2024-01-13 19:14:30
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An “odd radio circle” (ORC) recorded by the MeerKAT radio telescope (green object), the background comes from the Dark Energy Survey. © J. English (U. Manitoba)/EMU/MeerKAT/DES(CTIO)
Strange radio circles in the universe, known as ORCs, have long puzzled science. Now there seems to be an explanation.
San Diego – They were discovered for the first time in 2019: mysterious rings in space that are not visible in either the optical or infrared range. They also don’t emit any X-rays – only radio waves. That’s why they are called “odd radio circles” and are abbreviated as ORCs. To date, only a few of these unusual structures have been discovered and while there are some theories, an explanation for their existence is still missing. But now the mystery of the strange circles in the universe could be solved. The study was in the specialist journal Nature published.
A team of researchers led by Alison Coil from the University of California San Diego has found a possible explanation for the emergence of ORCs. The scientists focused on so-called “starburst” galaxies, i.e. galaxies in which an unusually high number of stars are formed. “These galaxies are really interesting,” Coil explains in one notice their university. “They are formed when two large galaxies collide. The merger squeezes all the gas into a very small region, resulting in an intense burst of star formation.”
ORCs appear to be formed by the galactic winds of dying stars
But that’s not all, as Coil goes on to say: Massive stars would burn out quickly, and when they died they would expel their gas as outflowing winds. According to the researcher, this process could lead to the strange radio circles: If enough stars explode at the same time in close proximity to each other, the explosion can push the gas out of the galaxy. The winds could reach speeds of up to 2000 kilometers per second – and give rise to the OCRs.
However, some prerequisites are necessary for this, explains Coil: “For this to work, you need a massive outflow, which means that a lot of material is ejected very quickly. And the surrounding gas outside the galaxy must have a low density, otherwise the shock will stop. These are the two key factors.”
Her research team found that the galaxies they studied had these high mass outflow rates, Coil explains, continuing: “They may be rare, but they do exist. I really think this suggests that ORCs come from some sort of outflowing galactic winds.” (tab)
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