Wednesday, May 18, 2022

Milky Way’s turbulent center has nearly 1,000 mysterious strands

‘A watershed in furthering our understanding of these structures,’ scientists say.

In the 1980s, Northwestern University‘s Farhad Yusef-Zadeh discovered highly organized, magnetic filaments in the Milky Way’s center. These filaments consist of cosmic-ray electrons orbiting the magnetic field at close to the speed of light.

However, their origin remains unknown.

A new image of the Milky Way’s center, taken by SARAO’s MeerKAT telescope, revealed almost 1,000 mysterious strands inexplicably dangling in space. These strands are in pairs and clusters, often stacked equally spaced, side by side like strings on a harp.

Along with strands, the image also revealed radio emissions from numerous phenomena, including outbursting stars, stellar nurseries, and new supernova remnants.

Scientists combined a mosaic of 20 separate observations- from SARAO’s MeerKAT telescope- of different sections of the sky toward the center of the Milky Way galaxy.

Yusef-Zadeh, the paper’s lead author, said, “We have studied individual filaments for a long time with a myopic view. Now, we finally see the big picture — a panoramic view filled with an abundance of filaments. 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.”

Oxford University astrophysicist Ian Heywood said, “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. When I show this image to people who might be new to radio astronomy or otherwise unfamiliar with it, I try to emphasize that radio imaging hasn’t always been this way and what a leap forward MeerKAT 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.”

Scientists later used a technique to remove the background from the main image. They wanted to separate the strands from the surrounding structures. And guess what, the resulting image was astonishing!

Heywood said, “It’s like modern art. These images are so beautiful and rich, and the mystery of it all makes it even more interesting.”

Many mysteries are surrounding these strands remains unsolved. In this new study, scientists specifically explored the filaments’ magnetic fields and the role of cosmic rays in illuminating the magnetic fields.

The difference in the radiation from the strands is different from that of the newly uncovered supernova remnant. It indicates that the phenomena have different origins.

Scientists found that the filaments are more likely related to the past activity of the Milky Way’s central supermassive black hole instead of coordinated bursts of supernovae. The filaments also could be related to enormous, radio-emitting bubbles.

Yusef-Zadeh said“This is the first time we have been able to study statistical characteristics of the filaments. By studying statistics, we can learn more about the properties of these unusual sources.”

“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. We can find the strength of magnetic fields, their lengths, their orientations, and the spectrum of radiation.”

“These filaments resemble the regular spacing in solar loops. 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.”

It remains unclear whether these filaments move or change over time. They also want to determine what causes the electrons to accelerate at such incredible speeds.

The team is currently identifying and cataloging each filament. Unraveling its properties could give the astrophysics community more clues into the filaments’ elusive nature.

Journal Reference:

  1. F. Yusef-Zadeh et al. Statistical Properties of the Population of the Galactic Center Filaments: The Spectral Index and Equipartition Magnetic Field. arXiv:2201.10552

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