Giant planet formation at the pressure maxima of protoplanetary disks

Abstract

Context. Recent high-resolution observations of protoplanetary disks have revealed ring-like structures that can be associated to pressure maxima. Pressure maxima are known to be dust collectors and planet migration traps. The great majority of planet formation studies are based either on the pebble accretion model or on the planetesimal accretion model. However, recent studies proposed hybrid accretion of pebbles and planetesimals as a possible formation mechanism for Jupiter. Aims. We aim to study the full process of planet formation consisting of dust evolution, planetesimal formation, and planet growth at a pressure maximum in a protoplanetary disk. Methods. We compute, through numerical simulations, the gas and dust evolution in a protoplanetary disk, including dust growth, fragmentation, radial drift, and particle accumulation at a pressure maximum. The pressure maximum appears due to an assumed viscosity transition at the water ice line. We also consider the formation of planetesimals by streaming instability and the formation of a moon-size embryo that grows into a giant planet by the hybrid accretion of pebbles and planetesimals, all within the pressure maximum. Results. We find that the pressure maximum is an efficient collector of dust drifting inwards. The condition of planetesimal formation by streaming instability is fulfilled due to the large amount of dust accumulated at the pressure bump. Subsequently, a massive core is quickly formed (in ~104 yr) by the accretion of pebbles. After the pebble isolation mass is reached, the growth of the core slowly continues by the accretion of planetesimals. The energy released by planetesimal accretion delays the onset of runaway gas accretion, allowing a gas giant to form after ~1 Myr of disk evolution. The pressure maximum also acts as a migration trap. Conclusions. Pressure maxima generated by a viscosity transition at the water ice line are preferential locations for dust traps, planetesimal formation by streaming instability, and planet migration traps. All these conditions allow the fast formation of a giant planet by the hybrid accretion of pebbles and planetesimals.

How drifting and evaporating pebbles shape giant planets

“…This approach to the dust evolution is within a few percent compared to a "full" model, which includes individual velocities for all grains within the grain size distribution (Birnstiel et al 2012). Previous planetesimal (Dr ążkowska et al 2016;Dr ążkowska & Alibert 2017) and planet formation simulations (Guilera et al 2020) have used this full model. While the full model allows for a slightly larger accuracy for the dust evolution, the here used approach of Birnstiel et al (2012) results in a shorter computational run time, needed to probe all the different disk and planetary parameters (Table 3) in our work.…”

“…2.1) and depend on the initial solid to gas ratio ( 0 ). This approach is an improvement compared to previous planet formation simulations via pebble accretion, where mostly a simplified pebble growth and drift model is used (e.g., Bitsch et al 2015;Ndugu et al 2018), but approaches using a model with accretion rates depending on a full pebble size distribution have also been implemented in other works (Guilera et al 2020;Dr ążkowska et al 2021).…”

How drifting and evaporating pebbles shape giant planets

“…Planetary atmospheres can also be enriched via collisions (Ogihara et al 2021) or via the accretion of planetesimals. This can happen either during the buildup of the planetary atmosphere itself (Pollack et al 1996), which might even delay runaway gas accretion (Alibert et al 2018;Venturini & Helled 2020;Guilera et al 2020), or when a large gaseous envelope has already formed (Shibata & Ikoma 2019;Shibata et al 2020). The accretion efficiency depends crucially on the size of the planetesimals (Levison et al 2010;Fortier et al 2013; and the migration speed of the planet (Tanaka & Ida 1999).…”

How dust fragmentation may be beneficial to planetary growth by pebble accretion

“…In terms of pebble flux, substructures cause the pileup of pebbles, likely speeding up local growth of planets located inside the pressure bump (Guilera et al 2020;Morbidelli 2020). The existence of a long-lasting substructure may be a way to enable the growth of giant planets at large orbital distances.…”

“…Nevertheless, most of the works concerned with planetary growth via pebble accretion published to date neglect the effect that the fragmentation of pebbles has on their sizes and flux (the exceptions are Chambers 2016, Guilera et al 2020, and Venturini et al 2020a. In this paper, for the first time, we study the growth of a planetary embryo by pebble accretion in connection with a self-consistent dust evolution model, considering the full size distribution obtained in a detailed dust coagulation simulation.…”