Astronomers uncover mysterious ‘Ghosts’ of the radio universe – The Tribune-OxBig News Network

Radio astronomers have discovered a series of faint, ghostly circular objects in space using advanced radio telescopes such as the Australian Square Kilometre Array Pathfinder (ASKAP) and MeerKAT in South Africa. These cutting-edge telescopes, designed to detect radio signals rather than visible light, are unveiling an unseen universe filled with mysterious cosmic structures.

The extraordinary sensitivity of these telescopes is revealing a “low surface brightness universe”, consisting of extremely faint radio sources that had never been observed before. Many of these discoveries come from the Evolutionary Map of the Universe (EMU) survey, a large-scale sky-mapping project using ASKAP, which is delivering the most detailed radio atlas of the southern hemisphere.

Among the recent discoveries is Kýklos, a ghostly ring, and WR16, both surrounding rare and massive Wolf-Rayet stars—a late stage in the life cycle of massive stars. As these stars burn through their fuel, they become unstable and eject layers of gas, forming nebulous circular structures. The expelled material expands symmetrically in all directions, creating the distinct circular shapes seen in radio observations.

Several newly discovered objects—Stingray 1, Perun, Ancora, and Unicycle—are supernova remnants, the aftermath of massive stellar explosions. When a star collapses under its own gravity, it releases an immense burst of energy, sending shockwaves outward. These expanding shells of stellar debris appear as striking circular formations.

A particularly intriguing supernova remnant, named Teleios (from the Greek “perfect”), stands out for its near-perfect symmetry. Unlike most remnants, which become distorted over time due to interactions with surrounding interstellar material, Teleios has remained untouched, providing rare insights into the physics of supernova explosions.

Another spectacular find is Diprotodon, one of the largest objects ever observed in the sky. Measuring nearly six times larger than the Moon, this remnant has only now been fully detected thanks to ASKAP’s sensitivity. The name Diprotodon was inspired by an extinct Australian megafauna species, a giant wombat-like creature, due to its vast size. The internal structure of this remnant reveals complex interactions with its environment, with different sections of the expanding shell colliding with interstellar clouds.

Another fascinating object, Lagotis, challenges previous classifications of cosmic structures. Originally identified as VdB-80, a reflection nebula within the Milky Way, new ASKAP data has revealed an additional structure—an HII region (a cloud of ionized hydrogen) surrounding the same stellar center. This discovery suggests that the nebula is actively interacting with a molecular cloud, much like a burrowing motion. This behavior inspired the name Lagotis, after the Australian greater bilby (Macrotis lagotis), an animal known for its digging nature.

ASKAP and MeerKAT are also shedding light on objects beyond our galaxy, including a class of mysterious radio ring galaxies. While these galaxies appear as normal disks in visible light, their radio signals reveal enormous rings, potentially caused by powerful supernova-driven shockwaves that have cleared the central regions of gas. However, the exact mechanism behind these structures remains uncertain, prompting further research.

One of the most puzzling discoveries is LMC-ORC, an Odd Radio Circle (ORC)—a newly identified class of objects with unknown origins. Only detectable in radio wavelengths, ORCs are among the most enigmatic findings in modern astronomy. Their formation mechanisms are still unclear, but ongoing studies are expected to shed light on their nature.

MeerKAT and ASKAP are merely the precursors to an even more powerful project—the Square Kilometre Array (SKA), an international collaborative effort that will revolutionize radio astronomy. The SKA will significantly enhance our ability to detect low surface brightness objects and uncover even more previously unknown cosmic structures.