Review Sheet: Test 2
Date of Exam: May 8, 2009
Version Date: May 7, 2009--I removed some information about star formationa nd
stellar
evolution. I got into the STAR FORMATION section on
Wednesday.
Material: Class notes, Web notes, and relevant parts of
primarily Chapters 16 & 17; not much (if anything) from Chapters 18, 19.
Please check and use your class notes to determine how far to cover in
the webnotes and the text.
Formulas:
- Blackbody Laws:
- Wien's Law -- The wavelength at which a blackbody appears the
brightest is inversely proportional to the temperature of the
blackbody, i.e.,
- Stefan-Boltzmann Law -- The power radiated per unit area from a
blackbody is proportional to fourth power of the temperature, i.e.,
- Flux from a star at distance, D:
- Luminosity of a star of temperature T and radius R:
- Lifetime of a Main Sequence Star with mass M > 0.7 Solar Masses:
lifetime = [M/(Mass of Sun)]-31010 years
Old Test from an earlier time I taught
ASTR 122. Beware that depending on the year,
the rate at which material is covered varies.
Topics:
STELLAR PROPERTIES
- What are Main
Sequence Stars, giants (Red Giants), Super-Giants, Asymptotic
Giant Branch (AGB) stars, white dwarfs, planetary nebulas?
- What is the range of Main Sequence stars in terms of their mass?
- What is the Mass-Luminosity relation? How can it be used to infer a
scaling law for stellar lifetimes?
- What kinds of stars are the most numerous? High or Low luminosity stars?
- All stars on the Main Sequence must obey which two equilibrium laws?
What are these laws?
Poperties of the Sun:
- What is the Solar Activity Cycle? Rouhgly, suggest a simple way through
we can understand how the Solar Activity Cycle works (the differential rotation
of the Sun and the magnetic field of
the Sun play large roles in this process).
- What is meant by the Quiet Sun? What is meant by the active Sun?
- Describe the appearance of the Quiet Sun and list its properties. What are
the properties of the photosphere, the chromosphere, the corona? Why is the
Corona hotter than the Photosphere? What is the transition region? What is
granulation? What causes granulation?
- What are sunspots? What are the umbra and the penumbra of a sunspot?
How many times brighter is the surrounding Solar photosphere than the umbra
of a sunspot? What are plages? How long do sunspots live, on average? What
about sunspot groups?
-
What are quiescent and eruptive prominences? What is the Solar Wind? What are
coronal holes?
What are filaments? What are flares? How are flares classified?
What are CMEs? What effects do flares and CMEs have on the Earth?
What property of the Sun seems to unite all the phenomena of the
Solar Activity Cycle? roughly, describe the mechanism which is though to
drive the Solar Activity Cycle. The Sun is in differential rotation. What
does this mean?
- What is the period of the solar activity cycle? Is this the same as
the period for the variation of the number of sunspots visible on
the surface of the Sun? What is the Butterfly Diagram?
What is the Maunder minimum? What is the significance
of the Little Ice Age which struck Europe in the mid 1600s (in
terms of Solar variability)? Roughly, how large
is the variation of the Solar power
(Solar constant) over a Sunspot cycle. Are
there noticeable effects of this variation on the climate of the Earth?
Theoretical Properties of the Sun and Stars:
- What are the different ways discussed in class that
stars can generate energy? What is the most efficient way to generate
energy of those mentioned in class? What mechanism is used by Main Sequence
stars to generate energy? What physical concept underlies
the famous Einstein result that E =
mc2?
- Nuclear Energy Generation--the
conversion of 4 hydrogen nuclei into a helium nucleus + energy + other
particles. What are neutrinos? Why is
nuclear fusion so difficult (that is, what is the major impediment to fusion)?
- What is the proton-proton cycle (pp-cycle)? What is the
carbon-nitrogen-oxygen cycle (CNO cycle)?
- How can fission and fusion both generate energy?
In this context, why is iron such an important
elemnet? Since fusion and fission can both generate energy, does it then
follow that nuclear reactions are a source of unlimited energy?
- What are the energy transport mechanisms used by stars? Which ones are
the most important for the Sun?
- What important role outside of energy transport does convection play in
the observable properties of the Sun?
- Why is qunatum mechanical tunneling important for stars? What is the
Heisenberg Uncertainty Principle? Compare and contrast matter and
anti-matter.
What is annihilation? What is the matter/anti-matter asymmetry
problem?
- Main Seqeunce stars are in equilibrium;
both mechanical equilibrium (hydrostatic
equilibrium -- stars are not changing in size very quickly) and thermal
equilibrium (the temperature structures of stars are not changing
very quickly --
the energy losses due to radiation and particles from
stars are roughly balanced by the energy production due to
nuclear fusion reactions).
- Hydrostatic Equilibrium -- We need to address what holds
stars together (gravity), and to address what keeps stars from
collapsing into dense balls (gas pressure).
- Thermal Equilibrium --We need to address the energy source for
stars and how stars lose energy.
- Why are neutrinos so much useful as probes of the interior of the
Sun than are photons (the light we receive from the Sun)? What other
methods are used to probe the interior of the Sun? What was the
Solar Neutrino Problem? How was the Solar Neutrino Problem resolved?
STAR FORMATION
- Write down the expression from which we estimated the lifetime of
the Sun on the Main Sequence. How much of the Sun's initial amount of
hydrogen is used while the Sun is on the Main Sequence?
- Write down the expression which relates the Main Sequence lifetime of
a star and its mass. Estimate the ages for stars with masses 50 times the
mass of the Sun, 10 times the mass of the Sun, and 0.1 times the mass of
the Sun.
- Is star formation an ongoing process in our Galaxy?
How do we deduce whether or not
star formation is an ongoing process? Will the star
formation process continue forever? Describe how we arrive at the answers
to these questions.
- What is nucleosynthesis? What is the most massive element made in
normal stellar evolution? In what nuclear burning stage is the Sun?
- What forms of energy transport are important for stars?