Abstract

To understand exoplanetary systems, we can study their mass-radius relationship or lack thereof. The HARPS -N Collaboration has been leading the efforts to fill and interpret the mass-radius diagram of small planets by combining space photometry, Gaia astrometry and radial velocities. Determining a precise as-well-as accurate planet mass can only be determined with well-sampled, stable, and precise observations combined with advanced computational efforts and new extraction and processing techniques. The biggest challenge remains the stellar activity processes, mimicking and hiding planetary signals. With the HARPS -N Collaboration, we have been studying the Sun-as-a-star for 6 years, providing a dataset where we truly have no planetary signals and can study stellar behaviour in more detail. In this talk, I will give an overview on the leading efforts of our collaboration to fill the mass-radius diagram, an insight in new LSD -based processing techniques, and the behaviour over time of the standard activity indicators using Solar data.