Test 1
Date of Exam: 6 August 2009
Review Version: 3 August 2009

In the following, I list the topics covered in class and information which I consider important to know. I tried to make the list as complete as possible, but there may be things which I have inadvertently failed to list. Also, the precise amount of material to be tested is determined by how far I get through the notes by the end of Tuesday, August 4, 2009. I will adjust the review sheet after class tomorrow.

Reading: First, read and study your class notes and then the Web notes. If you wish, the text may be used rather than the web notes. There is no replacement for the class notes. Your class notes will help you to focus on things which I consider to be the most important and note that the introduction was drawn from various parts of the text and from other independent sources. There are also sometimes things said in class which may not appear in the Web notes and/or the text for which you are responsible.

Old Test

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.,
    W = 0.3 cm-K / T(K)
  • Stefan-Boltzmann Law -- The power radiated per unit area from a blackbody is proportional to fourth power of the temperature, i.e.,
    Flux = constant x T⁴

• Inverse Square Law: Flux (brightness) depends on the distance from the star as:
  Flux is proportional to 1/D²)

• Luminosity of a star of temperature T and radius R:
  L = 12.6 constant R² T⁴

Topics:

Introduction

• Why do we study stars? What are the things which make astronomy a difficult experimental science? What makes the understanding of stars interesting, beyond the intrinsic value of having knowledge for knowledge's sake?
• In what ways do stars serve as physics laboratories? What are neutrinos? What are the Super-K and SNO experiments? Ten years ago, we thought that there was a lack of Solar neutrinos, how has our viewpoint changed? What have we learned about neutrinos as a result of the Solar Neutrino Experiment?
• What is nucleosynthesis (element production)? What does it have to do with stars and the Earth?
• How does the Sun generate energy? What are the documented Solar-Terrestrial Connections? What is the Solar Activity Cycle? What is the Maunder Minimum? When was 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? What is the Faint Young Sun Problem? What is the Equilibrium Temperature in the context of the Faint Young Sun Problem?
• How do we study stars? What are the most important ways which we use to study stars (e.g., light, particles, ...)? Historically, what has been the most useful method to study stars? Why?
• What is electromagnetic radiation? Physically, what is EM radiation? What is meant by electromagnetic spectrum? What are the parts of the electromagnetic spectrum in order of increasing frequency? What are the parts of the electromagnetic spectrum in order of increasing wavelength? What parts of the electromagnetic spectrum penetrate the atmosphere of the Earth?
• Define wavelength and frequency. How are they related to the energy of light? Which has the longer wavelength, blue or red light? How do the propagation speeds of blue light and red light compare?
• What is seeing? What were the principle advantages of the Hubble Space Telescope? That is, what were the advantages gained by placing a telescope into orbit about the Earth?

Stellar Properties:

• What are the ranges for the properties of stars? (what is the most important property of stars we mentioned in class?)
• How do we determine radii, masses, temperatures, and luminositites of stars? What is the hardest part of determining the luminosities of stars?
• What is the difference between flux and luminosity? Of flux and luminosity, which determines how bright an object appears to us (an observer on Earth?)
• What are the three kinds of spectra usually encountered in astrophysics?
• How are stellar spectra formed? What are Kirchhoff's laws of spectral formation?
• What information can be extracted from spectra (from both continuous and absorption line spectra)? How is information extracted from spectra? Consider how atoms are put together (what are electons, protons, and neutrons), why does the line spectrum serves as the fingerprint of an element, and how the different spectral features (continuous emission, line emission, absorption lines) are formed.
• Briefly, describe the structure of an atom. What are the main constituents of an atom? What property of an atom determines the type of element an atom is? What force holds an atom together? Roughly sketch the energy level diagram for a hydrogen atom. On your diagram draw arrows to indicate an absorption process, an emission process, an ionization process, and a recombination process. Draw another energy level diagram for hydrogen and then indicate the Lyman, Balmer, Brackett, and Pfund transitions.
• What is the Morgan-Keenan (MK) spectral classification scheme? How are spectra classified? (What criteria are used to classify stellar spectra?) Why do different stars have different appearing spectra? Explain why the strength of the hydrogren lines change as you go from O --> M.
• What important stellar property is carried by the spectral class of a star?
• What are the Luminosity Classses? For what types of star do the symbols I, III, and V stand?
• What is a blackbody? Give an example of a blackbody? What is the most perfect blackbody known? What characeristic of a blackbody determines its properties? What are the Wien Law and Stefan-Boltzmann Law? Which blackbody law is used (and how is it used to determine stellar temperatures)? Why are blackbodies interesting and useful idealizations for astronomers? How does the color of a blackbody depend on its temperature? (Draw a plot to support your answer.) Which of the following blackbodies produces the most IR radiation, a 10,000 K blackbody or a 3,000 K blackobdy. Which of the two previous blackbodies appears the reddest?

Hertzsprung-Russell Diagram

• What is the utility of making plots of large data sets? What do correlations in plots mean? What don't correlations in plots show?
• What is the Herzsprung-Russell Diagram (H-R)? Draw an H-R diagram and carefully label the various portions of the diagram.
• What information can we deduce about how stars evolve, the most common types of stars, ... from the HR diagram (directly and when coupled with other information, such as the blackbody laws)?
• What are Main Sequence Stars? Which phase of stellar evolution is the most long-lived? What types of stars are the most common, the brightest ones or the faintest ones? What types of stars are the most common, the most massive ones or the least massive ones. Where do you find the largest stars in the H-R diagram? The smallest stars?
• What is the Russell-Vogt theorem? State the Russell-Vogt theorem. What is the most important stellar parameter?
• What is the Mass-Luminosity Relation? How does the luminosity of a Main Sequence star depend on its mass?

For completeness, I include the properties of the Sun. I don't believe that I will reach this material (in lecture), but on the off-chance that I do, I summarize the initial parts of the section on the Sun. The actual material covered in class will determine what will appear on the exam.

• What is the Quiet Sun? What is the active Sun?
  • Describe the appearance of the Quiet Sun and list its properties.
  • What are sunspots? What are prominences? What are filaments? What is the period of the solar activity cycle? The period for the variation of the number of sunspots visible on the surface of the Sun? Describe how the x-ray emission from the Sun appears to an observer on the Earth. 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?
• What is the rotation period for the Sun? How does the rotation period depend on latitude on the Sun?

Theoretical ideas which concern the Sun:

• How does the Sun generate energy?
• What is matter?
• Why are neutrinos a more interesting probe of the current Sun than photons (electromagnetic radiation)?