We report on the discovery of a transiting Earth-sized (0.95$R_\oplus$) planet around an M3.5 dwarf star at 57$\,$pc, K2-315b. The planet has a period of $\sim$3.14 days, i.e. ${\sim}\pi$, with an instellation of 7.45$\,$S$_{\oplus}$. The detection was made using publicly available data from $\textit{K2}$'s Campaign 15. We observed three additional transits with SPECULOOS Southern and Northern Observatories, and a stellar spectrum from Keck/HIRES, which allowed us to validate the planetary nature of the signal. The confirmed planet is well suited for comparative terrestrial exoplanetology. While exoplanets transiting ultracool dwarfs present the best opportunity for atmospheric studies of terrestrial exoplanets with the $\textit{James Webb Space Telescope}$, those orbiting mid-M dwarfs within 100$\,$pc such as K2-315b will become increasingly accessible with the next generation of observatories.

中文翻译：

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π 地球：来自 K2 厨房的 3.14 天地球大小的行星，由 SPECULOOS 团队提供温暖服务

我们报告了在 57$\,$pc, K2-315b 的 M3.5 矮星周围发现了一颗地球大小 (0.95$R_\oplus$) 的行星。这颗行星的周期为$\sim$3.14 天，即${\sim}\pi$，星座为7.45$\,$S$_{\oplus}$。检测是使用 $\textit{K2}$ 的活动 15 中的公开数据进行的。我们通过 SPECULOOS 南天文台和北天文台观察到了三个额外的凌日，以及来自 Keck/HIRES 的恒星光谱，这使我们能够验证行星的性质的信号。确认的行星非常适合比较类地系外行星学。虽然系外行星通过超冷矮星为使用 $\textit{James Webb Space Telescope}$ 对类地系外行星进行大气研究提供了最佳机会，但那些在 100$\ 范​​围内绕中 M 矮星运行的系外行星，