• For Quiz 4 on Wednesday Oct 25th
• 5 questions from material for Quiz 3, 10 from material below
• Read the textbook - particularly chapter 8 (chapter 6 for quiz 3 material)
• Go through sessions 10 & 11 on the website - check answers under "self-study"
• check understanding of concepts, not just definitions but how things work.
• Go to the review sessions on Mon 6.30-8.30 (optional)
• See answers to Quiz 3 on the web.

Four Challenges - Table 8.3 pp 211-216.

You DO NOT need to know any planetary facts - DO NOT memorize Table 8.1

DO learn Tables 8.2 and 8.3 (in your own words)

Where does the star- and planet-forming material come from?

Sequence for collapse - Figure 8.6

Collapse under self-gravity

Contraction -> heats up

-> spins up (conservation of angular momentum p 141)

collisions -> disk - fig 8.7

condensation of material according to temperature p220

Metal & rock in inner solar system

Metal & rock & ICE in outer solar system - beyond "frost-" or "snowline"

Accretion of flakes -> balls -> bigger balls -> planetesimals

Planetesimals collide -> accrete to planets

-> fragments (asteroids, comets)

Inner solar system - smaller, rocky planets too small for gravity to hold in hydrogen

Outer solar system - BIG "snowballs" of ice and rock beyond the "snowline" have strong enough gravity to hold in hydrogen - most abundant element - to make GAS GIANT PLANETS.

From radioactivity dating pp 229-30

Ratio of [argon-40/potassium-40] found in rock is proportional to the age of the rock

(->0 for young, ->1 for old)

Dozens of planets being detected around other stars

Detected by gravitational perturbations of the central star ("sun") by large (Jupiter-sized) planet close to the star.