I. Heywood, SARAO.

Thirty-five years ago, researchers discovered that around the center of our galaxy, there are mysterious long magnetic filaments. Their origin has perplexed scientists for decades – but new observations might change what we currently know about them.

As reported in The Astrophysical Journal Letters, the new radio observations reveal that astronomers have only been looking at a small fraction of these filaments: There are at least 10 times more out there than previously known, pushing the total number to nearly 1,000 of these 150-light-year-long cosmic strands.  

“We have studied individual filaments for a long time with a myopic view,” the paper's lead author and original discoverer of the filaments Farhad Yusef-Zadeh, from Northwestern University, said in a statement

“Now, we finally see the big picture — a panoramic view filled with an abundance of filaments. Just examining a few filaments makes it difficult to draw any real conclusion about what they are and where they came from. This is a watershed in furthering our understanding of these structures.”

Close-up of the harp-like filaments. Image Credit: Northwestern University/SAORO/Oxford University

The discovery of so many filaments allowed the team to get more insights. For example, it seems unlikely that they are related to supernova remnants. It's more likely they are a product of Sagittarius A*, the supermassive black hole at the center of the galaxy. They might be connected to the radio bubbles discovered at the center of the Milky Way a few years ago.

The team could confirm that magnetic fields along the filaments are amplified. This characteristic is shared by all the filaments, and could only be confirmed by the larger number of examples the astronomers now have.

“If you were from another planet, for example, and you encountered one very tall person on Earth, you might assume all people are tall. But if you do statistics across a population of people, you can find the average height. That’s exactly what we’re doing,” Yusef-Zadeh added. “We can find the strength of magnetic fields, their lengths, their orientations and the spectrum of radiation.”

However, there is still so much to find out. Why do they cluster? Why are they evenly spaced, like the string of a harp?

“They almost resemble the regular spacing in solar loops,” Yusef-Zadeh said. “We still don’t know why they come in clusters or understand how they separate, and we don’t know how these regular spacings happen. Every time we answer one question, multiple other questions arise.”

This looks like the work of a regular telescope but it was done using radio waves. The energetic superbubble that surrounds Sagittarius A* is the main focus but long filaments can be seen all around it. Image Credit: I. Heywood, SARAO.

Achieving the precision necessary for this image was only possible thanks to the power of South African Radio Astronomy Observatory (SARAO)’s MeerKAT and over 200 hours of observations.

The final image of the center of the Milky Way, published in a different paper in The Astrophysical Journal, is a testament to the hard work and time necessary to study this crucial region of our galaxy.  

“I’ve spent a lot of time looking at this image in the process of working on it, and I never get tired of it,” the lead author of the second paper Ian Heywood, from Oxford University, explained.

“When I show this image to people who might be new to radio astronomy, or otherwise unfamiliar with it, I always try to emphasize that radio imaging hasn’t always been this way, and what a leap forward MeerKAT really is in terms of its capabilities. It’s been a true privilege to work over the years with colleagues from SARAO who built this fantastic telescope.”

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