AST309L-Scalo: REVIEW SHEET FOR 1st EXAMThis exam covers these main topics: Drake equation, theories for the formation of planets, the detection of extrasolarplanets, and considerations of habitability. This corresponds to the textbook readings in the course syllabus. Thereis also some material on what distinguishes science from non-science and pseudoscience—this is important becausemany people claim that astrobiology is “not really science.” However I will only ask a couple of questions aboutthis on the exam. Note: pp. 12-13 in Ch. 1 will not be covered on the exam. There were also outside readings, twochapters from a book by Koerner and LeVay, that you are responsible for reading; a few questions based on thismaterial will appear on the exam, and it will be helpful anyway in understanding the significance of disks and themethods of planet detection.In addition to the review questions given below (I included a large number), the review questions at theend of the textbook chapters are all good, as are the “Think About It…” exercises scattered through the text. Themore of these you think about and try to answer, the better you will do on the exam and the better you willunderstand the material, but I realize this depends on how much time you have to study, and how interested youare. I recommend that you start looking through these questions now, to get a feel for the level of familiarity andunderstanding you will need in order to do well on the exam. Sample multiple choice questions very similar tothose you’ll see on the exam are also given on this review sheet.A. Some review questions. Be sure you can give clear, and in some cases concise, answers. Some of these aresimilar to questions occurring on the exam, although they will be encountered in the form of multiple-choicequestions. There are also four “homework questions” that I have sent you via class email, whose answersyou should already have found.1.What are the factors that are important in estimating the number of communicating civilizations in ourGalaxy ("N" in the Drake equation)?2.In descriptive terms, how is N related to the distance to the nearest communicating civilization?3.If you lived on a planet orbiting some other star in our Galaxy, what would likely be thedistance, on average, to the nearest star?4.If you were to send a signal at the speed of light to a civilization all the way across our Galaxy,about how long would it take? (e.g. A century? A million years? A billion? You just need to be able togive a rough number like this.)5.On p. 276 of your text is shown a photo of Frank Drake's license plate that says "NEQLSL" meaningN=L.6.In order for N to be large enough so that communicating civilizations are nearby (say within 100 l.y.)what is required?7.What is the fundamental reason we think that planets are necessary for life?8.What are the main reasons for thinking that planets are common around other stars?9.What is the evidence for disks around young stars? How might this suggest that planets are forming orwill form there?10.Explain why "infrared excesses" in the spectrum of a star might be a sign that the starpossesses a disk. Why might an infrared excess NOT be a sign of a disk? What else could it be?11. The "proplyds" images by the Hubble Space Telescope in the visual part of the spectrum appear quite abit smaller than the probable disks imaged by the infrared satellite IRAS and subsequent infrared observations.Explain why this makes sense. (If you can answer this, you are in good shape for this part of the exam.)12. What physical processes are thought to be responsible for forming protostellar disks? For convertingdisk material into planets?13.Explain in some detail the standard theory for the origin of the planets in the solar system, What is thedifference between terrestrial and giant (Jovian) planets in this scenario? How does this theory depend crucially onthe lifetimes of protostellar disks?14.What do the peculiarities of the orbits and rotational directions of some of the outer planets and theirsatellites suggest about physical processes that occurred in the early solar system?15.List and describe various observational methods for searching for planets, including their advantagesand limitations. (The answer to this would be fairly lengthy.) Explain why it is so difficult observationally todirectly detect a planet orbiting another star.16. Which of the proposed methods for detecting invisible planets around nearby stars can best or only beused in cases where our line of sight to the star lies perpendicular to the plane of the planet's orbit (i.e. planet's orbitis in the plane of the sky)? How about the parallel case?17. What are “free-floating planets” and how might one be discovered?18. What is the current status of detections of extrasolar planets? Discuss the masses and orbitalcharacteristics. What are the selection effects that cause us not to be able to reach definitive conclusions about, say,the fraction of stars with planets? Why is it that the confirmed detection of extrasolar planets around a pulsar mightnot be very useful, or at least ambiguous, for answering the planet formation questions of most interest for ourcourse?19. List a few of the major proposed space missions (SIM, Kepler, TPF/Darwin) designed to detectextrasolar planets, and the techniques they will employ.20. What is the fundamental reason why Kepler will be able to detect smaller-mass planets than ground-based programs?21. Certain elements have recently been discovered in the atmosphere of an exoplanet. What elements?What property of this exoplanet system allows astronomers to see these elements? What do these observations tellus about the eolution of the exoplanet?22. Discuss several things that could “go wrong” in the evolution of a planetary system and notresult in the formation of planets at all, or a terrestrial-like planet, or a habitable planet.23. Discuss which spectral or other “biosignatures” are expected to be useful in searching for lifearound extrasolar terrestrial-like planets. (There are several of them.)24. Explain the concept of a liquid water habitable zone. What determines (a)its distance from the star, and (b) its inner and outer limits?25. Explain what might be the habitability problem(s) for planets orbiting starsmuch more massive than the sun, binary star systems, or extremely old stars. Whatabout “rogue” or “free-floating” planets? What
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