Answer any 12 of the following 14 questions. All relevant equations have been given on the cover page (not visible in WWW version). Each is worth 8 points.
2) Name and explain two different pieces of evidence that tell Astronomers the solar corona's temperature increases as one looks further away from the Sun. I am not asking for an explanation of the mechanism behind this heating (equipartition of energy argument) but rather the actual observations that prove the temperature gets hotter further out. Name each piece of evidence and explain why it relates to the temperature.
3) Why is energy transported outward in the Sun via light in the radiative zone? Also, why is energy transported outward via convection in the convective zone?
4) Astronomers make careful observations of star Gamma and star Delta to determine their properties. Both stars are determined to have the same spectral line widths in their continuous spectrum, but Star Gamma's continuous spectrum peaks at a much shorter wavelength than star Delta.
5) Suppose our galaxy had no dark matter. What would the rotation curve for the disk of the galaxy look like? Draw in what you think it would look like on the graph below. The Keplerian curve (which we see in our solar system) is included for reference. If the galaxy¹s rotation curve would exactly match this, just write "no change" on the graph below. After drawing in your curve, explain why you drew it the way you did (or wrote "no change").
6) During star formation, a cold, dense cloud of gas and dust slowly shrinks. Eventually, nuclear fusion ignites in the center and a star is formed. During that shrinking process, but before the onset of nuclear fusion, state in one word (increasing, decreasing, unchanging) and explain (one sentence why for each one) what is happening to the self-gravity, the density, the temperature and the outward-pushing pressure of the cloud.
7) A recent search for brown dwarfs observed binary systems in which one of the stars was similar to the Sun. Astronomers hoped to use the motion of the sun-like star to reveal the presence of a brown dwarf companion, but it turns out this wasn¹t a representative sample of binary systems. It was biased against finding brown dwarfs. Explain why.
8) Suppose you observe the spectrum of a binary star system (the system is so far away that the light from the two stars blends together, it is an "unresolved binary" system). The spectral lines from the system split and merge, split and merge, etc. over time. Assuming we are observing this system edge-on, explain what you would measure and how you would use your measurements in order to determine the central mass of this binary system.
9) Two Cepheid variable stars, Alpha and Beta, have the same average apparent luminosity, but Alpha has a pulsation period that is twice as long as Beta. Assuming no interstellar extinction/reddening corrections are necessary, which star is further away? Explain fully how you determine your answer.
10) Explain why Helium fusion requires a higher density and temperature compared to Hydrogen fusion, then explain how and why the onset of Helium fusion in low mass stars sometimes leads to a planetary nebula.
11) Explain how we think elliptical galaxies form differently from spiral galaxies. How does this formation process account for the lack of gas and dust in ellipticals? How does it account for the red color of ellipticals (as opposed to the blue color of spirals)?
12) If we estimate the distance to a spiral galaxy using the Tully-Fisher (TF) method, we will get an incorrect answer if we do not account for the inclination of the galaxy with respect to our line of sight. Will we underestimate or overestimate the distance to the galaxy in question if we fail to correct for inclination? Explain your answer.
13) Suppose we measure the abundance of Carbon in the spectra of galaxies at a variety of distances from the Earth. Some of the galaxies in our sample are billions of light years away, and some are relatively close. On the graph below, sketch the trend of how you think the observed Carbon abundance would vary with distance (would it be constant, increasing or decreasing?), then explain why you drew the graph the way you did.
14) An important aspect of current SETI research is planned NASA missions to Mars and Europa to find out if life has ever existed (or currently exists) in any form on either of these two worlds. If we do discover traces of life (just the simplest microorganisms, nothing intelligent or civilized), explain how and why this will affect our estimate of "N", the number of intelligent communicative civilizations in the galaxy.