Origin of Solar System

Lecture 15

Key Properties of our Solar SystemAny theory of the origin of the solar system must be able to explain following key

properties in the simplest manner.1. Sizes and compositions of terrestrial planets versus Jovian planets2. Direction and orientations of planetary orbits3. Sizes of terrestrial planet orbits versus Jovian planet orbits

There are 103 elements known to exist.Yet, all known life forms are mainly based on C, H, O, & N, and most advanced

organisms are using H2O! Why?Why shouldn’t there be life forms with iron skeleton and using methanol?

Origin of the ElementsAfter Big Bang, lightest elements (H, He, Li, Be) were created, but only for a limited time period (3 to 20 minutes).

92% H + 8% He and almost no other elements.

Creation of the Elements(Nuclear Synthesis)

Hydrogen “burning” = the main energy source of stars over long, long time (e.g., for Sun, 10 billion years).

Hydrogen burning : 4 Hydrogens Helium + energy

US yearly energy consumption:1.107×1020 Joules= can light Sanford stadium for 100

billion years!= can be produced from a fusion of

mere 80lb of Hydrogen!

Cosmic abundance

Later stages of Nuclear fusions in StarsNot much Li (H+He), Be, B (Be+H or He+Li)…

Lots of clouds in the Galaxy

Angular Momentum Conservation

Spinning sphere Spinning Figure Skater

Formation of Planetary System (nebular theory)

Contraction and disk formationOnce the collapse begins, nebula would heat up, spin faster, and flatten…

Conservation of Energy (heating up) : gravitational potential energy heat energyConservation of angular momentum (spinning up)

collapsed to a nearly 1/1,000,000 of the initial size

Composition of Clouds

Formation of Planetary System

Condensation (opposite of melting) : High temperatures in the inner region materials only with high condensation

temperatures can turn to solids (metals and rocks). Outer region is much cooler materials with lower condensation temperatures can

turn to solids also (ices, rocks and metals) more solids than the inner region!Hydrogen and Helium remain as gas everywhere in the disk.

Formation of Planetary System

Accretion of solidsPebbles rocks boulders … planetesimals (~100 km size)… this process over a few million years…

Collisions b/w planetesimals (some stuck, some shatter)

Formation of rocky planets (inner) and some ice-rocky planets (outer) Gas accretion in the outer area (why not inner?) Jovian planets!

Formation of Planetary System

Moon formations around Jovian planets in a disk surrounding a Jovian planet (similar to the way planets are formed)…

Formation of Planetary System

Clearing the DiskRemaining gas will be blown away by solar wind…

Rocks remain, but gradually being cleared by planets or collide among themselves…

Is this happening at other stars?

Young stars in their early formation showing a disk (dark shade)

Y E S !

Planetary system formation simulationhttp://www.youtube.com/watch?v=jhYEQgLW5NM

In summary…

Important ConceptsPlanet formation (nebular

hypothesis)Conservation of EnergyConservation of angular

momentumOrdered structure of planets is a

natural outcome of planet formation.

Important Termscosmic abundancesolar nebulacondensationprotoplanetary disk

Chapter/sections covered in this lecture : sections 8-1,8-2, & 8-4