We summarize the cutting-edge states of the exoplanet and disk observations and present a comprehensive panoptic view of modern core accretion planet formation scenarios, including dust growth and radial drift, planetesimal formation by the streaming instability, core growth by planetesimal accretion and pebble accretion. 

Pebble-driven planet formation around very low-mass stars and brown dwarfs

Liu, Lambrechts, Johansen, Ilaria & Henning 2020, A&A [ADS] [arxiv]

We conduct a planet population synthesis study to investigate the formation of planets around very low-mass stars and brown dwarfs in the (sub)stellar mass range between 0.01 M⊙ and 0.1 M⊙. We start with protoplanets formed by the streaming instability and trace their subsequent growth and migration. We find the final masses of planets scales linearly with their central hosts, maximumly reaching the pebble isolation mass. The giant planets cannot form in such low-mass (sub)stellar host systems. 


Super-Earth masses sculpted by pebble isolation around stars of different masses

Liu, Lambrechts, Johansen, Liu 2019, A&A [ADS] [arxiv]

We study the formation and evolution of protoplanets around stars in the stellar mass range of 0.08 M⊙-1 M⊙. By Monte Carlo sampling of the initial conditions, the growth and migration of a large number of individual protoplanets were simulated in a population synthesis manner. The forming planets are compared with the observed exoplanets in terms of mass, semimajor axis, metallicity, and water content.

Our model shows that the characteristic mass of super-Earth is set by the pebble isolation mass. Super-Earth masses increase linearly with the mass of its stellar host, which corresponds to one Earth mass around a late M-dwarf star and 20 Earth masses around a solar-mass star. In addition, the low-mass planets, up to 20 M⊕, can form around stars with a wide range of metallicities, while massive gas giant planets are preferred to grow around metal-rich stars. Our model succeeds in quantitatively reproducing several important observed properties of exoplanets and correlations with their stellar hosts.