ASTR109, Winter 2008
Here is a summary of what is going on in ASTR109 day by day. Use it to
help remind you of what you've learned or, if you need to miss a
class, as a study guide. If you have missed a class, be sure to get
notes from another student.
- Lecture #1. Details of how class is organized
(see Course Description and Lecture Schedule). Size and scale of the
Universe. Powers of Ten video (from YouTube). Introduction to the
ASTR109 website. Definitions of terms: Planet, Star, Moon, Asteroid,
Comet, Nebula, Galaxy, Galaxy Cluster, Local Group, Black
Hole. Relationship between stars and gas.
- Lecture #2. Speed of light, age of the Universe,
definition of a light year. Various motions of the Earth: rotation,
revolution around the Sun, Solar System's motion around the center of
the galaxy, the galaxy's motion. Constellations, the Celestial Sphere,
the Milky Way, Apparent motion of the stars across the sky.
- Tutorial: Week #1. Discussion of Earth/Moon
System, sizes and distances. Clues to Solar System formation - why do
planets orbit along nearly circular paths? Why do they all orbit in
nearly the same 2 dimensional plane? Why do they all go around the Sun
in the same direction? The properties are clearly not random. As we
learn about the Solar System, be alert for additional patterns - we
will use them to test theories for how the Solar System formed. Some
discussion of homework problems. Some discussion of magnetic fields
and Earth's molten iron core.
- Lecture #3. The cause of seasons on Mercury,
Venus, Earth, and Mars. Phases of the Moon. Rotation of the
Moon. Lunar and solar eclipses. The wandering stars. New terms:
midnight sun, equinox, solstice, umbra, penumbra, partial eclipse,
- Lecture #4. Importance of models in science. The
geocentric and heliocentric models of the Solar System. Circles and
Ellipses. Retrograde motion. Ptolemy, Copernicus, Brahe, Kepler,
Galileo. Kepler's 3 Laws. Earth in comparison to other terrestrial
planets. The Sun, Mercury. The effects of an atmosphere on day/night
- Tutorial: Week #2. Quiz #1 today! The quiz covers
topics from HW#1 and from all class meetings up to this point.
- Lecture #5. Atmospheres of Venus, Earth, and
Mars. Origin of Venus' Carbon Dioxide atmosphere. Temperatures on
Mercury, Venus, and Earth. Ice on Mercury? Sunlight heats planetary
surfaces. Atmospheres trap heat: the atmospheric greenhouse effect.
Thinning of atmospheres with height. Shapes of large and small Solar
- Lecture #6. Much of this material is covered on
the "Earth's Interior" website linked from the ASTR109 main page
Definitions of P & S waves and how we use them to probe Earth's
interior. Planetary differentiation and the formation of iron
cores. The interiors of Mercury, Venus, Earth, Mars, and the
Moon. Small bodies cool faster than large ones. Plate tectonics is
driven by mantle convection. What drives the convection? Oxygen in
Earth's atmosphere. Jupiter and its satellites.
- Tutorial: Week #3. More detail on the Earth's
Interior website. Earthquakes and Volcanoes. Mantle hot spots and the
growth of shield volcanoes (e.g. Hawaii). Seafloor spreading and the
age of seafloor rocks. Magnetic field reversals. The uniform young age
of Venus' surface.
- Lecture #7. Survey of the giant planet, their
main satellites and their ring systems. Pluto and Eris. Sources of
comets: the Kuiper Belt and Oort Cloud. Recap of clues in the Solar
System that hint at how planet formation works. The nebular theory:
collapse of a large cloud of dust and gas to form a flattened disk of
material. Coalescence of the planets from this disk. Link to a similar
disk of debris: Saturn's rings.
- Lecture #8. Formation of the Solar
System. Collapse of a giant gas cloud, which spins faster, flattens
out, and heats up. The spinning chair of DOOM class demo! Prof. learns
that our class has only one brave volunteer. Growth of dust grains to
km-sized planetesimals to 1000-km-sized protoplanets. Giant collisions
in the end stages are responsible for Earth's Moon and Mercury's large
iron core. Lots of collisions is consistent with the heavily cratered
surfaces that we see all over the Solar System. Similarities between
planet formation and satellite formation. Explanation for
terrestrial/giant planet dichotomy. Why Jupiter is largest of all the
- Tutorial: Week #4. Quiz #2 today! The quiz covers
topics from HW #1-3, Quiz #1, and from all class lectures and tutorials
up to this point. Starting HW #4 early might also help you.
- Lecture #9. All about the Sun. What is it made
of? How do we know fusion of H to He powers it? Structure of the Sun:
Corona, Chromosphere, Photosphere, Convection Zone, Radiative Zone,
Core. Gravitational Equilibrium. Radiative Equilibrium. Temperature
inside the Sun. Fission vs. Fusion. Why high temperatures are needed
for fusion. How the Sun regulates its internal temperature.
- Lecture #10. Other stars. Open and Globular Star
Clusters. Spectra of stars. Thermal radiation. Absorption
lines. Behavior of material with temperature. How we can measure
temperatures and compositions of distant stars. The largest and
smallest stars. The brightest (most luminous) and dimmest stars. The
HR diagram. How we measure stellar sizes (radii). The main
sequence. Stellar lifetimes. Giants and Dwarfs.
Tutorial: Week #5. How to solve Moon Problems! See
example problem under "Quizzes" on the Assignments page. Properties
of Ellipses. Earth to Mars transfer orbits.
- Lecture #11. High mass stars explode as
supernova. Hydrogen balloon demo. Giant stars have finished burning
hydrogen in their cores. White Dwarfs have finished all their nuclear
burning. Low mass stars create planetary nebula from low-speed
winds. Inside every planetary nebula is a white dwarf. Creation of the
elements in the periodic table. If lighter than iron, formed in
stars. Heavier than iron, formed in supernovas. Fusion can extract
energy from light elements, fission extracts energy from heave
elements. Iron is the most stable element and no energy can be
extracted from it by fission or fusion.
- Lecture #12. White Dwarfs, Neutron Stars, Black
Holes. White dwarfs are Earth-sized and are supported by relativistic
electrons: "electron degeneracy pressure". More massive white dwarfs
are smaller in size! Most massive white dwarf is 1.4 Solar
masses. Add a bit more mass and they explode as supernovas! So there
are two types of supernovas: a "white dwarf supernova" and a "massive
star supernova". In massive star supernova, a compact remnant object
is left behind (a 10-km neutron star for large stars or a black hole
for the very largest stars). White dwarf supernovas blow the object to
bits and leave no small remnants behind. Neutron stars rotate rapidly
and have large escape velocities. Some beam radiation and are seen as
pulsars. The rotating radiation beam from a pulsar is like the light
beam from a lighthouse. Neutron stars are supported by neutron
degeneracy pressure - most massive neutron star is 2-3 solar masses.
If more massive, it would collapse to a black hole. Event Horizon is
the point where the escape speed is the speed of light. From within
this zone, nothing can escape. Black holes warp space and time in
- Tutorial: Week #6. Quiz #3 today! The quiz covers
topics from HW #1-5, Quizzes #1 and #2, and from all class lectures
and tutorials up to this point. It will have a very strong emphasis on
stars (lectures 9-12).
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