Dubbed “Kathryn’s Wheel” after the famous firework it resembles and after the wife of the paper’s second author. Such systems are very rare and arise from “bulls-eye” collisions between 2 galaxies of similar mass. Shockwaves from the collision compress reservoirs of gas in each galaxy and trigger the formation of new stars. This creates a spectacular ring of intense emission, and lights up the system like a Catherine wheel firework on bonfire night.
Galaxies grow through collisions but it is rare to catch one in the process, and extremely rare to see a bull’s-eye collision in progress. Fewer than 20 systems with complete rings are known. This occurred in the constellation of Ara (the Altar).
Kathryn’s Wheel was discovered during a special wide field survey of the Southern Milky Way undert...
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