The Formation of the Solar System

Planetary motions The Sun, planets, asteroids, comets, planetesimals all revolve in the same direction with some exceptions. Rotation axes usually perpendicular to orbital plane

Pluto

Planet-Planetesimal composition Terrestrial Planets: Cores  Small & rocky (refractory elements, silicates & iron) Atmospheres: Thin, no H/He, some ices or volatiles (C, N, O, Ne) Jovian Planets: Cores  large rocks/metals/ices Atmospheres  H or H-compounds (e.g. CH 4 ) KBOs: planetesimals and icy bodies: Small ice & rock mixtures with frozen volatiles.

Icy Pluto Giant Gas Planets Mostly H, He, & Ices Rocky Planets

Gas cools and condenses gravitationally into a disk Primordial Gaseous nebula

Proto-Planetary Disks and Star Formation

Primordial Solar Nebula Rotating solar nebula is composed of ~74% Hydrogen & 25% Helium Traces of metals and dust grains Initially T~2000 K, gas cools to ice and dust according to condensation temperature

Condensation Temperatures T(K) Elements Compounds (oxides,silicates) >2000K gases Ions: atoms, molecules 1400K Iron & Nickel Metal Grains (e.g. Fe 2 O 3 ) 1300K Silicon, Sulfur Silicate grains 300K Carbon Carbonaceous grains K H, C, N, O Ices (H 2 O,CO 2,NH 3,CH 4 )

Snow Line: Separation of Rocks/Metals from Gases/Ices Rock & Metals form where T < 1300 K Carbon grains & ices where T(gas) < 300 K Inner planets and asteroids: Rocky and metallic Snow line Outer Jovian systems: Gaseous giants, carbon ices Dust grains and ices collide, accrete, and eventually grow bigger gravitationally into planetesimals beyond the snow line

Life of the Sun Burns or converts H  He via theromonuclear fusion in core When hydrogen in the core is exhausted, converted into helium, the H-burning shell moves outward and the star expands H-burning phase for another 5 billion years; inert He-core Stars in H-burning phase are said to be Main Sequence stars Sun  Red Giant Eventually He in the core ignites  helium flash He-burning  C/O (carbon, oxegen core) Core separates from the envelope, which is ejected Hot core and ejected envelope  “Planetary Nebula” (star looks like a ring with bright center; nothing to do with planets) Central core of planetary nebulae cools  White Dwarf

Red Giant Star Inert He Core H Burning Shell Cool, Extended Envelope

Planetary Nebulae Sampler

Death of the Sun Hot core continues as a white dwarf, about 60% mass of the Sun and size of the Earth Gigantic diamond in the sky!

The Death of the Sun