安魂曲超新星：目前为止已见到3次的超新星
2021年11月02日
SN Requiem: A Supernova Seen Three Times So Far
Image Credit: NASA, ESA, Hubble; Data: S. A. Rodney (U. South Carolina) et al.; Image Processing: J. DePasquale (STScI)
Explanation: We’ve seen this same supernova three times — when will we see it a fourth? When a distant star explodes in a supernova, we’re lucky if we see it even once. In the case of AT 2016jka (“SN Requiem”), because the exploding star happened to be lined up behind the center of a galaxy cluster (MACS J0138 in this case), a comparison of Hubble Space Telescope images demonstrate that we saw it three times. These three supernova images are highlighted in circles near the bottom of the left frame taken in 2016. On the right frame, taken in 2019, the circles are empty because all three images of the single supernova had faded. Computer modeling of the cluster lens, however, indicates that a fourth image of the same supernova should eventually appear in the upper circle on the right image. But when? The best models predict this will happen in 2037, but this date is uncertain by about two years because of ambiguities in the mass distribution of the cluster lens and the brightness history of the stellar explosion. With refined predictions and vigilant monitoring, Earthlings living 16 years from now may be able to catch this fourth image — and perhaps learn more about both galaxy clusters and supernovas at once.
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Tomorrow’s picture: Orange Horse and Flame
安魂曲超新星：目前为止已见到3次的超新星
影像提供: NASA, ESA, Hubble; 数据: S. A. Rodney (U. South Carolina) et al.; 影像处理: J. DePasquale (STScI)
说明: 同一颗超新星身影的已出现三次了，什么时候我们能见到第四次？当遥远恒星发生超新星爆炸时，我们得很走运才能见到1次它的影迹。不过以AT 2016jka（SN Requiem 安魂曲超新星）来说，因为它的前导爆炸恒星恰好位在星系团MACS J0138的核心后方，根据上面这幅哈勃望远镜对照图，我们共见到3次它的身影。在摄于2016年的左图里，空心圆标示出这3个位在图底附近的超新星身影。相较之下，在摄于2019年的右图里，这3个圆皆已全空，因为这颗超新星的3个影迹已然暗去。不过，这个星系团的引力透镜电脑模拟指出，这例超新星的第四个身影会出现在右图顶端的空心圆内。然而到底是何时？最佳的模拟预测，它应在2037年现身，不过因此星系团质量分布和恒星爆炸亮度的不确定性，发生的时日不确定性为2年。也就是说，以更精准的预测为指引并配合孜孜不倦的监测，16年后的地球住民或许能见到它的第四个身影，也或许能同时对星系团和超新星有更深入的了解。
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明日的图片: Orange Horse and Flame