The ancient main-sequence solar proxy HIP 102152 unveils the activity and rotational fate of our Sun

We present a detailed analysis of the possible future Sun’s rotational evolution scenario based on the 8 Gyr-old solar twin HIP 102152. Using HARPS high-cadence observations (and TESS light curves), we analyzed the modulation of a variety of activity proxies (Ca II, HI Balmer, and Na I lines), finding a strong rotational signal of 35.7 $\pm$ 1.4 days ($\log B_{\mathrm{f}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{o}\mathrm{r}}\sim 70$, in the case of Ca II K line). This value matches with the theoretical expectations regarding the smooth rotational evolution of the Sun towards the end of the main-sequence, validating the use of gyrochronology after solar age.