Forty million years ago, a star in a nearby galaxy exploded, spewing material across space and generating a brilliant beacon of light. That light traveled across the cosmos, reaching Earth June 29, 2025, where it was detected by the All-Sky Automated Survey for Supernovae. Astronomers immediately turned their resources to this new supernova, designated 2025pht, to learn more about it. But one team of scientists instead turned to archives, seeking to use pre-supernova images to identify exactly which star among many had exploded. And they succeeded.
四千万年前，附近星系中的一颗恒星爆炸了，将物质喷射到太空中并产生了明亮的灯塔。这道光穿过宇宙，于 2025 年 6 月 29 日到达地球，并被全天超新星自动巡天探测到。天文学家立即将资源转向这颗名为 2025pht 的新超新星，以了解更多信息。但一组科学家转而求助于档案，试图利用超新星爆发前的图像来准确识别众多恒星中哪一颗发生了爆炸。他们成功了。
“We’ve been waiting for this to happen – for a supernova to explode in a galaxy that Webb had already observed. We combined Hubble and Webb data sets to completely characterize this star for the first time,” said lead author Charlie Kilpatrick of Northwestern University.
“我们一直在等待这种情况的发生——等待一颗超新星在韦伯已经观测到的星系中爆炸。我们结合哈勃和韦伯的数据集，首次完整地描述了这颗恒星的特征，”西北大学的主要作者查理·基尔帕特里克说。
By carefully aligning Hubble and Webb images taken of NGC 1637, the team was able to identify the progenitor star in images taken by Webb’s MIRI (Mid-Infrared Instrument) and NIRCam (Near-Infrared Camera) in 2024. They found that the star appeared surprisingly red – an indication that it was surrounded by dust that blocked shorter, bluer wavelengths of light.
通过仔细对齐哈勃和韦伯在 NGC 1637 上拍摄的图像，研究小组能够在韦伯的 MIRI（中红外仪器）和 NIRCam（近红外相机）于 2024 年拍摄的图像中识别出这颗祖星。他们发现这颗恒星呈现出令人惊讶的红色，这表明它被尘埃包围，阻挡了更短、更蓝波长的光。
“It’s the reddest, most dusty red supergiant that we’ve seen explode as a supernova,” said graduate student and co-author Aswin Suresh of Northwestern University.
西北大学的研究生兼合著者阿斯温·苏雷什（Aswin Suresh）说：“这是我们所见过的最红、尘埃最多的红超巨星，它是超新星爆炸。”
This excess of dust could help explain a long-standing problem in astronomy that could be described as the case of the missing red supergiants. Astronomers expect the most massive stars that explode as supernovas to also be the brightest and most luminous. So, they should be easy to identify in pre-supernova images. However, that hasn’t been the case.
这种过量的尘埃可能有助于解释天文学中一个长期存在的问题，即红超巨星失踪的情况。天文学家预计，作为超新星爆炸的质量最大的恒星也将是最亮、最明亮的。因此，它们应该很容易在超新星爆发前的图像中识别出来。然而，事实并非如此。
One potential explanation is that the most massive aging stars are also the dustiest. If they’re surrounded by large quantities of dust, their light could be dimmed to the point of undetectability. The Webb observations of supernova 2025pht support that hypothesis.
一种可能的解释是，质量最大的老化恒星也是尘埃最多的。如果它们被大量灰尘包围，它们的光线可能会变暗到无法检测到的程度。韦伯对超新星 2025pht 的观测支持了这一假设。
“I’ve been arguing in favor of that interpretation, but even I didn’t expect to see it as extreme as it was for supernova 2025pht. It would explain why these more massive supergiants are missing because they tend to be more dusty,” said Kilpatrick.
“我一直赞成这种解释，但即使是我也没想到它会像 2025 年超新星爆发那样极端。这可以解释为什么这些质量更大的超巨星失踪了，因为它们往往含有更多尘埃，”基尔帕特里克说。
The team was not only surprised by the amount of dust, but also by its composition. Applying computer models to the Webb observations indicated that the dust is likely carbon-rich, when astronomers would have expected it to be more silicate-rich. The team speculates that this carbon might have been dredged up from the star’s interior shortly before it exploded.
研究小组不仅对灰尘的数量感到惊讶，而且对其成分也感到惊讶。将计算机模型应用于韦伯观测表明，这些尘埃可能富含碳，而天文学家原本预计它更富含硅酸盐。研究小组推测，这些碳可能是在恒星爆炸前不久从恒星内部挖出来的。
“Having observations in the mid-infrared was key to constraining what kind of dust we were seeing,” said Suresh.
苏雷什说：“在中红外波段进行观测是限制我们所看到的尘埃类型的关键。”
The team now is working to look for similar red supergiants that may explode as supernovas in the future. Observations by NASA’s upcoming Nancy Grace Roman Space Telescope may help this search. Roman will have the resolution, sensitivity, and infrared wavelength coverage to not only see these stars, but also potentially witness their variability as they “burp” out large quantities of dust near the end of their lives.
该团队目前正在努力寻找未来可能爆炸为超新星的类似红超巨星。美国宇航局即将推出的南希·格雷斯·罗马太空望远镜的观测可能有助于这项研究。罗曼将拥有分辨率、灵敏度和红外波长覆盖范围，不仅可以看到这些恒星，而且还可能见证它们在生命即将结束时“打嗝”出大量尘埃时的变化。
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
詹姆斯·韦伯太空望远镜是世界上首屈一指的太空科学天文台。韦伯正在解开太阳系中的谜团，展望其他恒星周围的遥远世界，并探索宇宙的神秘结构和起源以及我们在其中的位置。韦伯是由 NASA 及其合作伙伴 ESA（欧洲航天局）和 CSA（加拿大航天局）领导的一项国际计划。
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