Transcript The Diversity of Extrasolar Terrestrial Planets J. Bond, D. Lauretta & D.

The Diversity of Extrasolar
Terrestrial Planets
J. Bond, D. Lauretta & D. O’Brien
IAU Symposium 265
14th August 2009
Chemistry meets Dynamics
• Most dynamical studies of planetesimal formation have
neglected chemical constraints
• Most chemical studies of planetesimal formation have
neglected specific dynamical studies
• This issue has become more pronounced with studies of
extrasolar planetary systems which are both dynamically
and chemically unusual
• Combine dynamical models of extrasolar terrestrial
planet formation with chemical equilibrium models
of the condensation of solids in the protoplanetary
nebulae
Dynamical simulations reproduce
the terrestrial planets
• Use very high resolution n-body accretion simulations of
terrestrial planet accretion (e.g. O’Brien et al. 2006) for
10 known extrasolar planetary systems
• Incorporate dynamical friction
• Start with Mars-mass embryos located interior to the
known giant planets. All known planets are assumed to
be in their current orbits
• Neglects mass loss
Equilibrium thermodynamics predict
bulk compositions of planetesimals
• Use spectroscopic photospheric abundances of 16
elements: H, He, C, N, O, Na, Mg, Al, Si, P, S, Ca, Ti, Cr,
Fe, Ni
• Assign each embryo a composition based on formation
region
• Adopt the P-T profiles of Hersant et al (2001) at 7 time
steps (0.25 – 3 Myr)
• Assume no volatile loss during accretion, homogeneity and
equilibrium is maintained
Solar System Testing
• “Ground tested” on Solar System simulations of O’Brien
et al (2006) – good agreement
• Volatile enriched
• See Bond et al (2009) Icarus
Extrasolar “Earths”
• Terrestrial planets formed in ALL systems studied
• Most <1 Earth-mass within 2AU of the host star
• Often multiple terrestrial planets formed
• Migration may alter some of these simulations . . . stay
tuned!
Extrasolar “Earths”
• HD72659 – 0.95 MSUN G star, [Fe/H] = -0.14
• 3.30 MJ planet at 4.16AU
• Gl777A – 1.04 MSUN G star, [Fe/H] = 0.24
• 0.06 MJ planet at 0.13AU
• 1.50 MJ planet at 3.92AU
• HD108874 – 1.00 MSUN G star, [Fe/H] = 0.14
• 1.36 MJ planet at 1.05AU
• 1.02 MJ planet at 2.68AU
HD72659
HD72659
• 1.03 MEarth at 0.95AU
Gl777A
Gl 777A
• 1.10 MEarth at 0.89AU
0.27 wt% C
HD108874
HD108874
• 0.46 MEarth at 0.38AU
66 wt% 27
C wt% C
HD108874
• 0.47 MEarth at 0.38AU
HD108874
SiC
Gl777
SiO
MgSiO3 +
SiO2
HD72659
MgSiO3 + Mg2SiO4
Mg2SiO4 +
MgO
Terrestrial Planets may be very
different in ESP systems
• Terrestrial planets may be common
• Geology of these planets may be unlike
anything we see in the Solar System
– Earth-like planets
– Carbon as major rock-forming mineral
• Composition varies with ‘primordial’
chemical enrichments
• Implications for detection, planetary
processes, atmospheric composition . . . .