Using the MeerKAT radio telescope, astronomers have obtained the clearest images of mysterious ‘strange radio circles’ (ORCs), offering unprecedented insight into these gigantic cosmic structures spanning regarding a million light-years .
gigantic structures
Circular prominences that cannot be explained by known objects or phenomena, strange radio circles are currently considered astronomical anomalies. It turns out that the first of these was only discovered in September 2019, and only five have been confirmed so far.
To make matters worse, these structures also exhibit low luminosity and do not show up in optical, infrared, or radiological wavelengths, so astronomers were initially unaware of whether they were huge and distant, or smaller and located at within our own galaxy.
More recent observations have made it possible to specify their size as well as the distance at which they were found, confirming the first hypothesis: with a diameter of approximately one million light-years, the ORC are 16 times larger than the Milky Way and appear to shroud galaxies whose cores contain active supermassive black holes, which might provide clues to their origin.
For this new study published in the journal Monthly Notices of the Royal Astronomical Society, astronomers have taken a closer look at the very first ORC discovered, using the South African radio telescope MeerKAT. With unprecedented definition, the resulting images revealed a complex structure containing multiple inner circles, and enabled the team to produce maps of the polarization and spectral index of the radiation.
Three potential “culprits”
With all this new data, the researchers were able to propose three main hypotheses regarding the origin of the ORC. These might be the remnants of huge explosions, possibly caused by the merger of two supermassive black holes, circular jets of energetic particles emanating from the galaxy’s core, or shock waves linked to the formation of new stars.
If radio telescopes MeerKAT and ASKAP will continue to collect data in order to shed full light on the nature of ORCthings should pick up speed in the second half of the decade, with the commissioning of the SKA (Square Kilometer Array).
