The Structured Tails of Comet NEOWISE
Image Credit & Copyright: Zixuan Lin (Beijing Normal U.)
Explanation: What is creating the structure in Comet NEOWISE’s tails? Of the two tails evident, the blue ion tail on the left points directly away from the Sun and is pushed out by the flowing and charged solar wind. Structure in the ion tail comes from different rates of expelled blue-glowing ions from the comet’s nucleus, as well as the always complex and continually changing structure of our Sun’s wind. Most unusual for Comet C/2020 F3 (NEOWISE), though, is the wavy structure of its dust tail. This dust tail is pushed out by sunlight, but curves as heavier dust particles are better able to resist this light pressure and continue along a solar orbit. Comet NEOWISE’s impressive dust-tail striations are not fully understood, as yet, but likely related to rotating streams of sun-reflecting grit liberated by ice melting on its 5-kilometer wide nucleus. The featured 40-image conglomerate, digitally enhanced, was captured three days ago through the dark skies of the Gobi Desert in Inner Mongolia, China. Comet NEOWISE will make it closest pass to the Earth tomorrow as it moves out from the Sun. The comet, already fading but still visible to the unaided eye, should fade more rapidly as it recedes from the Earth.
Tomorrow’s picture: open space
说明: NEOWISE彗星彗尾里的结构是怎么产生的？在它清楚可见的二道长尾里，左侧泛蓝的离子尾，在流泛带电的太阳风推送下，指向远离太阳的方向。离子尾里的结构，是因为彗核排放发蓝光的离子之速率不均，以及复杂的太阳风之风速不停变动所致。不过，NEOWISE彗星（C/2020 F3）最特殊的的是它波浪状的尘尾。尘尾源自被阳光光压推出的小碎片，因为这些尘埃微粒较重较能抵抗光压，因此形成散落在彗星绕日的轨道上的弯曲尘尾。 NEOWISE彗星壮观尘尾上的分层结构之成因，目前尚未完全厘清，不过可能和5公里宽彗核上的冰溶化时，释放出的反光砂砾流，因彗核转动而回旋喷洒有关。这幅组合40张数位强化照片的主题影像，是在3天前摄于中国．内蒙古．戈壁沙漠的幽暗星空下。在远离太阳的返程中，明天NEOWISE彗星将运行到最接近地球的位置。这颗已开始变暗的彗星，目前肉眼仍然可见，不过在远离地球后，将会快速变暗。
明日的图片: open space