Sophie Stucki
IEEC / ICE-CSIC / UAB

Abstract
The radial-velocity (RV) signal induced by an Earth-like planet around a Sun-like star is only of the order of 10 cm/s. At this level of precision, variability caused by stellar magnetic activity can easily obscure planetary signals, making it essential to disentangle stellar activity from planetary signatures. Thanks to its proximity, the Sun provides a unique benchmark for testing our ability to model and mitigate solar activity at the precision required to detect Earth analogs. I will present a stringent validation of the physics-based StarSim/SunSim framework against solar observations.
SunSim uses images of the solar surface from SDO/HMI to identify magnetic features such as spots and faculae and, using first-principles spectra derived from 3D MHD simulations from MURaM, predicts the resulting total solar irradiance (TSI) and RV variability. Comparisons with HARPS-N observations show that SunSim reproduces solar activity from daily timescales up to the solar cycle, leaving a residual RV scatter (RMS) of only 79 cm/s over a decade. This performance approaches the intrinsic precision of the observations and is comparable to state-of-the-art data-driven approaches.
Finally, injection–recovery experiments show that removing stellar activity with a physics-based model improves our ability to recover planetary signals, pushing detection toward lower-mass, potentially Earth-like exoplanets. Looking ahead, observations from the PoET solar telescope will provide spatially resolved spectra of different solar surface features, offering a new opportunity to further test and refine solar MURaM models.

2026 October 14, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Classroom)
Rua das Estrelas, 4150-762 Porto