Northern Cape astronomers discover new kind of astronomical object
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In 2019, astronomers discovered massive celestial structures known as Odd Radio Circles (ORCs), spanning hundreds of thousands of light-years.
With only 11 detected so far, theories speculated on their origin, from wormhole throats to remnants of black hole collisions.
A recent study, however, suggests these enigmatic circles are shells formed by powerful galactic winds resulting from exploding massive stars, providing a new lens into galactic evolution.
Discovered using Australia’s SKA Pathfinder telescope and South Africa’s MeerKAT telescope, ORCs had only been observed through radio waves.
MeerKAT, initially the Karoo Array Telescope, is a significant radio telescope situated in Meerkat National Park in the Northern Cape. Formed with 64 antennas, MeerKAT is a precursor to the Square Kilometre Array (SKA) Radio Telescope and aligns with SKA-mid technologies.
Launched in 2018, MeerKAT, along with HERA and two Australian telescopes, precedes the final SKA, which when completed, will be the largest radio telescope in the world, designed by local engineers and industries, just as MeerKAT was.
The telescope consists of 64 antennas of 13.5m diameter with cryogenic receivers, compounding the signals received across this vast area into a single image, like a giant compound eye.
The telescope supports diverse observing modes, including continuum imaging, pulsar timing, and transient searches, ensuring flexibility for researchers.
ORC 4, observable from Earth’s Northern Hemisphere, was studied using the W.M. Keck Observatory in Hawaii, revealing luminous heated gas in visible light.
ORC 4, linked to a starburst galaxy with a high rate of star formation, exhibited outflowing galactic winds.
These winds, driven by exploding stars, ejected gas from the galaxy, creating a forward-moving shockwave that formed the radio circle.
Simulations, led by study coauthor Cassandra Lochhaas, indicated that high-mass outflow rates and low-density surrounding gas are key factors in ORC formation.
The galactic winds blew for 200 million years before ceasing, shaping the radio circle over an estimated 750 million years.
ORCs serve as a unique tool to observe extreme galactic winds, aiding in understanding their frequency and life cycle.
Insights into galactic evolution, including the possibility of all massive galaxies going through an ORC phase, enrich our comprehension of celestial dynamics.
This groundbreaking research, detailed in the journal Nature, not only demystifies the origin of ORCs but opens new avenues for studying the impact of galactic winds on the evolution of galaxies.
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