March 30, 2022
The night sky on your birthday is never quite the same twice — the planets shift, the constellations drift, the Moon wears a different phase.
Animation: Odd Radio Circles
Birthday · March 30, 2022
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APOD published March 30, 2022 · Video still. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
What do you call a cosmic puzzle that no one expected to see? In this case, Odd Radio Circles, aka ORCs. ORC-1 typifies the enigmatic five objects, only visible at radio frequencies, that were serendipitously discovered in 2019 using the new Australian SKA Pathfinder radio array. The final image in the featured video uses 2021 data from the South African MeerKAT array to reveal more detail. The radio data, assigned turquoise colors, are combined with a Dark Energy Survey optical/IR map. The animated artist’s illustration explores just one idea about the ORCs’ origins. If two supermassive black holes merge in the center of a galaxy, the associated shockwaves could generate rings of radio radiation. These grow to fill the video frame. The video zooms out so the expansion the ORC can be tracked until it is about a million light-years across. Fortunately, the up-coming Square Kilometer Array can help test this and other promising scenarios.