仙后座“策”与幽灵状星云

2023年10月28日

The Ghosts of Gamma Cas
Image Credit & Copyright: Guillaume Gruntz, Jean-François Bax

Explanation: Gamma Cassiopeiae shines high in northern autumn evening skies. It’s the brightest spiky star in this telescopic field of view toward the constellation Cassiopeia. Gamma Cas shares the ethereal-looking scene with ghostly interstellar clouds of gas and dust, IC 59 (top left) and IC 63. About 600 light-years distant, the clouds aren’t actually ghosts. They are slowly disappearing though, eroding under the influence of energetic radiation from hot and luminous gamma Cas. Gamma Cas is physically located only 3 to 4 light-years from the nebulae. Slightly closer to gamma Cas, IC 63 is dominated by red H-alpha light emitted as hydrogen atoms ionized by the star’s ultraviolet radiation recombine with electrons. Farther from the star, IC 59 shows proportionally less H-alpha emission but more of the characteristic blue tint of dust reflected star light. The cosmic stage spans over 1 degree or 10 light-years at the estimated distance of gamma Cas and friends.

Tomorrow’s picture: moon shadow

仙后座“策”与幽灵状星云
影像提供与版权: Guillaume Gruntz, Jean-François Bax

说明: 仙后座“策”（γ Cas）是高悬在北半球秋夜天空的亮星。在这幅远眺仙后座的望远镜影像里，最明亮的带芒恒星即为策星。这片缥缈视野里的策，有幽灵般的星际气体尘埃IC 59（左上）及IC 63为伴。这些离我们大约600光年远的星云，其实并不是幽灵。不过，在炽热明亮策星的高能辐射之照耀下，它们受到了侵蚀，倒是正在缓缓消散之中。在空间上，策与这些星云相去约3到4光年。较邻近策的IC 63，其醒目的泛红氢α辐射，是其内受到这颗恒星紫外光电离的氢原子与电子复合所发出的光。而离策较远的IC 59，氢α辐射也等比例弱化，但尘埃反射星光所产生的特征泛蓝色泽反而较鲜明。以策及其伙伴的估计距离来换算，这片宽约1度的宇宙视野，跨幅约有10光年。

明日的图片: moon shadow