Mysterious dashes revealed in Milky Way's center
Hundreds of horizontal filaments point toward our central supermassive
black hole

Date:
June 2, 2023
Source:
Northwestern University
Summary:
In the early 1980s, astronomers discovered gigantic, one-dimensional
filaments dangling vertically near Sagittarius A*, our galaxy's
central supermassive black hole. Now, astronomers have discovered a
new population of filaments -- but these threads are much shorter
and lie horizontally or radially, spreading out like spokes on a
wheel from the black hole.


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FULL STORY ==========================================================================
An international team of astrophysicists has discovered something wholly
new, hidden in the center of the Milky Way galaxy.

In the early 1980s, Northwestern University's Farhad Yusef-Zadeh
discovered gigantic, one-dimensional filaments dangling vertically
near Sagittarius A*, our galaxy's central supermassive black hole. Now, Yusef-Zadeh and his collaborators have discovered a new population of
filaments -- but these threads are much shorter and lie horizontally or radially, spreading out like spokes on a wheel from the black hole.

Although the two populations of filaments share several similarities,
Yusef- Zadeh assumes they have different origins. While the vertical
filaments sweep through the galaxy, towering up to 150 light-years high,
the horizontal filaments look more like the dots and dashes of Morse code, punctuating only one side of Sagittarius A*.

The study will be published on Friday (June 2) 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," Yusef-Zadeh
said. "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."
An expert in radio astronomy, Yusef-Zadeh is a professor of physics and astronomy at Northwestern's Weinberg College of Arts and Sciences and
member of CIERA.

Decades in the making The new discovery may come as a surprise, but
Yusef-Zadeh is no stranger to uncovering mysteries at the center of
our galaxy, located 25,000 light-years from Earth. The latest study
builds on four decades of his research. After first discovering the
vertical filaments in 1984 with Mark Morris and Don Chance, Yusef-Zadeh
along with Ian Heywood and their collaborators later uncovered two
gigantic radio-emitting bubbles near Sagittarius A*. Then, in a series
of publications in 2022, Yusef-Zadeh (in collaborations with Heywood,
Richard Arent and Mark Wardle) revealed nearly 1,000 vertical filaments,
which appeared in pairs and clusters, often stacked equally spaced or
side by side like strings on a harp.

Yusef-Zadeh credits the flood of new discoveries to enhanced radio
astronomy technology, particularly the South African Radio Astronomy Observatory's (SARAO) MeerKAT telescope. To pinpoint the filaments, Yusef-Zadeh's team used a technique to remove the background and smooth
the noise from MeerKAT images in order to isolate the filaments from surrounding structures.

"The new MeerKAT observations have been a game changer," he said. "The advancement of technology and dedicated observing time have given us new information. It's really a technical achievement from radio astronomers." Horizontal vs. vertical After studying the vertical filaments for decades, Yusef-Zadeh was shocked to uncover their horizontal counterparts,
which he estimates are about 6 million years old. "We have always been
thinking about vertical filaments and their origin," he said. "I'm used
to them being vertical. I never considered there might be others along
the plane." While both populations comprise one-dimensional filaments
that can be viewed with radio waves and appear to be tied to activities
in the galactic center, the similarities end there.

The vertical filaments are perpendicular to the galactic plane;
the horizontal filaments are parallel to the plane but point radially
toward the center of the galaxy where the black hole lies. The vertical filaments are magnetic and relativistic; the horizontal filaments appear
to emit thermal radiation. The vertical filaments encompass particles
moving at speeds near the speed of light; the horizontal filaments
appear to accelerate thermal material in a molecular cloud. There are
several hundred vertical filaments and just a few hundred horizontal
filaments. And the vertical filaments, which measure up to 150 light-years high, far surpass the size of the horizontal filaments, which measure
just 5 to 10 light-years in length. The vertical filaments also adorn
space around the nucleus of the galaxy; the horizontal filaments appear
to spread out to only one side, pointing 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 said.

'Our work is never complete' The new discovery is filled with unknowns,
and Yusef-Zadeh's work to unravel its mysteries has just begun. For now,
he can only consider a plausible explanation about the new population's mechanisms and origins.

"We think they must have originated with some kind of outflow from an
activity that happened a few million years ago," Yusef-Zadeh said. "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." The study, "The population of the galactic center filaments: Position angle distribution reveal a degree-scale collimated outflow
from Sgr A* along the galactic plane," was supported by NASA (award
number 80GSFC21M0002). The SARAO is a facility of the National Research Foundation, an agency of the Department of Science and Innovation.

* RELATED_TOPICS
o Space_&_Time
# Galaxies # Black_Holes # Astronomy # Astrophysics #
Space_Telescopes # Space_Exploration # Cosmic_Rays # Sun
* RELATED_TERMS
o Spitzer_space_telescope o Holographic_Universe o Black_hole
o Uranus'_natural_satellites o Extrasolar_planet o Galaxy o
Andromeda_Galaxy o Large-scale_structure_of_the_cosmos

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


========================================================================== Related Multimedia:
* MeerKAT_image_with_short_filaments ========================================================================== Journal Reference:
1. F. Yusef-Zadeh, R. G. Arendt, M. Wardle, I. Heywood. The
Population of
the Galactic Center Filaments: Position Angle Distribution Reveals
a Degree-scale Collimated Outflow from Sgr A* along the Galactic
Plane. The Astrophysical Journal Letters, 2023; 949 (2): L31 DOI:
10.3847/2041-8213/ acd54b ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230602115040.htm

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