Astronomers may have been solved the mystery of giant circles of radio waves that were first spotted in 2019 floating in the depths of space.
A team at the University of California San Diego found odd radio circles (ORCs) are formed by outflowing winds created by explosive events like a supernova.
Astronomers determined that when enough massive stars die and explode near each other, the force pushes the surrounding gas outward, creating outflowing winds at a speed of more than 1,200 miles per second.
The sheer force from the outflowing winds forms the shells that make up the radio wave circles, which can be more than 50,000 times the diameter of our Milky Way.
Astronomers may have solved the long-held mystery of giant circles of radio waves that appear hazy while floating in the depths of space
Astrophysics Alison Coil said: ‘These galaxies are really interesting. They occur when two big galaxies collide.
‘The merger pushes all the gas into a very small region, which causes an intense burst of star formation.
‘Massive stars burn out quickly, and when they die, they expel their gas as outflowing winds.’
To unravel the mystery, the team recreated outflowing galactic winds blowing for 200 million years before shutting off.
When the wind ceases, a forward-moving shock propelled high-temperature gas out of the galaxy and created a radio ring.
And then a reverse shock sent cooler gas flowing back into the galaxy.
A team at the University of California San Diego found odd radio circles (ORCs) are formed by outflowing winds created by explosive events like a supernova
The simulation was designed to play over the course of 750 million years, which the team said is about the estimated age of an ORC observed by astronomers in the past.
Astronomers discovered the radio wave circles using the Australian Square Kilometer Array Pathfinder (ASKAP) in 2019, but they were baffled by what they found.
It was such an unusual discovery that Coil and her team set out to discover how and why it formed.
Before the ASKAP telescope, astronomers had only observed ORCs through radio emissions but didn’t have access to any visual data.
It led to multiple theories about the phenomenon’s origins, including planetary nebulae, when cosmic gas and dust are shed from a dying star’s outer layers and black hole mergers.
The latter emits gravitational radiation when two black holes merge.
Both theories were discarded and replaced with the possibility that starburst galaxies created the ORCs.
Coil and her team used optical and infrared imaging data to determine that the stars within the ORC 4 galaxy were six billion years old.
Alison Coil and her team found that the force from outward winds from massive exploding stars created the ORCs
Astronomers used the ASKAP to capture images of ORCs that were previously only viewed through radio emissions
‘There was a burst of star formation in this galaxy,’ Coil said, ‘but it ended roughly a billion years ago.
‘It turns out the galaxies we’ve been studying have these high-mass outflow rates. They’re rare, but they do exist.
‘I really do think this points to ORCs originating from some kind of outflowing galactic winds.’
The ASKAP is the world’s fastest telescope, made up of 36 antennas, each 12 centimeters in diameter, and was created to detect hundreds of more galaxies than its predecessors to understand how galaxies form and evolve, including how Earth’s galaxy developed.
The telescope scans large portions of the sky at faint limits, enabling astronomers to view the ORCs that stretch across hundreds of kiloparsecs – equal to 3,260 light-years.
Coil said that ‘ORCs provide a way for us to ‘see’ the winds through radio data and spectroscopy.’
This means they could further determine how common the outflowing galactic winds are and the length of the wind life cycle, and will help astronomers learn more about the evolution of galaxies.
‘Do all massive galaxies go through an ORC phase? Do spiral galaxies turn elliptical when they are no longer forming stars?’ Coil questioned, adding: ‘I think there is a lot we can learn about ORCs and learn from ORCs.’
