Dynamical Friction and Planet Formation

1
Dynamical Friction and Planet Formation

• Hilke Schlichting
• Advisor Reem Sari

2
Planet Formation

• 3 Main Stages
• 1) accumulation of dust to planetesimals
• 2)runaway and oligarchic growth
• 3)late stage scattering, collisions and
  accretion among the protoplanets

3
Velocity evolution
S mass density protoplanets s mass
density planetesimals R radius protoplanet v
velocity protoplanet vH Hill velocity ?
material density O angular velocity a Hill
radius
Viscous Stirring
Dynamical Friction
v vH S/s

• Phase ends when

S s
4
Viscous Stirring
Dynamical Friction
Bdf /AstS/s
Dictates how efficiently planetesimals can be
accreted before system scatters
5
Dynamical Friction
6
Dynamical Friction in a Plane

• 2-body Problem
• Conservation of Energy Momentum
• Integration over b
• Fdf2pSGM

7
Hill coordinates
8
Hill Equations

• Relative motion
• CoM motion

9
Orbits
x
?a2.3
y
x
?a2.396
y
10
Average change in eccentricity of the protoplanet
as a function of ?a
11
?a
?a
12
Conclusion

• Determined eccentricity change for close
  encounters
• Results agree with G T (1980) for
• ?a gtgtRH
• Need to gain better understanding of spikes
• Finish calculation