• Nearly 1,000 mysterious strands revealed

    From ScienceDaily@1:317/3 to All on Wed Feb 2 21:30:40 2022
    Nearly 1,000 mysterious strands revealed in Milky Way's center
    `A watershed in furthering our understanding of these structures,'
    researcher says

    Date:
    February 2, 2022
    Source:
    Northwestern University
    Summary:
    More than 35 years ago, a Northwestern professor discovered
    mysterious, gigantic magnetic filaments in the Milky Way galaxy's
    turbulent center.

    Now, armed with more advanced technology, he and his collaborators
    have uncovered nearly 1,000 of the strange structures.



    FULL STORY ==========================================================================
    An unprecedented new telescope image of the Milky Way galaxy's turbulent
    center has revealed nearly 1,000 mysterious strands, inexplicably dangling
    in space.


    ========================================================================== Stretching up to 150 light years long, the one-dimensional strands
    (or filaments) are found in pairs and clusters, often stacked equally
    spaced, side by side like strings on a harp. Using observations at radio wavelengths, Northwestern University's Farhad Yusef-Zadeh discovered the
    highly organized, magnetic filaments 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.

    "We have studied individual filaments for a long time with a myopic
    view," said Yusef-Zadeh, the paper's lead author. "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." Yusef-Zadeh is a professor of physics and astronomy at Northwestern's
    Weinberg College of Arts and Sciences and a member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA).



    ========================================================================== 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.

    "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," Heywood said. "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." 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.



    ========================================================================== "It's like modern art," he said. "These images are so beautiful and rich,
    and the mystery of it all makes it even more interesting." 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.

    "This is the first time we have been able to study statistical
    characteristics of the filaments," he said. "By studying the 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."
    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.

    "How do you accelerate electrons at close to the speed of light?" he
    asked.

    "One idea is there are some sources at the end of these filaments that
    are accelerating these particles." What's next Yusef-Zadeh and his
    team are currently identifying and cataloging each filament. The angle,
    curve, magnetic field, spectrum and intensity of each filament will be published in a future study. Understanding these properties will give
    the astrophysics community more clues into the filaments' elusive nature.

    The MeerKAT telescope, which launched in July 2018, will continue to
    unveil new secrets.

    "We're certainly one step closer to a fuller understanding," Yusef-Zadeh
    said.

    "But science is a series of progress on different levels. We're hoping to
    get to the bottom of it, but more observations and theoretical analyses
    are needed.

    A full understanding of complex objects takes time." The study,
    "Statistical properties of the population of the galactic center
    filaments: The spectral index and equipartition magnetic field," was
    supported by NASA and the National Science Foundation.

    ========================================================================== Story Source: Materials provided by Northwestern_University. Original
    written by Amanda Morris. Note: Content may be edited for style and
    length.


    ========================================================================== Journal Reference:
    1. F. Yusef-Zadeh, R. G. Arendt, M. Wardle, I. Heywood, W. Cotton, F.

    Camilo. Statistical Properties of the Population of the Galactic
    Center Filaments: the Spectral Index and Equipartition Magnetic
    Field. The Astrophysical Journal Letters, 2022; 925 (2): L18 DOI:
    10.3847/2041-8213/ ac4802 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/02/220202134652.htm

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