Orion Nebula: Star-forming Region

Solar Nebula

Flattening the Solar Nebula

Disks Around Other Stars

Steps in Planet Formation 1.Condensation 2.Accretion 3.Nebular Capture (Jovian Planets only) After planets form, the solar wind clears the nebula: gas and dust are blown away

Condensation and Temperature Metals: iron, nickel, aluminum, and other metals can solidify around 1600 K Rocks: primarily silicon-based minerals solidify around K Hydrogen Compounds: molecules of methane, ammonia, and water freeze into ices below 150 K Light gases: hydrogen and helium never condense in the solar nebula

Accretion into Planetesimals Condensed materials collide and stick together forming planetesimals Planetesimals would continue to grow from further accretion and gravity Larger planetesimals would form spherical shapes because of stronger self-gravity Some planetesimals would fragment due to collisions

Planetesimals to Planets

Self-gravity

Uncompressed Densities

Nebular Capture: Jovian Planets Larger planetesimals of the Jovian planets resulting in a stronger gravitational force Stronger gravity allowed the Jovian plantes to capture more gas and planetesimals Hydrogen and Helium gas could be captured despite low mass of these gases Jovian planets formed disk-shaped nebulae Lower temperatures meant Hydrogen and Helium gas would not escape from the Jovian planets

Nebular Capture: Jovian Planets

The Sun’s Lost Spin Magnetic field of the Sun drags charged particles in the disk of the solar nebula. This causes friction which slows down the rotation of the Sun Otherwise, the Sun should have a faster spin than is observed

A History of Impacts

Captured Moons of Mars

Leftover Planetesimals

Radioactive Dating

Detecting Extrasolar Planets

Extrasolar Planets

More Extrasolar Planets

First Direct Detection! Planet Orbiting the star HD Eclipsed by planet