For the first time, scientists have made a clear X-ray detection of chlorine and potassium in the wreckage of a star using data from the Japan-led XRISM (X-ray Imaging and Spectroscopy Mission) spacecraft.
科学家们首次利用日本主导的 XRISM（X 射线成像和光谱任务）航天器的数据，对恒星残骸中的氯和钾进行了清晰的 X 射线检测。
The Resolve instrument aboard XRISM , pronounced “crism,” discovered these elements in a supernova remnant called Cassiopeia A or Cas A, for short. The expanding cloud of debris is located about 11,000 light-years away in the northern constellation Cassiopeia.
XRISM 上的 Resolve 仪器（发音为“crism”）在称为“仙后座 A”或简称“Cas A”的超新星遗迹中发现了这些元素。不断扩大的碎片云位于距仙后座约 11,000 光年远的北部星座。
“This discovery helps illustrate how the deaths of stars and life on Earth are fundamentally linked,” said Toshiki Sato, an astrophysicist at Meiji University in Tokyo. “Stars appear to shimmer quietly in the night sky, but they actively forge materials that form planets and enable life as we know it. Now, thanks to XRISM, we have a better idea of when and how stars might make crucial, yet harder-to-find, elements.”
东京明治大学的天体物理学家佐藤敏树说：“这一发现有助于说明恒星的死亡和地球上的生命之间是如何存在根本联系的。” “星星似乎在夜空中静静地闪烁，但它们积极地锻造形成行星的材料，并为我们所知的生命提供支持。现在，多亏了 XRISM，我们对恒星何时以及如何制造关键但更难找到的元素有了更好的了解。”
A paper about the result published Dec. 4 in Nature Astronomy. Sato led the study with Kai Matsunaga and Hiroyuki Uchida, both at Kyoto University in Japan. JAXA (Japan Aerospace Exploration Agency) leads XRISM in collaboration with NASA, along with contributions from ESA (European Space Agency) . NASA and JAXA also codeveloped the Resolve instrument.
有关该结果的论文于 12 月 4 日发表在《自然天文学》上。佐藤与日本京都大学的 Kai Matsunaga 和 Hiroyuki Uchida 一起领导了这项研究。 JAXA（日本宇宙航空研究开发机构）与 NASA 合作领导 XRISM，ESA（欧洲航天局）也做出了贡献。 NASA 和 JAXA 还共同开发了 Resolve 仪器。
Stars produce almost all the elements in the universe heavier than hydrogen and helium through nuclear reactions. Heat and pressure fuse lighter ones, like carbon, into progressively heavier ones, like neon, creating onion-like layers of materials in stellar interiors.
恒星通过核反应产生宇宙中几乎所有比氢和氦重的元素。热量和压力将较轻的物质（如碳）融合成逐渐较重的物质（如氖），在恒星内部形成洋葱状的材料层。
Nuclear reactions also take place during explosive events like supernovae , which occur when stars run out of fuel, collapse, and explode. Elemental abundances and locations in the wreckage can, respectively, tell scientists about the star and its explosion, even after hundreds or thousands of years.
核反应也会在超新星等爆炸事件中发生，超新星是在恒星耗尽燃料、坍塌和爆炸时发生的。即使在数百年或数千年后，残骸中的元素丰度和位置也可以分别告诉科学家关于这颗恒星及其爆炸的信息。
Some elements — like oxygen, carbon, and neon — are more common than others and are easier to detect and trace back to a particular part of the star’s life.
有些元素——比如氧、碳和氖——比其他元素更常见，也更容易检测和追溯到恒星生命的特定部分。
Other elements — like chlorine and potassium — are more elusive. Since scientists have less data about them, it’s more difficult to model where in the star they formed. These rarer elements still play important roles in life on Earth. Potassium , for example, helps the cells and muscles in our bodies function, so astronomers are interested in tracing its cosmic origins.
其他元素——如氯和钾——则更加难以捉摸。由于科学家关于它们的数据较少，因此很难对它们在恒星中形成的位置进行建模。这些稀有元素仍然在地球生命中发挥着重要作用。例如，钾有助于我们体内的细胞和肌肉发挥功能，因此天文学家有兴趣追踪其宇宙起源。
The roughly circular Cas A supernova remnant spans about 10 light-years, is over 340 years old, and has a superdense neutron star at its center — the remains of the original star’s core. Scientists using NASA’s Chandra X-ray Observatory had previously identified signatures of iron, silicon, sulfur, and other elements within Cas A.
