MULTIPLE CHOICE
---------------

1. Helium flash happens
(a) in low mass stars as they form and become Main Sequence stars
(b) in high mass stars as they become Red Giants
(c) in low mass stars during their Red Giant stage of evolution
(d) when high mass stars begin to fuse Silicon into Iron in their cores
(e) when low mass stars begin to fuse Helium into Iron in their cores

2. Which one of the following is NOT a byproduct of nuclear 
fusion in the core of Sun?
(a) photons
(b) neutrinos
(c) Iron
(d) Helium
(e) all of the above

3. If the orbit of a binary star system lies exactly in the plane of the 
sky (so neither of the two stars ever blocks the other), then we cannot measure
(a) orbital velocity of the two stars 
(b) temperatures of the two stars 
(c) chemical composition of the photospheres of two stars 
(d) apparent brightness of the two stars 
(e) any property of either of the two stars

4. The Helium burning stage in the life of the Sun will be ________
    than the Hydrogen burning stage because _________
(a) shorter; Helium is a less efficient fuel compared to Hydrogen
(b) longer; Helium is a less efficient fuel compared to Hydrogen
(c) shorter; Hydrogen is a less efficient fuel compared to Helium
(d) longer; Hydrogen is a less efficient fuel compared to Helium
(e) same; Hydrogen and Helium have the same fuel efficiency


SHORT ANSWER
------------

1. Briefly explain why Earth's atmosphere contains less CO2 than Venus's

2. Explain how the greenhouse effect makes a planet's surface warmer than
it would be otherwise.

3. Name two sources of internal energy for Terrestrial planets. What additional
source of internal energy do Jovian planets have? 

4. Explain why thermonuclear reactions in stars require high temperatures
to proceed.

5. Explain why sunspots are look different from the rest of the Solar surface?

6. Explain why (at any given time) most of the stars are on the Main Sequence
of the HR diagram.

7. Explain why stars eventually leave the Main Sequence. How do their
properties change just after they leave the Main Sequence?

8. Will the Sun become a Supernova in the future? Why?

9. Where did Silicon and Iron in the Sun's photosphere come from?


MIDTERM II TOPICS (Chapter 7-12)
--------------------------------

Terrestrial/inner planets: sources of internal energy
Atmospheres of terrestrial planets: relative amounts of CO2, H2O
Greenhouse effect
Where did Nitrogen in Earth's atmosphere come from?
Where did water come from?
Habitable Zone
Jovian/Outer planets: composition, structure
Satellites, ring systems
Debris in the SS: asteroid belt, Kuiper belt, Oort cloud of comets
Comets vs. asteroids; properties
The Sun:
Hydrostatic equilibrium: gas pressure vs. gravity balance 
Thermonuclear fusion reaction in the core: H-->He (proton-proton chain)
Neutrinos; properties; detection
Transport of energy within the Sun: convection
Surface layers:  photosphere, chromosphere, corona, solar wind
Magnetic field: 22 year cycle, loops and sunspots
Stars: 
Strength of Hydrogen spectral absorption lines and surface temperature
Measuring distance to stars:  parallax
Measuring radii of stars: from luminosity and surface temp & using binaries
Measuring masses: from binaries and Kepler's 3rd law
Hertzsprung-Russell (HR) diagram: Luminosity vs. surface temperature
Main sequence; relation to mass of star
Evolution of star cluster on the HR diagram; star lifetimes
Star clusters: open vs. globular
Minimum mass of a star; brown dwarfs
Evolution of low mass stars: core, shell nuclear fusion, Helium flash,
                             red giants, planetary nebula, white dwarfs
Evolution of high mass stars: successive core, shell fusion of elements,
                              red giants, supernova, neutron star, black hole
Why Iron is special among elements; fusion vs. fission
Chemical enrichment
Supernova Remnants