Astronomy 340 Fall 2005 27 October 2005 Class

Astronomy 340 Fall 2005 27 October 2005 Class #? ? ?

Asteroids Phobos Ida

Asteroid Distribution - orbit n n n Note concentrations in various regions of the plot Each clump is an asteroid “family” Major families q q q Main belt (Mars-Jupiter) Trojans Near-Earths

Distribution – SDSS results 200, 000 asteroids – Ivezic et al. 2002

Size Distribtion n Power law N(R) = N 0 (R/R 0)-p n n Theory says p = 3. 5 based on collisionally dominated size distribution Ivezic et al. 2000 p=2. 3 +/- 0. 05 for size distribution of 0. 4 -5. 0 km main belt asteroids q Derived from SDSS data

Collisions n Collisions numerical simulations q n 100 -200 km diameter progenitors Limits? q q Surface ages Vesta’s surface looks primordial, but it has a large impact crater

simulation

Asteroid Composition n How do you measure asteroid compositions? q Reflection spectroscopy Comparison with meteorites

Asteroid Composition - colors Jedicke et al. 2004 results indicate “space weathering”

Comparison with meteorite samples Points are real data, line is reflection spectrum of sample

Composition-results n 75% of asteroids are dark q q Look like “carbonaceous chondrites” Most of these are “hydrated” heated in past so that minerals mixed with liquid water n 12% are “stony irons” Fe silicates M-type albedos pure Ni/Fe, no silicate absorption features n …and now onto giant planets… n

Giant Planets – issues n Basics q Interior structure (is there something solid? ) n n q q Composition – deviations from solar? Atmospheric physics n n q Ring systems Extensive satellite systems Cool Moons q n What accounts for the colors? Can the giant planet systems be considered “mini-solar systems? ” q n Sources of heat Magnetic fields Io, Europa, Titan, Triton Formation q q How long does it take to form a gas giant? How did they get there?