Planet formation models indicate that the formation of giant planets is substantially harder around low-mass stars due to the scaling of protoplanetary disc masses with stellar mass. The discovery of giant planets orbiting such low-mass stars thus imposes strong constraints on giant planet formation processes. Here we report the discovery of a transiting giant planet orbiting a 0.207 ± 0.011 M_⊙ star. The planet, TOI-6894 b, has a mass and radius of M_P = 0.168 ± 0.022 M_J (53.4 ± 7.1 M_⊕) and R_P = 0.855 ± 0.022 R_J and probably includes 12 ± 2 M_⊕ of metals. The discovery of TOI-6894 b highlights the need for a better understanding of giant planet formation mechanisms and the protoplanetary disc environments in which they occur. The extremely deep transits (17% depth) make TOI-6894 b one of the most accessible exoplanetary giants for atmospheric characterization observations, which will be key for fully interpreting the formation history of this notable system and for the study of atmospheric methane chemistry.

行星形成模型表明，由于原行星盘质量与恒星质量的缩放，在低质量恒星周围形成巨行星要困难得多。因此，发现围绕这些低质量恒星运行的巨行星对巨行星的形成过程施加了强大的限制。在这里，我们报告了一颗凌日巨行星的发现，它围绕着一颗 0.207 ± 0.011 M_⊙ 的恒星运行。这颗行星 TOI-6894 b 的质量和半径为 M_P = 0.168 ± 0.022 M_J （53.4 ± 7.1 M_⊕） 和 R_P = 0.855 ± 0.022 R_J，可能包括 12 ± 2 M _⊕ 的金属。TOI-6894 b 的发现凸显了更好地了解巨行星形成机制及其发生的原行星盘环境的必要性。极深的凌日（17% 深度）使 TOI-6894 b 成为大气特征观测最容易获得的系外行星巨行星之一，这将是全面解释这个著名系统的形成历史和研究大气甲烷化学的关键。