Astronomers capture detailed insight into a mysterious new space phenomenon

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Astronomers just gave us our best picture yet of the mysterious rings in space called Odd Radio Circles, or ORCs for short. The image, compiled from data from South Africa’s MeerKAT radio observatory, gives a much more accurate look at a strange cosmic phenomenon that was only discovered last year.

The latest look at ORCs, published in Royal Astronomical Society Monthly Notices uses the more powerful MeerKAT telescope to zoom in on one in particular. The resulting image gives a much more detailed look at the ORC and allows astronomers to see some of the intricate structures inside. The ORC, which surrounds an elliptical galaxy, has what appear to be multiple rings within the main structure, and some regions are brighter than others. This new information could give us clues as to how ORCs form and what they are made of.

ORCs aren’t the hobbit-hunting beasts you might think – the acronym is actually quite accurate. ORCs are huge, circular-looking clouds a million light years in diameter that emit only radio waves – the lowest frequency type of electromagnetic radiation.

On the left, a previous image of the ORC1 object taken at the EMU observatory, while the right shows the MeerKAT image. The EMU team, using ASKAP and MeerKAT radio continuum data

“We know that ORCs are rings of faint radio emissions surrounding a galaxy with a very active black hole at its center, but we don’t yet know what causes them, or why they are so rare,” said Ray Norris. , professor at Western Sydney. University and co-author of the article, said in a press release.

Their visibility in the radio spectrum is one of the strangest things about these giant rings. Astronomers have found other large, circular things in space that look broadly like ORCs, but most of them can be seen in multiple wavelengths, including gamma rays, visible light and infrared . The Fermi Bubbles that extend from the center of our own Milky Way, for example, and which could be the remnants of massive jets from our galaxy’s central black hole, can be seen in both gamma rays and radio waves. .

But ORCs are completely invisible unless you search for them with a radio telescope. Perhaps that’s why astronomers have only seen five so far. ORCs first appeared in data from a large radio survey of the sky – the Australian Square Kilometer Array Pathfinder (ASKAP) Telescope’s Evolutionary Map of the Universe survey.

The new images are already revealing some of the secrets of these objects. What appears to us to be a flat ring could actually be a three-dimensional sphere, astronomers say. This could represent the shock wave of an ancient cataclysmic collision in the galaxy, such as that of the merger of two supermassive black holes. Such an event would blow a superheated cloud of debris and gas outward, which would be visible for millions of years.

ORCs could also come from a galaxy that forms a lot of stars, a so-called starburst galaxy. Star formation generates powerful stellar winds that sweep outward and can form bubbles. The ORCs could be the terminal shock, essentially the point at which the bubble stops, of these winds.

MeerKAT data on ORC1 overlaid with Dark Energy Survey observations of the same area. Jayanne English (U. Manitoba)

Yet another theory holds that ORCs are not spheres at all, but rather the tips of massive galactic jets from radio galaxies seen end to end. Supermassive black holes at the centers of galaxies emit streams of particles from their centers as they suck in material, and some of that material is ejected in huge jets that can span millions of years. -light in space. Radio galaxies emit most of their radiation as radio waves, and ORCs could be just the remnants of these galactic jets.

In a more outrageous take, some researchers have suggested that ORCs might even represent the throat of a wormhole, a theoretical shortcut through spacetime. The jury on that assumption is definitely still out, however.

While only five ORCs have been reported in scientific papers, scientists note that a few other candidate ORCs are currently under investigation. With more examples to examine and hopefully more detailed data to come, we may soon know more about these huge rings in the sky.

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