2019年08月29日:M27: 肯定不是彗星-（M27: Not a Comet）--原图下载
Image Credit &Copyright: Bob Franke
说明: 在18世纪的法国夜空搜索彗星时，天文学家梅西叶勤奋地编录了一个肯定不是彗星的天体名册，而这就是现在着名非彗星星表的第27号天体。而在21世纪，天文学家会将它分类为行星状星云，但是实际上它也不是行星，只是用小望远镜观测时，它具有类似行星的圆浑外观而已。梅西叶27(M27)是一个非常典型的发射星云，是类太阳恒星，在耗尽核心的燃料后所产生的。当恒星的外层被抛到太空中时，外层气壳里的原子，受到垂死恒星发出的强烈不可见紫外光之激发，而辐射出可见光，形成了这种称为行星状星云的天体。这团常称为哑铃星云的美丽对称星际云气，位在狐狸座内，离我们约有1,200光年远，宽度则超过2.5光年。这幅精采的彩色影像，除了呈现经常被探索研究的中心区之外，也清楚展现较暗、鲜少有影像记录的外晕。影像整合了宽波段滤镜数据，与及只透过氢和氧原子辐射的窄波段滤镜影像数据。
原文：
Image Credit &Copyright: Bob Franke
Explanation: While hunting for comets in the skies above 18th century France,astronomer Charles Messierdiligently kept a list of the thingshe encountered that were definitely not comets.This is number 27 on hisnowfamous not-a-comet list.In fact, 21st century astronomers would identify it as aplanetarynebula, but it's not a planet either, even though it mayappear round andplanet-like in a small telescope.Messier 27 (M27) is an excellent example of a gaseous emission nebulacreated as a sun-like star runs outof nuclear fuel in its core.The nebula forms as the star's outer layers are expelled intospace, with a visible glow generated by atoms excited by the dyingstar's intense but invisibleultraviolet light.Known by the popular name of theDumbbellNebula, the beautifullysymmetric interstellar gas cloud is over 2.5 light-years across andabout 1,200 light-years away in theconstellationVulpecula.This impressive color composite highlights details withinthe well-studied central region and fainter, seldom imagedfeatures in the nebula's outer halo.It incorporates broad and narrowbandimages recorded usingfilters sensitive to emission from hydrogen and oxygen atoms.
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