SN安魂曲：一颗被发现三次的超新星
(原标题: SN Requiem: A Supernova Seen Three Times So Far)
2021-11-02
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我们已经三次看到同样的超新星了——什么时候我们会看到第四次呢？当一颗遥远的恒星以超新星的形式爆炸时，我们能看到一次就已经很幸运了。以AT 2016jka（“SN安魂曲”）为例，因为这颗爆炸的恒星恰好排在一个星系团（在这个例子中是MACS J0138）的中心后面，哈勃太空望远镜的图像对比表明，我们看到了它三次。这三颗超新星的图像在2016年拍摄的左图底部附近的圆圈中突出显示。在2019年拍摄的右图中，圆圈是空的，因为这颗超新星的三张照片都褪色了。然而，星系团透镜的计算机模型表明，同一颗超新星的第四张图像最终应该出现在右图上方的圆圈中。但当吗?最好的模型预测这将发生在2037年，但由于星团透镜的质量分布和恒星爆炸的亮度历史的模糊性，这个日期大约有两年的不确定性。通过精确的预测和警惕的监测，生活在16年后的地球人也许能够捕捉到这第四张图像——也许可以同时了解更多关于星系团和超新星的信息。探索+拓展：APOD研究生研究职位开放
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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. Discovery + Outreach: Graduate student research position open for APOD