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The Iris Nebula in a Field of Dust Image Credit & Copyright: FrancoSgueglia & Francesco Sferlazza Explanation: What blue flower grows in thisfield of dark interstellar dust? The Iris Nebula. The striking blue color ofthe Iris Nebula is created by light from the bright star SAO 19158 reflectingoff of a dense patch of normally dark dust. Not only is the star itself mostlyblue, but blue light from the star is preferentially reflected by the dust --the same effect that makes Earth\\\'s sky blue. The brown tint of the pervasivedust comes partly from photoluminescence -- dust converting ultravioletradiation to red light. Cataloged as NGC 7023, the Iris Nebula is studiedfrequently because of the unusual prevalence there of Polycyclic AromaticHydrocarbons (PAHs), complex molecules that are also released on Earth duringthe incomplete combustion of wood fires. The bright blue portion of the IrisNebula spans about six light years. The Iris Nebula, pictured here, lies about1300 light years distant and can be found with a small telescope toward theconstellation of Cepheus. 尘埃场内的鸢尾花星云 在这片黑暗星际尘埃场内绽放的蓝色花朵是什么？它是鸢尾花星云。鸢尾花星云之所以有引人注目的蓝色，是因为亮星SAO 19158的星光受到一片普通致密的黑暗尘埃反射所致。不仅这颗恒星本身看起来是蓝色的，它发出的蓝色星光也会优先被尘埃反射，地球上天空呈现蓝色也是这个道理。遍布各处尘埃的棕色辉光部分来自光激发光——尘埃将紫外辐射转化成红光。编号为 NGC 7023的鸢尾花星云因含有大量的多环芳香烃而经常成为天文学家的研究的目标，地球上的木材不完全燃烧时也会产生这种复杂分子。在这幅图像中，鸢尾花星云的亮蓝色区域跨度约6光年。鸢尾花星云距离地球约1300光年，用一台小型望远镜就能够在仙王座方向看到它。 参考文献： https://apod./apod/image/1808/IrisNebula_Sgueglia_2729.jpg 近期文章： Astronomy Picture of the Day——哈雷彗星的尘埃与银河 |
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