1) The attempts by 17th century Astronomers to measure stellar parallax were critical to scientists at the time who were trying to determine whether Copernicus' Sun-centered solar system model accurately reflected reality.

a) (7 pts) State how parallax angles are related to distance (are they directly proportional to distance, inversely proportional to distance or independent of distance?). Next, use a simple diagram and a brief 1-2 sentence statement to explain why this relationship (or lack of relationship) exists.

b) (7 pts) Explain how attempted parallax observations were used to "refute" the Sun-centered theory. Why was the theory later accepted as correct?

2) An astronomer is attempting to measure the absolute properties of the star Deneb in the constellation Cygnus. However, she can only measure Deneb's spectrum when it is very low on the horizon due to her location in the Southern hemisphere of Earth.

a) (2 pts) The measured peak wavelength of Deneb will occur at a wavelength that is (shorter, longer, the same) compared to the true peak wavelength.

b) (3 pts) The measured temperature of Deneb, based on its peak wavelength, will be (hotter, cooler, the same) compared to its true temperature.

c) (9 pts) Explain your answer to (a). If the measured peak wavelength is different from the true peak, explain why. If not, explain why not.

3) The star Sirius in the constellation Canis Major has a surface temperature of about 10,000 K, much hotter than our Sun's temperature of 6,000 K. Sirius has a composition nearly identical to that of our Sun, but if you compare the strength of the Hydrogen lines between Sirius and our Sun, you would find that the Hydrogen absorption lines in the Sun are much weaker. Explain the most likely reason these two spectra are different.

4) There are two important boundaries within the Sun where the method of energy transport changes due to changes in the Sun.

a) (7 pts) Describe why energy transport in the Sun changes between the radiative zone and the convective zone.

b) (7 pts) Describe why energy transport in the Sun changes between the convective zone and the photosphere.

5) Most of what we know about the corona comes from observations of its spectrum during total solar eclipses when the photosphere of the Sun is obscured by the Earth's Moon.

a) (7 pts) What kind of spectrum do we see when we look at the corona during a solar eclipse? (absorption, emission, continuous) Explain your answer.

b) (7 pts) Explain how the observation of different kinds of ionization species in the corona is evidence that the temperature of the corona increases the further one looks from the Sun. As part of your answer, explain why ionization species are related to the temperature of the gas.

6) Below is an energy level diagram for an atom of some unknown element, X:

State below (yes or no) which of these energies can be absorbed by this atom of element X with the electron in level 2. No explanations needed.

		E = 2  ________________		E = 12  ________________

		E = 6  ________________		E = 16  ________________

		E = 10  ________________		E = 22  ________________

Also, state which of the absorbed photons has the shortest wavelength:

7) To find the mass of some stars, Astronomers exploit the properties of binary star systems. Suppose an edge-on binary system has a companion star whose velocity can be easily determined by examining its Doppler shift. Describe how this information, along with the distance from Earth to the system and the angular size of the system, can be used to determine the mass of the central star in the system.

8) The diagram below represents an observer on Earth viewing an edge-on binary star system. The central star of this system is at rest relative to the Earth. No explanations needed for this problem.

For each of the indicated positions of the companion star, circle the correct answer:

a) (3 pts) At A, companion's light will be (redshifted, blueshifted, unshifted)

b) (3 pts) At B, companion's light will be (redshifted, blueshifted, unshifted)

c) (2 pts) At C, companion's light will be (redshifted, blueshifted, unshifted)

d) (3 pts) If the central star's mass were doubled, how would your answer to (b) change? (more blueshift, less blueshift, no change, more redshift, less redshift).

e) (3 pts) If the central star's mass were doubled, how would your answer to (c) change? (more blueshift, less blueshift, no change, more redshift, less redshift)