The Birth of Giants â Bottom Up or Top Down?
Gravitational Instability Gravitational Instability (GI) Dispersion relation for density waves in disk Get and instability when Toomre Q parameter Objects with size and mass form, with roughly equal thermal, gravitational and rotational energy contributions. Collapse further if thermal and rotational support can be removed.
Gravitational Instability Mayer et al. 2002 TreeSPH, isothermal EOS, Pros: • allows planets to form quickly ( • explains potentially coreless extrasolar planets • explains distant planetary companions Cons: • does not naturally explain cores (and high-Z element enhancements) of Jupiter and Saturn yr) • does extremely poor job accounting for the cores of Neptune and Uranus • requires extremely massive protoplanetary disks : between 4 and 20 AU (typical observed disk masses are within 100 AU)