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首页> 外文期刊>Nature >A candidate super-Earth planet orbiting near the snow line of Barnard's star
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A candidate super-Earth planet orbiting near the snow line of Barnard's star

机译：候选超地球行星在巴纳德恒星的雪线附近运行

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Barnard's star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs(1), it is the closest single star to the Sun; only the three stars in the alpha Centauri system are closer. Barnard's star is also among the least magnetically active red dwarfs known(2,3) and has an estimated age older than the Solar System. Its properties make it a prime target for planetary searches; various techniques with different sensitivity limits have been used previously, including radial-velocity imagine(4-6), astrometry(7,8 )and direct imaging(9), but all ultimately led to negative or null results. Here we combine numerous measurements from high-precision radial-velocity instruments, revealing the presence of a low-amplitude periodic signal with a period of 233 days. Independent photometric and spectroscopic monitoring, as well as an analysis of instrumental systematic effects, suggest that this signal is best explained as arising from a planetary companion. The candidate planet around Barnard's star is a cold super-Earth, with a minimum mass of 3.2 times that of Earth, orbiting near its snow line (the minimum distance from the star at which volatile compounds could condense). The combination of all radial-velocity datasets spanning 20 years of measurements additionally reveals a long-term modulation that could arise from a stellar magnetic-activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the candidate planet has a maximum angular separation of 220 milliarcseconds from Barnard's star, making it an excellent target for direct imaging and astrometric observations in the future.
机译：巴纳德的恒星是红矮星，并且具有所有已知恒星中最大的固有运动（在天空中出现明显的运动）。相距1.8秒差距（1），它是离太阳最近的单星；只有半人马座星系中的三颗恒星更接近。巴纳德的恒星也是已知的磁活动最弱的红矮星之一（2,3），估计年龄比太阳系还早。它的特性使其成为行星搜索的主要目标；先前已经使用了具有不同灵敏度限制的各种技术，包括径向速度想象（4-6），天文测量（7,8）和直接成像（9），但所有这些最终都导致阴性或无效结果。在这里，我们结合了高精度径向速度仪器的大量测量结果，揭示了一个低振幅周期信号的存在，周期为233天。独立的光度和光谱监测以及对仪器系统影响的分析表明，最好将这一信号解释为来自行星伴侣。巴纳德恒星周围的候选行星是一个寒冷的超级地球，其最小质量是地球质量的3.2倍，在其雪线（与恒星之间最短的距离，挥发性化合物可以凝结的最小距离）附近公转。跨越20年测量的所有径向速度数据集的组合还进一步揭示了长期调制，这可能是由于恒星的磁活动周期或更远的行星物体引起的。由于靠近太阳，候选行星与巴纳德恒星的最大角距为220毫秒，这使其成为未来直接成像和天文观测的绝佳目标。

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