G305.4–2.2 is a supernova remnant located at a distance of 2.3 kpc with a rare circular symmetry in shape, nicknamed Teleios (Greek: τέλειος "perfect"). It has a radius of 3.3 parsecs. It is one of the most circular known supernova remnants. The age of G305.4-2.2 is not known with much precision with it either being young and under 1000 years old or an older remnant being over 10,000 years old.
It was identified in the radio-continuum images of the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe by a group of astronomers led by Miroslav D. Filipović of Western Sydney University.Perfect symmetry: Astronomers find unusual supernova remnant Mykyta Lytvynov, Universe (magazine), May 16, 2025Observations detect a perfectly shaped supernova remnant Tomasz Nowakowski, Phys.org, May 15, 2025
References
See also List of supernovae Supernova Lists of astronomical objects List of supernova remnants