Previous images of the Ring Nebula taken by visible-light telescopes usually showed just the inner glowing loop of gas around the star.
以前由可见光望远镜拍摄的星云环仅仅显示出其内部的环绕着恒星的炽热气体环。
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The Cygnus Loop appears as a faint ring of glowing gases about three degrees across (six times the diameter of the full moon), located in the northern constellation Cygnus the Swan.
天鹅座的Loop看起来是个由炽热气体形成的模糊光环(满月直径的6倍大小)，坐落在天鹅座星群的北方。
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Near the end of the expansion phase, the ring of plasma breaks open, and some of the plasma appears to escape the pull of the magnetic field loop.