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

Abstract

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 analysed the modulation of a variety of activity proxies (Ca II, H I Balmer, and Na I lines), finding a strong rotational signal of 35.7 ± 1.4 d (log B_factor ∼ 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.