Observed planet mass vs. stellar mass. The blue dots are the planets only detected by radial velocity surveys with a low mass limit, and the red dots are the planets with true masses either from a combined radial velocity and transit surveys, or from transit timing variation measurements. The selected planets also have relatively precise stellar mass measurements (Δϵ = ΔM_⋆∕M_⋆ ≤ 20%). The black line is adopted from Eq. (39), indicating the pebble isolation mass (see details in Sect. 5), and the gray lines show a factor of two variation. The masses of planets seem to correlate with the masses of their central stars. The names of typically planetary systems around very low-mass stars are labeled in green, including TRAPPIST-1, (Gillon et al. 2016), Proxima Centauri (Anglada-Escudé et al. 2016), Ross 128 (Bonfils et al. 2018), LHS 1140 (Dittmann et al. 2017), YZ Cet (Astudillo-Defru et al. 2017), Teegarden’s star (Zechmeister et al. 2019), GJ 1214 (Charbonneau et al. 2009), GJ 1265 (Luque et al. 2018), GJ 1132 (Berta-Thompson et al. 2015), GJ 1061 (Dreizler et al. 2019), and GJ 357 (Luque et al. 2019).