Nearby stellar bubble reframes a 40-year Milky Way center mystery
A radio feature long thought to tower over the Milky Way’s center is revealed to be a foreground, closed shell of ionized hydrogen about 6,520 light-years away and 115 light-years across. Optical spectroscopy across the structure shows coherent gas motion and excitation by young stars (photoionisation), consistent with a normal H II region rather than a nuclear outflow from Sagittarius A*. Distance was estimated via dust reddening and 3D dust maps, aligning with 2024 work that placed the lobe in the foreground. While large-scale Milky Way structures like the Fermi bubbles remain, this finding highlights how line-of-sight overlap can mimic connections near the Galactic Center.
