These new objects are only visible in radio wavelengths and are ring (circular) shaped, hence the acronym ORC (Odd Radio Circles). The 4 discovered are all off the galactic plane so are presumed not in the Milky Way. It is not known how far away they are. They span about 1 arcminute (one twentieth of the moon’s apparent width) and two have galaxies visible within the ring. No convincing expalanations yet – the leading contender may be shockwaves from some event. More are expected to be discovered as this particular radio survey continues (EMU).

Live Science article

Research paper