2019 October 25

The Ghosts of Cassiopeia
Image Credit & Copyright:
Tommaso Stella

Explanation: These bright rims and flowing shapes look ghostly on a cosmic scale. A telescopic view toward the constellation Cassiopeia, the colorful skyscape features swept-back, comet-shaped clouds IC 59 (left) and IC 63. About 600 light-years distant, the clouds aren’t actually ghosts. They are slowly disappearing though, under the influence of energetic radiation from hot,luminous star gamma Cas. Gamma Cas is physically located only 3 to 4 light-years from the nebulae, the bright star just above and left in the frame. 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 field of view spans over 1 degree or 10 light-years at the estimated distance of gamma Cas and friends.

Tommaso Stella

说明:这些具有明亮边缘和流体形状的天体在宇宙尺度上看起来像幽灵一样。这幅使用望远镜朝仙后座方向拍摄的天空影像呈现了后掠式彗星状星云IC 59(影像左侧)和IC 63。这些距离我们约600光年远的星云实际上并不是幽灵。然而,在炽热明亮的仙后γ型星的高能辐射影响下,它们正在慢慢消失。仙后γ型星距离星云只有3到4光年远,这颗明亮的恒星就位于影像的左上方。IC 63离仙后γ型星稍近,它所呈现的红色辉光是由恒星紫外辐射电离的氢原子与电子重新结合后发出的。IC 59离恒星较远,它呈现出相对较少的红色辉光,但更多是尘埃反射星光所发出的特有蓝光。以仙后γ型星和其周围天体的估计距离来计算,这片视野覆盖了超过1度或10光年的天区。

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