These 45 exoplanets may be the best places to search for alien life

这45颗系外行星可能是寻找外星生命的最佳地点

Astronomers have narrowed the search for extraterrestrial life from thousands of distant worlds down to just a few dozen promising candidate planets, offering a clearer roadmap for one of science's biggest questions: Are we alone?

天文学家已经将对外星生命的搜索范围从数千个遥远的世界缩小到只有几十个有前景的候选行星，为科学上最大的问题之一提供了更清晰的路线图：我们是孤独的吗？

In a new study, a team of researchers led by Lisa Kaltenegger of the Carl Sagan Institute at Cornell University identified 45 rocky exoplanets that sit within their stars' habitable zones, where temperatures could allow liquid water to exist on their surfaces. Out of more than 6,000 known exoplanets, these worlds represent some of the most compelling places to search for alien life.

在一项新的研究中，由康奈尔大学卡尔·萨根研究所的莉莎·卡尔滕格格领导的研究团队确定了45颗位于其恒星可居住区的类岩石系外行星，这些区域的温度可能允许液态水存在于其表面。在已知的超过6,000颗系外行星中，这些世界代表了一些最有吸引力的寻找外星生命的地点。

The team used data from the European Space Agency's now-retired Gaia mission and the NASA Exoplanet Archive to refine estimates of how much stellar energy each planet receives — one of the key factors determining whether a world might be too hot, too cold or just right for life as we know it.

该团队使用了欧洲航天局现已退役的盖亚任务和美国宇航局外星行星档案的数据，以优化每颗行星接受的恒星能量的估计——这是决定一个世界是否过热、过冷或正好适合我们所知生命的关键因素之一。

But rather than simply asking which planets might host life, the team set out to answer a deeper question: What are the limits of habitability? To do that, they deliberately included worlds that push the boundaries in their catalog.

但团队并不仅仅是询问哪些行星可能存在生命，而是着手回答一个更深层次的问题：宜居的界限是什么？为此，他们在其目录中故意包含了那些挑战界限的世界。

"We know Earth is habitable, while Venus and Mars are not. We can use our solar system as a reference to search for exoplanets that receive stellar energy between what Venus and Mars get," study co-author Abigail Bohl said in a statement.

“我们知道地球适宜生存，而金星和火星则不适宜。我们可以以我们的太阳系为参考，寻找接收恒星能量介于金星和火星之间的系外行星，”研究联合作者阿比盖尔·博尔在一份声明中表示。

"Observing these planets can help us understand when habitability is lost, how much energy is too much and which planets remain habitable — or maybe never were," Bohl added.

Bohl补充道：“观察这些行星可以帮助我们理解可居住性何时丧失、多少能量过多以及哪些行星仍然适合居住——或者可能从未适合过。”

The team also considered planets with elliptical orbits; further research here might determine how much such "orbital eccentricity" a planet can have before it loses its habitability.

团队还考虑了椭圆轨道的行星；在这方面的进一步研究可能会确定一颗行星在失去可居住性之前可以有多少这样的“轨道偏心率”。

Crucially, this new exoplanet catalog is not meant to be an exhaustive list of potentially habitable worlds. Instead, it serves as a strategy for future research. The team highlighted which planets are best suited for different observation techniques, helping guide powerful instruments like the James Webb Space Telescope and other observatories to probe for biosignatures, or potential signs of life.

至关重要的是，这个新的系外行星目录并不旨在成为潜在宜居世界的详尽清单。相反，它作为未来研究的策略。团队强调了哪些行星最适合不同的观测技术，帮助指导詹姆斯·韦伯太空望远镜和其他天文台这样的强大仪器去探测生物特征或潜在的生命迹象。

"While it's hard to say what makes something more likely to have life, identifying where to look is the first key step — so the goal of our project was to say, 'Here are the best targets for observation'," said co-author Gillis Lowry, who is now a graduate student at San Francisco State University.

“虽然很难说什么因素使某物更可能存在生命，但确定寻找位置是第一关键步骤——因此我们项目的目标是指出，‘这里是观测的最佳目标，’”合著者吉利斯·洛瑞说，他现在是旧金山州立大学的研究生。

Among the most compelling targets is the TRAPPIST-1 system, about 40 light-years away, which hosts multiple potentially habitable Earth-size rocky planets. Interestingly, these worlds may be tidally locked to their star, with permanent day and night sides. Still, Trappist-1 e is considered one of the leading candidates to host liquid water.

最引人注目的目标之一是距离地球约40光年的TRAPPIST-1系统，该系统拥有多个潜在可居住的地球大小岩石行星。有趣的是，这些世界可能与它们的恒星潮汐锁定，拥有永久的昼夜面。不过，TRAPPIST-1e仍被认为是最有可能存在液态水的候选行星之一。

Another standout is LHS 1140 b, a denser, larger world considered a "super-Earth" about 48 light-years away. With a mass more than five times that of Earth and slightly higher overall density, it could be a water-rich ocean world.

另一个引人注目的是 LHS 1140 b，这是一颗更密集、更大的世界，被认为是一颗“超地球”，距离约 48 光年。其质量是地球的五倍多，总体密度略高，可能是一颗富含水的海洋世界。

Closer to home, Proxima Centauri b, orbiting our nearest stellar neighbor just 4.25 light-years away, remains tantalizing to astronomers, despite concerns about intense stellar flares that could strip away its atmosphere.

更近一些的地方，距离我们最近的恒星邻居仅4.25光年远的比邻星b，尽管存在强烈恒星耀斑可能剥离其大气层的担忧，仍然让天文学家感到非常吸引。

With next-generation observatories coming online, future observations of these 45 worlds may bring scientists closer than ever to determining whether life exists beyond Earth.

随着下一代天文台投入使用，对这45个世界的未来观测可能让科学家比以往任何时候都更接近确定地球以外是否存在生命。

A study on the research was published in the Monthly Notices of the Royal Astronomical Society on March 19.

一项关于该研究的研究成果于3月19日发表在《皇家天文学会月刊》上。