这张迷人的望远镜照片中,是暗淡且令人难以捉摸的“水母星云”,它飘浮在双子座脚下的明亮恒星“钺”(双子座η)附近,中央偏左处明亮的辐射弧是水母的身体,向右倒悬的则是水母触须。实际上,这个大水母是泡状超新星遗迹 IC 443 中的一部分,是一颗大质量恒星爆炸后产生的碎片云,而爆炸闪光在 30000 年前就已到达地球。IC 443 和它的宇宙水生表亲“蟹状星云”一样,也包含有一颗中子星,它们是恒星核崩塌后的残留物。水母星云距离我们约 5000 光年,以这个距离推算,上图的跨度将达到 100 光年。
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Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic view. Drifting near bright star Eta Geminorum, at the foot of a celestial twin, the Jellyfish Nebula is seen dangling tentacles from the bright arcing ridge of emission left of center. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, IC 443 is known to harbor a neutron star, the remnant of the collapsed stellar core. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 100 light-years across.
每日天文一图(APOD)是美国宇航局天体物理学部每日定期发布的天文图片,并配有专业的简短解释,是小子时常光顾的地方,地址为:http://apod.nasa.gov/apod/。现将部分酷图转来并对原文解释做了翻译,英文及天文知识均有限,译错之处敬请各位指正。
秋天的麦兜 2013年1月9日 于济南。
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