中文导读

一项新研究提出，一颗白矮星周围可能形成了由恒星遗留物质构成的“第二代行星”。文章沿着化学证据、亮度信号和仍待确认的局限，解释这一判断是怎样形成的。

正文

A dead star may seem like the end of a planetary system. Yet a new study suggests that one white dwarf may have helped create a new world from material it threw into space. Researchers call the object a second-generation planet candidate. Its story is unusual because most planets, including Earth, form when their stars are young. The possibility changes how astronomers think about the life of planetary systems.

本段译文

一颗恒星死亡后，行星系统似乎也应走到尽头。然而，一项新研究表明，一颗白矮星可能用自己抛入太空的物质造出了一个新世界。研究人员称这个天体为“第二代行星候选体”。它的经历不同寻常，因为包括地球在内的大多数行星都形成于恒星年轻时。这种可能性正在改变天文学家对行星系统生命周期的认识。

The star, HS 0209+0832, is a white dwarf, the hot core left after a star runs out of fuel. Hubble first observed it in 1999. Its data contained about 100 chemical lines that scientists could not identify at the time. A research team later studied those old records again with a better chemical database.

本段译文

这颗名为 HS 0209+0832 的恒星是一颗白矮星，也就是恒星耗尽燃料后留下的炽热核心。哈勃望远镜于1999年首次观测到它。当时的数据包含约100条科学家无法识别的化学谱线。后来，一个研究团队借助更完善的化学数据库重新分析了这些旧记录。

The new analysis found large amounts of zinc, copper and niobium in the star’s atmosphere. Niobium was especially important. Dying stars can make this heavy element during a late stage of their lives. The researchers found little iron or silicon, although these materials are common in rocky planets. This strange pattern did not look like ordinary space rock falling onto the white dwarf.

本段译文

新的分析在这颗恒星的大气层中发现了大量锌、铜和铌。铌尤其重要。垂死的恒星能在生命晚期生成这种重元素。研究人员只发现了少量铁和硅，尽管这些物质在岩石行星中很常见。这种奇特组合不像是普通太空岩石落到白矮星上所留下的。

The team offers another explanation. When the original star died, it sent material away. Some of that material may have formed a disk and then a new gas giant. A companion star may have helped pull the material into orbit. The nearby white dwarf is still very hot, so its radiation may be removing gas from the planet. That gas then falls back onto the star and leaves a chemical signal that telescopes can detect.

本段译文

研究团队提出了另一种解释。原来的恒星死亡时向外抛出了物质，其中一部分可能先形成圆盘，随后形成新的气态巨行星。一颗伴星可能帮助这些物质进入轨道。附近的白矮星仍然很热，因此它的辐射可能正在剥离行星上的气体。这些气体随后落回恒星，并留下望远镜能够探测到的化学信号。

Data from NASA’s TESS satellite added a second kind of evidence. It showed a small change in brightness every 4.4 days. The period fits a Jupiter-sized object moving very close to the white dwarf, at a distance of about 6 million kilometers. However, the signal could also come from a long tail of gas crossing in front of the star.

本段译文

NASA 的 TESS 卫星提供了另一类证据。它每隔4.4天就观测到一次微小的亮度变化。这个周期符合一个木星大小的天体在距离白矮星约600万公里处近距离运行的情况。不过，这一信号也可能来自一条从恒星前方经过的长气体尾。

This is why the word “candidate” matters. The chemical evidence and the regular signal support the same idea, but they do not yet provide a direct picture of the planet. The scientists hope to use more observations to test the explanation. If it is confirmed, the finding will show that planet formation does not always end when a star dies. Old material can sometimes become the beginning of something new. It may also help teams search for similar worlds around other white dwarfs.

本段译文

这正是“候选体”一词很重要的原因。化学证据和规律信号支持同一种解释，但它们尚未提供行星的直接图像。科学家希望通过更多观测来检验这一解释。如果得到确认，这项发现将表明，行星形成并不总在恒星死亡时终止。旧物质有时可以成为新事物的开端。它也可能帮助团队寻找其他白矮星周围的类似世界。

新闻来源

• Reuters — Alien ‘phoenix planet’ was born from the ashes of a dying star
• DW — Hallan el primer “planeta fénix” tras la muerte de su sol
• NASA — Suspected Second-generation Planet Solves NASA Hubble Cold Case
• Nature Astronomy — Discovery of a second-generation planet candidate accreting onto a white dwarf

✳更多文章 →