Scientists Think They’ve Discovered Where ‘Weird Radio Circles’ Come From: ScienceAlert
Over the past five years, astronomers have discovered a new type of astronomical phenomenon that exists on vast scales – larger than entire galaxies. They’re called ORCs (odd radio circles) and they look like giant rings of radio waves expanding like a shock wave.
Until now, ORCs had never been observed at any wavelength other than radio, but according to a new paper released on April 30, 2024, astronomers have captured X-rays associated with an ORC for the first time.
The discovery offers some new clues about what might be behind the creation of an ORC.
While many astronomical events, such as supernova explosions, can leave circular traces, ORCs seem to require a different explanation.
“The power required to produce such an expansive radio emission is very strong,” said Esra Bulbul, lead author of the new paper. “Some simulations can reproduce their shapes, but not their intensity. No simulations explain how to create ORCs.”
ORCs can be challenging to study, in part because they are generally only visible at radio wavelengths. They have not previously been associated with X-ray or infrared emissions, nor has there been any sign of them at optical wavelengths.
ORCs sometimes circle a visible galaxy, but not always (eight have been discovered to date around known elliptical galaxies).
Using ESA’s XMM-Newton telescope, Bulbul and his team observed one of the closest known ORCs, an object called Cloverleaf, and found a striking X-ray component in the object.
“This is the first time anyone has seen X-ray emission associated with an ORC,” Bulbul said. “It was the missing key to unlock the secret of the formation of Clover.”
Cloverleaf X-rays show gas that has been heated and excited by some process. In this case, X-ray emissions reveal two groups of galaxies (totaling about a dozen galaxies in total) that have begun to merge within Cloverleaf, heating the gas to 15 million degrees Fahrenheit.
Chaotic galaxy mergers are interesting, but they can’t explain Cloverleaf on their own. Galaxy mergers happen throughout the universe, while ORCs are a rare phenomenon. There’s something unique going on to create something like Cloverleaf.
“Fusions form the backbone of structure formation, but there is something special about this system that triggers radio emissions,” Bulbul said. “We can’t say at this point what it is, so we need more and deeper data, both from radio and X-ray telescopes.”
That doesn’t mean astronomers don’t have guesses.
“A fascinating idea for the powerful radio signal is that resident supermassive black holes have experienced episodes of extreme activity in the past, and the remaining electrons from that ancient activity have been reaccelerated by this merger event,” said Kim Weaver, project scientist at the NASA for XMM. -Newton.
In other words, ORCs like Cloverleaf may require a two-part origin story – powerful emissions from active supermassive black holes, followed by shockwaves from galaxy mergers that give those emissions a second boost.
This article was originally published by Universe Today. Read the original article.
