The dynamical evolution of the asteroid belt in the pebble accretion scenario

Transcription

1 The dynamical evolution of the asteroid belt in the pebble accretion scenario S. Pirani 1, A. Johansen 1, B. Bitsch 1, A. J. Mustill 1 and D. Turrini 2,3 1 Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Lund, Sweden. 2 Institute for Space Astrophysics and Planetology INAF-IAPS, Via Fosso del Cavaliere 100, Rome, Italy. 3 Departamento de Fisica, Universidad de Atacama, Copayapu 485, Copiapo, Chile. 15 May 2017 Impacts in Planetary Systems

2 Formation of the giant planets Gravitational instability model Core accretion model Large planets in wide orbits Planetesimal accretion Pebble accretion 15 May 2017 Impacts in Planetary Systems 1

3 Pebble accretion Observations of mm- cm-sized particles in protoplanetary discs; Pebbles are accreted from the entire Hill sphere; Rapid growth for the cores of the giant planets 15 May 2017 Impacts in Planetary Systems 2

4 Migration of the Giant Planets Type I migration Internal density wake exerts a positive torque; External density wake exerts a negative torque; Type II migration The external torque dominates, causing the planet to lose angular momentum, and hence to migrate inward. The planet opens a gap in the disc; External torque forces the planet to migrate inward; Slower migration rate than the Type I because the planet must wait until the gap is refilled behind it. Images from: 15 May 2017 Impacts in Planetary Systems 3

5 Growth tracks Jupiter Saturn Uranus Neptune M P /M E 10 1 runaway accretion of gas The planet reach the pebble isolation mass Ice giants never reach the pebble isolation mass semimajor axis 15 May 2017 Impacts in Planetary Systems 4

6 Which are the implications of this new scenario on our Solar System? The aim of our work is to test the large-scale migration of the giant planets predicted in pebble accretion scenario and analyze its influence on the asteroid belt and on the other small-body populations of our solar system. 15 May 2017 Impacts in Planetary Systems 5

7 Methods Mercury N-body code (Chambers, 1999); Growth tracks of Gas Giants with cores grown by pebble accretion (Bitsch et al., 2015); Size distribution of asteroid and planetary embryos grown by accretion of chondrules onto planetesimal seeds formed by the streaming instability (Johansen et al., 2015). Gas drag effects for the embryos (Cresswell et al., 2007). 15 May 2017 Impacts in Planetary Systems 6

8 Effects on the asteroid belt eccentricity Time = 0 Myr 126 embryos from Ceres to Mars size; 8000 small particles. Disc lifetime: 3 Myr semimajor axis 15 May 2017 Impacts in Planetary Systems 7

9 Migration Scenario 1 Time = 150 Myr (migration scenario) 0.8 eccentricity semimajor axis 15 May 2017 Impacts in Planetary Systems 8

10 Migration Scenario 1 Time = 150 Myr (migration scenario) [bodies from 4 to 5 au] 0.8 eccentricity semimajor axis 15 May 2017 Impacts in Planetary Systems 9

11 What happens to the bodies within the giant planet s path? We added Uranus and Neptune growth tracks; small particles from 5 to 25.5 au; Aerodynamic gas drag effects. 15 May 2017 Impacts in Planetary Systems 10

12 Outer solar system simulations 15 May 2017 Impacts in Planetary Systems 11

13 Outer solar system simulations 1 Time = 100 Myr 0.8 eccentricity semimajor axis 15 May 2017 Impacts in Planetary Systems 12

14 Outer solar system simulations Time = 100 Myr from 5-8 au from 8-11 au from au from au from au from au from au Particles from the outer solar system end up in the asteroid belt; eccentricity :2 resonance - Hilda s family Hilda s family is captured from a region about 7-8 au and carried until 4 au; :1 resonance - Jupiter s Trojans Jupiter s Trojans come from a region at 18 au semimajor axis 15 May 2017 Impacts in Planetary Systems 13

15 Summary We simulated the large-scale migration predicted for the giant planets in the pebble accretion scenario; The migration of the giant planets injects material inside the asteroid belt; The Hilda s family is trapped during the migration in a region different from thecurrent location; Trojans are captured from the birth region of the giant planets. 15 May 2017 Impacts in Planetary Systems 14

16 Thank you! 15 May 2017 Impacts in Planetary Systems