2023年10月03日:MyCn 18：沙漏星云-（MyCn 18: The Engraved Hourglass Planetary Nebula）--原图下载
Image Credit & Copyright: NASA, ESA, Hubble, HLA;Processing & Copyright: Harshwardhan Pathak
说明: 你看见沙漏结构了吗？或者它在看你？如你想像力够用的话，MyCn 18的众多环状结构叠成一个沙漏，而沙漏孔形似一只眼睛。不论如何，位于这个形似沙漏的行星状星云内的中心星，来日已不多了。当类太阳恒星耗尽核燃料之后，它会抛出外层的气壳，经历这种短暂且美丽的恒星生命终结阶段，而其核心则会成为一颗逐渐冷却变暗的白矮星。在1995年，天文学家用哈伯太空望远镜，针对行星状星云拍摄了一系列影像，包括成为上面这幅影像主题的这团星云。在影像中，可以看见纤细的多环状辉光（氮为红、氢绿和氧蓝）所构成的纤薄沙漏管面。这种空前清晰的哈伯望远镜影像，所清楚呈现的云气抛射过程之细节，将有助于解开像MyCn 18这种行星状星云的複杂形状和对称性等神祕待解的难题。
原文：
Image Credit & Copyright: NASA, ESA, Hubble, HLA;Processing & Copyright: Harshwardhan Pathak
Explanation: Do you see the hourglass shape -- or does it see you? If you can picture it, the rings of MyCn 18 trace the outline of an hourglass -- although one with an unusual eye in its center. Either way, the sands of time are running out for the central starof this hourglass-shapedplanetary nebula.With its nuclear fuelexhausted, this brief, spectacular, closing phase of a Sun-like star's life occurs as its outer layers are ejected - itscore becoming a cooling, fadingwhite dwarf.In 1995, astronomers used theHubble Space Telescope(HST) to make a series ofimages of planetary nebulae, including the one featured here. Pictured, delicate rings of colorful glowing gas(nitrogen-red,hydrogen-green, andoxygen-blue) outline the tenuous walls of thehourglass.The unprecedented sharpness of the Hubble images has revealedsurprising details of the nebula ejection process that are helping to resolvethe outstanding mysteriesof the complex shapes and symmetries of planetary nebulas like MyCn 18.
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