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COAGULATION CALCULATIONS OF ICY PLANET FORMATION AROUND 0.1-0.5 M ☉ STARS: SUPER-EARTHS FROM LARGE PLANETESTIMALS

2013; IOP Publishing; Volume: 780; Issue: 1 Linguagem: Inglês

10.1088/0004-637x/780/1/4

1538-4357

Scott J. Kenyon, Benjamin C. Bromley,

Stellar, planetary, and galactic studies

We investigate formation mechanisms for icy super-Earth mass planets orbiting at 2-20 AU around 0.1-0.5 solar mass stars. A large ensemble of coagulation calculations demonstrates a new formation channel: disks composed of large planetesimals with radii of 30-300 km form super-Earths on time scales of roughly 1 Gyr. In other gas-poor disks, a collisional cascade grinds planetesimals to dust before the largest planets reach super-Earth masses. Once icy Earth-mass planets form, they migrate through the leftover swarm of planetesimals at rates of 0.01-1 AU per Myr. On time scales of 10 Myr to 1 Gyr, many of these planets migrate through the disk of leftover planetesimals from semimajor axes of 5-10 AU to 1-2 AU. A few per cent of super-Earths might migrate to semimajor axes of 0.1-0.2 AU. When the disk has an initial mass comparable with the minimum mass solar nebula scaled to the mass of the central star, the predicted frequency of super-Earths matches the observed frequency.