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Thor's Helmet in H-Alpha



影像版權與提供: Don Goldman

Explanation:
      Near picture center, the helmet-shaped structure with wing-like appendages is popularly called Thor's Helmet. Cataloged as NGC 2359, the striking nebula is located about 15,000 light-years away in the constellation Canis Major. The helmet is actually more like a cosmic bubble, blown as the wind from the bright, massive star near the bubble's center sweeps through the surrounding molecular cloud. Known as a Wolf-Rayet star, the energetic star is a blue giant thought to be in a brief, pre-supernova stage of evolution. The remarkable color composite combines broad and narrow band images - including a deep exposure recorded with an H-alpha filter. The H-alpha image traces the light from the region's glowing atomic hydrogen gas. Heroically sized even for a Norse god, this Thor's Helmet is about 30 light-years across.

說明:
      靠近影像中央，這個具有側翼的頭盔形結構被稱為是雷神的頭盔 (Thor's Helmet)。編號為NGC 2359的這團星雲位在大犬座內，離我們約有一萬五千年遠，它實際上較像是一個宇宙泡泡，是泡泡中心明亮大質量恆星之恆星風在周圍分子雲氣所吹出的結構。這顆藍巨星是顆沃夫-瑞葉型恆星，一般認為是處在恆星演化超新星階段前的短暫時期。這幅精彩的彩色合成影像，結合了寬波段和窄波段影像，其中包括一幅H-alpha濾鏡的長時間曝光影像；氫-阿爾發影像呈現了來自原子氫所發出的輝光。就以北歐神話神祇的標準來說，跨度大約是三十光年的雷神頭盔也實在是很巨大。

資料來源: Scientific American
               Department of Physics, NCKU