M27: 肯定不是彗星

2024年10月5日

M27: Not a Comet
Image Credit & Copyright: Francesco Sferlazza, Franco Sgueglia

Explanation: While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things encountered during his telescopic expeditions that were definitely not comets. This is number 27 on his now famous not-a-comet list. In fact, 21st century astronomers would identify it as a planetary nebula, but it’s not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star’s outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star’s intense but invisible ultraviolet light. Known by the popular name of the Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the constellation Vulpecula. This impressive color image highlights details within the well-studied central region and fainter, seldom imaged features in the nebula’s outer halo.

Tomorrow’s picture: a comet’s tale

M27: 肯定不是彗星
影像提供与版权: Francesco Sferlazza, Franco Sgueglia

说明: 在18世纪的法国夜空搜寻彗星时，天文学家查尔斯·梅西耶用心的编录了一本肯定不是彗星的天体名册，而上图就是这本著名非彗星星表的第27号天体。21世纪的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。梅西耶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，会辐射出可见光，形成了这种称为行星状星云的天体。这团俗称为哑铃星云的美丽对称星际云气，位于狐狸座方向，离我们约有1,200光年远，宽度则超过2.5光年。这幅精采的组合彩色影像，除了清楚呈现常受到探索研究的中心区之外，也记录了较暗、鲜少有影像记录的外晕之结构。

明日的图片: a magnificent tale