大致呈圆形的Cas A超新星遗迹横跨约10光年，已有340多年的历史，其中心有一颗超密中子星——原始恒星核心的遗迹。科学家们利用 NASA 钱德拉 X 射线天文台此前已经确定了 Cas A 中铁、硅、硫和其他元素的特征。
In the hunt for other elements, the team used the Resolve instrument aboard XRISM to look at the remnant twice in December 2023. The researchers were able to pick out the signatures for chlorine and potassium, determining that the remnant contains ratios much higher than expected. Resolve also detected a possible indication of phosphorous, which was previously discovered in Cas A by infrared missions.
在寻找其他元素的过程中，该团队于 2023 年 12 月使用 XRISM 上的 Resolve 仪器对残留物进行了两次观察。研究人员能够找出氯和钾的特征，确定残留物的含量比预期高得多。 Resolve 还检测到了可能存在磷的迹象，这是之前通过红外任务在 Cas A 中发现的。
“Resolve’s high resolution and sensitivity make these kinds of measurements possible,” said Brian Williams, the XRISM project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Combining XRISM’s capabilities with those of other missions allows scientists to detect and measure these rare elements that are so critical to the formation of life in the universe.”
“Resolve 的高分辨率和灵敏度使此类测量成为可能，”位于马里兰州格林贝尔特的 NASA 戈达德太空飞行中心的 XRISM 项目科学家 Brian Williams 说。 “将 XRISM 的功能与其他任务的功能相结合，使科学家能够检测和测量这些对宇宙生命形成至关重要的稀有元素。”
The astronomers think stellar activity could have disrupted the layers of nuclear fusion inside the star before it exploded. That kind of upheaval might have led to persistent, large-scale churning of material inside the star that created conditions where chlorine and potassium formed in abundance.
天文学家认为，恒星活动可能在恒星爆炸之前破坏了恒星内部的核聚变层。这种剧变可能导致恒星内部物质持续大规模搅动，从而为氯和钾的大量形成创造了条件。
The scientists also mapped the Resolve observations onto an image of Cas A captured by Chandra and showed that the elements were concentrated in the southeast and northern parts of the remnant.
科学家们还将 Resolve 观测结果映射到钱德拉捕获的 Cas A 图像上，结果表明这些元素集中在遗迹的东南部和北部。
This lopsided distribution may mean that the star itself had underlying asymmetries before it exploded, which Chandra data indicated earlier this year in a study Sato led.
这种不平衡的分布可能意味着恒星本身在爆炸之前就存在潜在的不对称性，钱德拉数据在今年早些时候佐藤领导的一项研究中表明了这一点。
“Being able to make measurements with good statistical precision of these rarer elements really helps us understand the nuclear fusion that goes on in stars before and during supernovae,” said co-author Paul Plucinsky, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian in Cambridge, Massachusetts. “We suspected a key part might be asymmetry, and now we have more evidence that’s the case. But there’s still a lot we just don’t understand about how stars explode and distribute all these elements across the cosmos.”
“能够以良好的统计精度对这些稀有元素进行测量确实有助于我们了解超新星爆发之前和期间恒星中发生的核聚变，”合著者、天体物理学中心的天体物理学家保罗·普鲁辛斯基说。位于马萨诸塞州剑桥的哈佛大学和史密森尼学会。 “我们怀疑一个关键部分可能是不对称性，现在我们有更多证据表明情况确实如此。但对于恒星如何爆炸以及如何将所有这些元素分布到宇宙中，我们还有很多不明白的地方。”
By Jeanette Kazmierczak NASA’s Goddard Space Flight Center , Greenbelt, Md.
作者：Jeanette Kazmierczak 美国宇航局戈达德太空飞行中心，马里兰州格林贝尔特
Media Contact: Claire Andreoli 301-286-1940 NASA’s Goddard Space Flight Center, Greenbelt, Md.
媒体联系人：克莱尔·安德烈奥利 (Claire Andreoli) 301-286-1940 美国宇航局戈达德太空飞行中心，马里兰州格林贝尔特