PX282 - L1 - nebular hypothesis

image: R. Townsend, UCL

following the gravitational collapse of gas in a molecular cloud, and the conservation of angular momentum, a proto planetary disc is formed around the young sun
this explains why all the planets are orbiting in the same plane and are aligned with the spin of the sun
the minimum mass of the solar nebula can be estimated by spreading out the planets and topping up to solar composition:

Σ (r) \propto r^{- 3 / 2}

where, $Σ$ is the surface density of the disc ([kg m $^{2}$ ])

M_{d i s c} \geq 0.01 M_{⊙}

assuming that the gravitational potential energy is radiated locally in the disc:

T_{d i s c} \propto r^{- 3 / 4}

image: Hayashi (1989), D. Forgan

the amount of solid materials increases drastically beyond he snowline, although still lower than gases
this forms the boundary between the terrestrials and the giants
the lifetimes of protoplanetary discs around young stars $\sim 10^{7}$ years

image: IAU