Unlocking the secrets of the universe, researchers have discovered a hidden realm of circular structures through cosmic radio waves. From massive Wolf-Rayet stars to mysterious Odd Radio Circles, this uncharted territory is rewriting our understanding of the cosmos.
The vast expanse of space that radio astronomers explore is invisible to the naked eye and even most types of telescopes. However, thanks to recent advancements in radio observatories, scientists are uncovering an entire ‘low surface brightness universe’ teeming with circular curiosities.
This uncharted realm is made up of radio sources so faint they have never been seen before, each with their own unique physical properties. As researchers from Australia, led by Miroslav Filipovic from Western Sydney University, explain in an essay for The Conversation, ‘As we study the sky with telescopes that record radio signals rather than light, we end up seeing a lot of circles.’
Allowing astronomers to delve into this uncharted realm are the Australian Square Kilometer Array Pathfinder (ASKAP) and the South African MeerKAT radio telescope. These powerful instruments are continuously involved in performing surveys of the night sky, with ASKAP leading one called the Evolutionary Map of the Universe (EMU), launched in 2022.
Two of the most interesting objects discovered by this new generation of radio telescopes are stellar oddities known as Wolf-Rayet stars. Dubbed Kýklos and WR16, these massive celestial bodies are perhaps 25 times heavier than the Sun and near the end of their relatively brief lifespans.
Wolf-Rayet (WR) stars are massive, luminous stars that have exhausted their hydrogen fuel.
They are characterized by strong stellar winds and intense radiation.
WR stars are often found in binary systems and can be surrounded by circumstellar envelopes.
These stars are short-lived, with lifetimes ranging from 10,000 to 1 million years, depending on their mass.
Their spectra show emission lines of helium and nitrogen, which are indicative of 'their high surface temperatures and intense radiation.'
Radio imagery has also revealed a number of supernova remnants, or the sphere of gases and other material left behind after a massive star burns through its fuel, collapses under its own gravity, and epically explodes. The supernova remnant named Teleios is particularly significant, as it’s so perfect that nothing like it has ever been seen before.
The Teleios supernova remnant is a celestial object located in the Large Magellanic Cloud, a satellite galaxy of the Milky Way.
It is classified as a Type Ia supernova remnant, resulting from the explosion of a white dwarf star.
The remnant measures approximately 1.5 parsecs in diameter and is characterized by its symmetrical shape and high surface brightness.
Teleios was discovered in 2010 using the Chandra X-ray Observatory and the Hubble Space Telescope.
Most mysterious of all is the latest instance of a new class of cosmic objects called Odd Radio Circles (ORCs). These are unfathomably large, often imprisoning entire galaxies at their centers, with some being ten times as wide as the Milky Way.
An Odd Radio Circle is a type of astronomical phenomenon discovered in 2020.
These mysterious circles are observed as rings of radio emission, unlike any known astrophysical process.
They appear to be about 1-2 arcminutes in diameter and have no visible optical or infrared counterparts.
Researchers believe that these enigmatic structures could be the result of a massive explosion or an exotic type of neutron star.
Further investigation is needed to determine their origin and nature.
Tantalizingly, this is just the beginning of our exploration of the ‘low-surface brightness universe,’ according to Filipovic. The ASKAP and MeerKAT are just the prelude to the mother of all telescopes: the Square Kilometer Array, which will be the biggest radio observatory in history once completed.
