AST309L Fall 08-Scalo REVIEW SHEET FOR 1st EXAM The major topic for this exam is habitability, especially the “habitable zone,” even though we will have only taken two lectures for it. This material is covered in sections 10.1-10.4 and 11.1 in your textbook. We will not go further than sec. 11.1, and postpone sections on detection of exoplanets and their properties to the next exam. There is also assorted material in chapters 12, 1, 2, and 3 as detailed on a handout you should have already downloaded (under “Reading” at website). The rest of the material consists of parts of chapters 12 (Drake equation), 1, 2, and 3, as detailed in the reading list handout. See also below for a few topics not on the exam. The general problem that is being posed for this exam, and for most of the entire course is: If we think there is a chance that we might be able to detect signatures of life, or even intelligent life, on planets orbiting other stars, we will be using some sort of telescope, but how do we decide what stars we should “look” at? Out of thousands of stars of various types in the solar neighborhood, how can we narrow down the list? We will only have time to monitor about a hundred stars at most. If we detect planets that are even roughly like the mass of the Earth, how would we know which ones might be most likely to be “habitable” in terms of liquid water and other factors? That is the main focus, the arguments for thinking that life might be common, and reasons that could leave us pessimistic about any such search for extraterrestrial life. Examples of the latter are: If life depended on having a planet whose rotation was stabilized by a large moon like ours, or if the habitable zone in our solar system, as controlled by climate effects, only extended from 0.95AU to 1.05AU (if you don’t understand why this would make habitable planets unlikely, you should begin studying now!). So part of your task is to understand why there are these inner and outer limits to the habitable zone, how they depend on a planet’s properties, how the HZ probably varies with time in our solar system, and why the HZ will be at other distances from different types of stars. There are four pdfs of lecture slides at the web site. We covered all of the Sept. 2 and Sept. 4 sets of slides, except for the last few slides on Kepler’s and Newton’s laws. I decided not to include any material on Kepler and Newton on the exam. Also remember that I will not test you on the material about the nature of science or what gravity “really” is, even though these are interesting topics. The first part of that slide set was discussed in detail (concerning the elements probably essential for life as we can imagine it), and has several points not covered in your textbook, so be sure to review them. We did not cover the slides for Sept. 9 in class—these are on light, and on using spectral lines to learn that moderately complex organic molecules are not as uncommon as we might have guessed. Look them over yourself—it is mostly review except for the examples of molecular line spectra from star-forming clouds. There isn’t anything specific to memorize here. THERE IS ALSO AN ASSIGNMENT at the bottom of the fourth-from-last slide. I’ll repeat it here, since I am likely to ask you about it on the exam: Assignment 1: Have any amino acids been detected in space? Begin by trying Wiki with “glycine”. Is this up to date? Has glycine been discovered in space yet? Have any other amino acids been found? (Not “components of amino acids” or “upper limits”, which means a non-detection, but a positive detection of an amino acid.) You don’t have to know its name, but is it an amino acid used by life on Earth? Where was it detected? You will have to go further than Wiki to find the answer. Hint—the discovery was made this year. Slides from 9/11 and 9/16: This single long pdf file has 36 slides, but ignore 34-36 (I meant to extract them). It covers the major topic of the exam, “Habitable Planets,” chapters 10.1-10.4, and 11.1. The ways in which distance from star, star’s luminosity, and especially climate effects, determine a planet’s temperature are especially important, so don’t forget to take advantage of the Tutorial at the textbook web site on “Surface temperature of terrestrial planets.” There is also a second “Assignment” near the end of that file, which I’ll copy here—it is likely I will ask you about it on the exam. It is related to material near the end of the slides on the types of stars we should search for habitable planets. Assignment 2: In March 2007 astronomers were surprised to discover that protoplanetary disks exist around binary star systems. Using the “Links” in your textbook web site, find out what telescope was used to make this discovery. What is it about this telescope that makes it perfect for detecting disks? You will find the background material for this question in the “Links” for “”Stars and Habitable Planets” at the textbook web site.It is convenient to divide up the questions on the exam into the following areas, remembering that there will only be about 3-5 questions for most of them, but more for habitable planets and star systems. A. “Galactic neighborhood,” having to do mostly with distances, to the nearest stars, across our Galaxy, etc. (all in light years); you should also know the age of the Sun, the age of the Galaxy, and (very roughly) the number of stars in the Galaxy. B. Drake equation. Remember you don’t have to “solve” the equation, just be familiar with how the number of stars having planets, or planets with life, or with intelligent life, consists of a series of probabilities which, when multiplied together, can give an extremely small number. Also understand why the duration of life on a planet, or of a communicating civilization, is so crucial to what is implied by the equation. C. “General background” – this is a catch-all for your reading in chapters 1, 2, 3, and covers the main questions of astrobiology as in ch.1 of your textbook, how common or uncommon the basic building blocks for life are (elements and molecules—we covered this in detail in class: see lecture pdf), Kepler’s and Newton’s laws are not on the exam, but basics about light are (only 2-3 questions). These are in a lecture pdf that I did not cover in class, but are also in
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