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EI2GYB > ASTRO 18.10.25 10:05l 77 Lines 4471 Bytes #23 (0) @ WW
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Subj: The Hidden Rings of the Milky Way
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The Hidden Rings of the Milky Way
Radio astronomy opens a window onto the invisible universe. While our eyes can
detect visible light, countless objects in space emit radiation at much longer
wavelengths, in the radio portion of the electromagnetic spectrum. Where
visible light gets blocked by interstellar dust, radio waves pass through
unrestricted revealing objects that remain completely invisible to traditional
telescopes. Radio telescopes detect these waves, revealing phenomena that
optical telescopes simply cannot see. Radio waves also penetrate Earth's
atmosphere far more easily than many other wavelengths, making ground-based
radio observatories incredibly effective tools for exploring the universe.
MeerKAT is one such radio telescope, although it's actually a network of 64
antennas spread across eight kilometres of South Africa. Operating at 1.3 GHz,
it picked up previously undiscovered ring shaped structures during a survey of
the Galactic Plane. What makes these rings particularly fascinating is their
sheer diversity. About 40 percent contain isolated infrared sources at their
centres, while roughly half show extended structures visible in mid or far
infrared wavelengths. Surprisingly perhaps, several rings appear only in radio
observations with no counterpart at any other wavelength. Nearly one in five
features a central radio point source, suggestion there may be ongoing stellar
activity within.
The origins of these mysterious circles span the full spectrum of stellar
evolution. Some are likely planetary nebulae, the gaseous and dusty remains of
dying stars. Others may be expanding shells of material from stellar
explosions, or nova shells from less violent stellar outbursts. The researchers
also suspect that many rings originate from evolved massive stars like
Wolf-Rayet stars and luminous blue variables, whose powerful stellar winds
blast away their outer layers.
Beyond their stellar origins, some rings might have more exotic explanations. A
handful could be distant galaxies warped by gravitational lensing, or even
examples of odd radio circles, a newly discovered class of astronomical object
whose nature remains well and truly up for discussion. The team did manage
however to propose tentative classifications for nearly 60 percent of their
sample by cross referencing multiple wavelength observations and existing
astronomical catalogues. Definitive answers on their origins thought will
require follow up observations with even higher resolution instruments.
These discoveries highlight how much remains unknown about our own Galaxy's
population. Many of these objects had never been catalogued before, suggesting
that radio surveys with MeerKAT and similar next generation instruments are
revealing populations of celestial objects that previous surveys simply
couldn't detect. Each ring tells a story about stellar evolution, death, and
the complex processes shaping our Galaxy, waiting for astronomers to decode its
message.
Source : MeerKAT discovery of 164 compact radio rings toward the Galactic Plane
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