Mysterious strands found at Milky Way’s center






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Milky Ways center is home to a number of unsolved mysteries including the recently discovered nearly 1,000 mysterious strands, inexplicably dangling in space.

The strands are visible in the unprecedented new telescope image wherein these strands are seen stretching up to 150 light years long. These one-dimensional strands (or filaments) are found in pairs and clusters, often stacked equally spaced, side by side like strings on a harp.

The observations at radio wavelengths were made by Northwestern University’s Farhad Yusef-Zadeh back in the early 1980s. The mystifying filaments, he found, comprise cosmic ray electrons gyrating the magnetic field at close to the speed of light. But their origin has remained an unsolved mystery ever since.

Now, the new image has exposed 10 times more filaments than previously discovered, enabling Yusef-Zadeh and his team to conduct statistical studies across a broad population of filaments for the first time. This information potentially could help them finally unravel the long-standing mystery.

The study was published online today by The Astrophysical Journal Letters.

Constructing the image

To construct the image with unprecedented clarity and detail, astronomers spent three years surveying the sky and analyzing data at the South African Radio Astronomy Observatory (SARAO). Using 200 hours of time on SARAO’s MeerKAT telescope, researchers pieced together a mosaic of 20 separate observations of different sections of the sky toward the center of the Milky Way galaxy, 25,000 light years from Earth.

The full image will be published in an additional, accompanying paper— led by Oxford University astrophysicist Ian Heywood and co-authored by Yusef-Zadeh — in a forthcoming issue of The Astrophysical Journal. Along with the filaments, the image captures radio emissions from numerous phenomena, including outbursting stars, stellar nurseries and new supernova remnants.

To view the filaments at a finer scale, Yusef-Zadeh’s team used a technique to remove the background from the main image in order to isolate the filaments from the surrounding structures. The resulting picture astounded him.

What we know

While many mysteries surrounding the filaments remain, Yusef-Zadeh has been able to piece together more of the puzzle. In their latest paper, he and his collaborators specifically explored the filaments’ magnetic fields and the role of cosmic rays in illuminating the magnetic fields.

The variation in radiation emitting from the filaments is very different from that of the newly uncovered supernova remnant, suggesting that the phenomena have different origins. It is more likely, the researchers found, that the filaments are related to past activity of the Milky Way’s central supermassive black hole rather than coordinated bursts of supernovae. The filaments also could be related to enormous, radio-emitting bubbles, which Yusef-Zadeh and collaborators discovered in 2019.

And, while Yusef-Zadeh already knew the filaments are magnetized, now he can say magnetic fields are amplified along the filaments, a primary characteristic all the filaments share.

What we don’t know

Among the remaining mysteries, Yusef-Zadeh is particularly puzzled by how structured the filaments appear. Filaments within clusters are separated from one another at perfectly equal distances — about the distance from Earth to the sun.

“They almost resemble the regular spacing in solar loops,” he 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.”

Yusef-Zadeh and his team also still don’t know whether the filaments move or change over time or what is causing the electrons to accelerate at such incredible speeds.

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