近日，智利迭戈·波塔莱斯大学Kevin Hoy团队报道了在一颗恒星的亚恒星伴星周围探测到一颗行星质量级的系外伴星卫星。该研究于2026年7月22日发表在《自然》杂志上。

褐矮星占据行星与恒星之间的质量区间。在同时包含恒星和亚恒星伴星（无论是褐矮星还是系外行星）的系统中，绕该伴星运行的第三个天体可称为系外伴星卫星。系外行星的卫星可以很自然地称为系外卫星，但褐矮星伴星的卫星是否也可同样称呼尚不明确，因为该术语缺乏正式定义。尽管已发现超过6000颗系外行星，但至今尚未有任何一颗系外卫星被确凿探测到。虽然存在一些候选体，但它们未确认且仍存争议。

研究组展示了绕直接成像的褐矮星伴星CD-35 2722 B运行的系外伴星卫星的证据。他们将径向速度分析法——即用于发现首颗围绕类太阳恒星运行的系外行星的技术——应用于该褐矮星的VLT/CRIRES+光谱数据，发现了似乎来自至少一颗绕行卫星的周期性信号。据研究组所知，这是该技术首次产生褐矮星伴星周围存在卫星的证据。该最佳拟合模型包含一颗最小质量约为0.9倍木星质量、轨道周期约为170天的卫星。尽管尚不确定这颗系外伴星卫星是否符合目前尚未定义的“系外卫星”标准，但这是迈向首次无争议探测的重要一步，因为随着技术进步，同样的方法将可应用于质量更小的目标天体。

附：英文原文

Title: Planetary-mass exosatellite detected around the substellar companion of a star

Author: Hoy, Kevin, Zurlo, Alice, Pea R, Pablo A, Khler, Jana, Desidera, Silvano, Gratton, Raffaele, Lazzoni, Cecilia, Petrus, Simon, Rodler, Florian, Smoker, Jonathan, DOrazi, Valentina, Carleo, Ilaria, Giovannini, Ilaria

Issue&Volume: 2026-07-22

Abstract: Brown dwarfs occupy the mass regime between planets and stars. In systems containing both a star and a substellar companion (be it a brown dwarf or an exoplanet), a third object orbiting the companion can be called an exosatellite. Exoplanet satellites can be easily described as exomoons, but it is not clear if satellites of brown dwarf companions can be called the same, as the term lacks a formal definition. Despite more than 6,000 exoplanets being discovered1, no exomoon has ever been confidently detected. Although there are candidates, they lack confirmation and remain controversial2,3,4,5. In this work, we present evidence of an exosatellite orbiting the directly imaged brown dwarf companion CD-35 2722 B. Applying radial velocity analysis, the same technique used to discover the first exoplanet around a Solar-type star6, to VLT/CRIRES+ spectra of this brown dwarf, we find what appears to be the periodic signal of at least one orbiting satellite. This is the first time, to our knowledge, this technique has produced evidence of satellites around a companion brown dwarf. Our best-fitting model includes a satellite with a minimum mass of about 0.9 Jupiter masses and a period of around 170days. Although it is uncertain whether this exosatellite will fulfil the presently undefined criteria for qualifying as an exomoon, it is a marked step towards that first uncontroversial detection, as advancing technology will allow the same method to be applied to less massive targets.

DOI: 10.1038/s41586-026-10751-w

Source: https://www.nature.com/articles/s41586-026-10751-w