This is one of a series of notes taken during the 2015 meeting of the AAS Division on Dynamical Astronomy, 3-7 May, at CalTech. An index to this series (all the papers presented at the meeting) is here.
Session: Exoplanet Theory I
Ruth Murray-Clay (UC Santa Barbara) (invited)
Abstract
[none]
Notes
- How do giant planets and brown dwarfs form?
- Architecture of Solar System is atypical.
- Lots of gas giants at large distances, small distances (“hot Jupiters”), but not much in between a la Solar System. Why?
- SS: rocky planets (~1 AU), gas giants (~5-10 AU), ice giants (~20-30 AU)
- Theory: cannot predict numbers, but can predict patters in system architectures and statistical populations
- How to get companions to stars: 1) turbulent fragmentation, 2) grav. instability, 3) core accretion
- HR8799: testbed for planet formation theories
- 4 Jupiter-mass planets
- turbulent frag.? No: system is not hierarchichal
- grav. inst.?
- iffy – minimum fragment distance problems (but could have migrated)
- Timing – collapse must occur at end of infall or a binary star results
- core accretion?
- dynamical (growth) timescale is too long ($t_{grow} > t_{infall}$)
- $t_{grow} > t_{disk}$
- cross section regimes — all problematic:
- physical cross section
- grav focusing
- gas drag capture
- Make gas useful.
- no gas: particles can orbit inside core Hill radius
- gas: “wind shear”
- binary capture
- particle capture can occur out to Hill radius
- growth time at 70 AU can be short enough to nucleate an atmosphere
- turbulent gas: okay
- accretion cross sections increase by up to $10^4$
- Gemini Planet Imager could confirm this theory.
- Metal-rich stars hostmorehotJupiters and highly eccentric planets: signature of planet-planet interactions? Why?
- Scattering?
- Secular chaos?
- Perhaps those systems form many Jupiters.
- Are the solar system analogs orbiting low metallicity stars?