I. Cloud Collapse:
A huge (many light-years) cloud of gas and dust collapses.

II. Thin dust disk:
A gas/dust disk forms around the growing star because of angular momentum conservation.

The dust settles into the mid-plane of disk.

III. Planetesimal Formation:
Objects 1-10km form via gravitational collapse.

IV. Proto-Planet Formation:
Planetesimals collide to form proto-planets. These are roughly the size of the Moon at 1AU.

• Unter-planets form at this time.

V. Solid Planet Formation:
Proto-planets collide with each other and leftover planetesimals to form: a) the terrestrial planets, b) ice giant planets, and c) the cores of the gas giants.

VI. Gas Giant Formation:
In regions where big objects grow large enough (~10X mass of Earth) before the gas dissipates, they will accrete gas directly. This forms the gas giants (Jupiter and Saturn).

• Giant planets can move a lot at this time.
• Probably the cause of the 'Hot' Jupiters.

VII. Dynamical Redistribution:
Dynamical instability of orbits can led to planets moving around. Probably caused the high eccentricity extra-solar planets.

Also, probably happened to Uranus and Neptune.

Stage I

Stage II

Stage III

Stage IV

Stage V

Stage VI

Stage VII

.............................................................................. ...............................................