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Review for Test 1
AST. 309L - REVIEW OF CH. 1 - 3D
- Basics
Typical dimensions in universe, common structures
Definition of life - traditional (5 attributes) and more abstract
Chemical composition of life, and relative to earth/universe
The Drake Equation, metric system, absolute temp. scale
- Origin of atoms
- Before stars
- Elementary particles and the Big Bang
- Four fundamental forces - gravity, electromag., strong, weak
- Nuclei after 3 minutes (H 75%, He 25%), atoms after several x 100,000 yrs
- Galaxies and stars formed from gravitational instabilities
- Velocity of a particle in a gas, depends on T and m.
- Nuclear reactions in stars
- Potential energy diagrams
- Repulsion of like charges creates "barrier" to climb for nuclear strong force
- Conversion of mass into energy
- H into He via p-p cycle (later in more massive stars, CNO cycle)
- "Triple alpha" process makes C via route using unstable Be
- Adding another He nucleus makes O
- Heavy elements made at high T, in massive star centers; and SN (beyond iron)
- Origin of molecules and planets
- Chemical interactions (reactions)
- Potential energy diagrams; chemical bond = shared electrons, EM force
- Activation energy barrier, due to electron repulsion
- No energy barrier present for ion-molecule interactions
- Molecules and dust in space (dust is about 1% by mass, but important)
- Many molecules found in space, high % have carbon; C in long chains even
- Molecules found by radio emission from rotational energy changes
- Molecules and dust found together; PAH's are like large mol, or small dust
- Dust comes from old stars; both silicate and carbonaceous dust
- "Ice" mantles on grains where cold; possible chem. reactions
- Dust protects molecules from UV, provides site for making H2
- Molecular clouds, range of sizes and masses, produce stars
- Star formation - R(*)
- Rate calculated from # stars in galaxy and life of galaxy (corrections
for stars that are already dead, and if rate not constant)
- Theory: inside collapses first, disk forms for more matter to accumulate
- Massive stars form and evolve much faster than low mass stars
- Disks inferred from bi-directional winds, from large amount
of dust seen in infrared together with not-obscured stars, HST images
- Disks a natural consequence of angular momentum of parent cloud
- "Stars" that don't burn H are "brown dwarfs", more mass than planet
- Planet detection - f(p)
- Detection of planets very difficult, wobbling in space or velocity
most likely detection methods; direct observation very difficult because
of resolving power, infrared better than visible but still too hard
- Virtually all detected planets (~ 30) seen by periodic velocity change of star
- Properties of our solar system are consistent with disk formation
model, so maybe many planets exist since we see so many disks
- Detected planets heavily influenced by detection method - massive and close to star
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