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Initial mass function of planetesimals formed by the streaming instability
Urs Schäfer, Chao-Chin Yang, Anders Johansen
The streaming instability is a mechanism to concentrate solid particles into overdense filaments that undergo gravitational collapse and form planetesimals. However, it remains unc…
Concentrating small particles in protoplanetary disks through the streaming instability
Chao-Chin Yang, Anders Johansen, Daniel Carrera
Laboratory experiments indicate that direct growth of silicate grains via mutual collisions can only produce particles up to roughly millimeters in size. On the other hand, recent…
Atmospheric Signatures of Giant Exoplanet Formation by Pebble Accretion
Nikku Madhusudhan, Bertram Bitsch, Anders Johansen +1
Atmospheric chemical abundances of giant planets lead to important constraints on planetary formation and migration. Studies have shown that giant planets that migrate through the…
The role of pebble fragmentation in planetesimal formation II. Numerical simulations
Karl Wahlberg Jansson, Anders Johansen, Mohtashim Bukhari Syed +1
Some scenarios for planetesimal formation go through a phase of collapse of gravitationally bound clouds of mm-cm-sized pebbles. Such clouds can form for example through the stream…
The role of pebble fragmentation in planetesimal formation I. Experimental study
M. Bukhari Syed, J. Blum, K. Wahlberg Jansson +1
Previous work on protoplanetary dust growth shows halt at centimeter sizes owing to the occurrence of bouncing at velocities of 0.1 and fragmentation at velocities…
The effects of external planets on inner systems: multiplicities, inclinations, and pathways to eccentric warm Jupiters
Alexander J Mustill, Melvyn B Davies, Anders Johansen
We study how close-in systems such as those detected by Kepler are affected by the dynamics of bodies in the outer system. We consider two scenarios: outer systems of giant planets…
Forming chondrules in impact splashes - II Volatile retention
Cornelis Petrus Dullemond, Daniel Harsono, Sebastian Markus Stammler +1
Solving the mystery of the origin of chondrules is one of the most elusive goals in the field of meteoritics. Recently the idea of planet(esimal) collisions releasing splashes of l…
Long-term stability of the HR 8799 planetary system without resonant lock
Ylva Gotberg, Melvyn B. Davies, Alexander Mustill +2
HR 8799 is a star accompanied by four massive planets on wide orbits. The observed planetary configuration has been shown to be unstable on a timescale much shorter than the estima…
Survival of habitable planets in unstable planetary systems
Daniel Carrera, Melvyn B. Davies, Anders Johansen
Many observed giant planets lie on eccentric orbits. Such orbits could be the result of strong scatterings with other giant planets. The same dynamical instability that produces th…
How to form asteroids from mm-sized grains
Daniel Carrera, Anders Johansen, Melvyn B. Davies
The size distribution of asteroids in the solar system suggests that they formed top-down, with 100-1000 km bodies forming from the gravitational collapse of dense clumps of small…
Spontaneous concentrations of solids through two-way drag forces between gas and sedimenting particles
Michiel Lambrechts, Anders Johansen, Holly L. Capelo +2
The behaviour of sedimenting particles depends on the dust-to-gas ratio of the fluid. Linear stability analysis shows that solids settling in the Epstein drag regime would remain h…
Hot Jupiters and Super-Earths
Alexander James Mustill, Melvyn B Davies, Anders Johansen
We explore the role of dynamics in shaping planetary system multiplicities, focussing on two particular problems. (1) We propose that the lack of close-in super-Earths in hot Jupit…
Influence of the water content in protoplanetary discs on planet migration and formation
Bertram Bitsch, Anders Johansen
The temperature and density profiles of protoplanetary discs depend crucially on the mass fraction of micrometre-sized dust grains and on their chemical composition. A larger abund…