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An international team of astronomers reports the discovery of a new supernova remnant that showcases a remarkable circular symmetry in shape. The detection of the remnant, dubbed "Teleios," is in a research paper published May 7 on the arXiv preprint server.

Supernova remnants (SNRs) are the remains of a supernova explosion, seen as diffuse, expanding structures. Observations show that SNRs harbor ejected material expanding from the supernova explosion. They also contain other interstellar material that has been swept up by the passage of the shockwave from the exploded star.

Recently, a group of astronomers led by Miroslav D. Filipović of Western Sydney University in Australia, has serendipitously detected a new supernova remnant, which received the designation G305.4–2.2. The newfound SNR was identified in the radio-continuum images of the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU).

According to the paper, G305.4–2.2 exhibits an almost perfectly circular shape; therefore, the astronomers nicknamed it "Teleios," which means "perfect" in Greek. The observations suggest that Teleios is located at a distance of 7,170 or 25,100 light years away, which corresponds to a diameter of 45.6 or 156.5 light years, respectively.

The astronomers underlined that the exceptional circularity of Teleios is unusual for SNRs, as only a few remnants exhibit similar morphology, like SNR J0624–6948, SN1987A, or MC SNR J0509–6731.

The study found some extended radio emission inside the southeastern edge of Teleios's shell. This suggests that at least some parts of this region might be affected by the interaction of Teleios with local interstellar medium (ISM) structures.

Furthermore, it was found that Teleios has a steep spectral index of -0.6, which is expected for somewhat young or very old SNRs. This spectral index, combined with the measured angular size of Teleios, points to a very low surface brightness.

To explain the origin of Teleios, the authors of the paper consider a few scenarios. According to the authors of the study, the most plausible one is a Type Ia supernova that was formed below the galactic plane.

"While we deem the Type Ia scenario the most likely, we note that no direct evidence is available to definitively confirm any scenario and new sensitive and high-resolution observations of this object are needed," the researchers concluded.

Summing up the results, the scientists propose future high-resolution multi-frequency observations of Teleios. Such observations could determine a possible expansion velocity, which could more accurately determine the properties of this remnant.

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