Planet mass ratios with respect to projected separation. Only planets that belong to young systems (<0.1 Gyr) are displayed, with the exception of the circumbinary planet Ross 458 c. HD 106906 b has the lowest mass ratio beyond 100 au. HIP 78530 b and HIP 77900 b are its two closest neighbors in the diagram. Being identified as brown dwarfs, they may have formed in situ by cloud collapse. Data retrieved from the exoplanets.eu database.