Astronomy 101
Exam Essay Questions
4/6/2015
Greetings exam takers! Below is the set of 12 “big questions” that may appear on the Midterm and Final
Exams in ASTR101 this quarter. You will only write full responses for two of these questions on either of
those exams, but those two will be chosen at random just before the exam – so you must come prepared to
answer any two of the relevant questions (1-6 for the Midterm, 7-12 for the Final). Each is readily
discussed at a “science-lite” level within a paragraph or two, but the industrious students of this class are
advised to be as complete and thorough as possible, particularly in presenting evidence and physical
examples. An exhaustive answer to these questions might take volumes – however, you are encouraged to
keep it to less than three standard pages (4-6 pages in a typical blue book) per question. You should draw
your arguments and evidence from the text, from your lecture notes, and where appropriate from outside
readings and personal knowledge.
I am available to address your comments, questions, or concerns on these questions up until 8am on the day
of either exam (although I will guarantee written responses only to questions received prior to noon the day
before the exams). I strongly suggest that you take advantage of this opportunity to practice for these tests,
and encourage you to prepare meaningful and detailed answers for each question well in advance – and to
review those outlines with me. Your preparation will pay off with a much easier and more successful
experience!
1. We have learned in this class that even while sitting perfectly still in the deepest meditation, each of us is
hurtling across the universe at speeds that are, frankly, astronomical (How far did you move while
reading that sentence? Over 100,000 kilometers!). Beginning at the level of the rotation of the Earth,
describe in detail the various motions in which humans participate and the structures through which they
move, up through the movements of galaxies within groups and clusters. What does this constant state of
motion imply about the apparently separate nature of your movements through 'space' and 'time'? How
has the difficulty of perceiving these motions affected our understanding of astronomy through history?
(See Chapters 1-3, Lectures 1-3.)
2. While there are many aspects of the night sky which change regularly, the rapidly changing Moon is
amongst the most noticeable and significant. Fortunately, it is also amongst the most straightforward to
observe and to understand. As clearly as you can, describe and explain using physical examples both (a)
the cycle of lunar phases, and (b) total and partial eclipses of the Sun and Moon, all as viewed from the
Earth. You may find it helpful to use sketches to make your points clear, but note that any figures you
wish me to consider must be well labeled! (See Chapter 2, Lectures 2-3.)
3. Evidence from early human civilizations suggests that from its very beginnings, mankind has made
careful observations of the sky and attempted to predict and explain the patterns of motion and location
seen there – particularly those of the Sun and planets. Briefly trace the history of attempts to predict the
movement of the planets, from human pre-history to the revolutionary developments of Copernicus,
Galileo, Kepler, and Newton. Why were these issues so important so early on? What key technologies
and ideas played a part in bringing the true nature of the Solar System to light? (See Chapters 2-4,
Lectures 2-4.)
4. No general astronomy class could be complete without discussing how the Sun, the Earth and the other
planets form and came to be in the arrangement that we observe today in our Solar System. Present,
explain, and justify the currently accepted model of the formation of the Sun and Solar System (in
particular), as well as other stars and planetary systems in general. How does that model address the
patterns of physical evidence in the Solar System? What new insights have we gained from looking at
other stars and their planetary systems? (See Chapters 6-10, Lectures 5-7.)
5. Astronomy has always been driven by observations of the heavens, and the telescope has been at the
vanguard of this work, from Galileo’s sketches of the moons of Jupiter, to modern views of distant
galaxies from the Hubble Space Telescope. At a physical level, why is it generally the case that “bigger
is better” is the rule in the construction of telescopes? Is it always so? Address these questions and state
the scientific, engineering, and economic cases for and against large telescope construction. What
advantages do space-based telescopes uniquely provide? What limitations do they suffer? (See Chapter
5; Lecture 8.)
6. Our star is frequently referred to in the popular scientific press as an ‘average’ star, or ‘typical’ of most
of the stars in our galaxy. To what degree is this sentiment actually true? Compare and contrast the
important physical characteristics of the Sun with the most common types of stars in our galactic
environment. In what ways is the Sun in fact similar to the most common types of stars in the Milky
Way? In what ways does the Sun stand out as unusual? (See Chapter 11-13, Lectures 9,10)
7. The “death throes” of stars are amongst the most complex phenomena in all of astronomy, and the
“corpses” of stars amongst the most energetic and exotic objects in existence. Beginning at the end of the
core helium fusion stage in a star’s life, describe in detail the post-main sequence development of both
(a) a 1.0 solar mass star, and (b) a 25.0 solar mass star. In what significant ways do they differ? What role
does each of these types of stars play in the “star-gas-star” cycle and the evolution of chemical elements
in our galaxy? (See Chapters 12, 13; Lectures 10-14.)
8. Throughout human history, the glow of the Milky Way stretching across the heavens has been an
inspiring sight, and thanks to hundreds of years of research, we now have a very detailed picture of the
shape and content of our galaxy. Discuss the physical characteristics of the Milky Way and its major
components, including a detailed sketch of the major structures and indications of their sizes. Be sure to
write about not only the stars in our galaxy, but also the gas, dust, and dark matter that shape our own
galactic home. (See Chapters 15, 18; Lectures 14, 16-17.)
9. Star Wars, Serenity, and Santa Conquers the Martians – since an awareness of the true nature of planets
and stars was first achieved, humankind has been fascinated with the possibility of finding life on other
worlds. Based on your understanding of the properties a planet must possess in order to sustain life,
discuss the ongoing search for and likelihood of finding not only simple life, but also other advanced
civilizations on worlds orbiting other stars within our galaxy, and the wider universe. What role do key
paradigms such as Drake’s Equation and Fermi’s Paradox play in this debate? (See Chapter 19; Lecture
15.)
10. In the early 1920’s, astronomers such as Edwin Hubble revealed that our galaxy was not alone in the
universe, and that in fact there are likely as many galaxies in the universe as there are stars in our own
galaxy. Since then, studies such as1995’s Hubble Deep Field project have revealed even more details of
the diversity of galaxies in our universe, providing astronomers with insight as to how the galaxies that
we see have come to exist. How do we believe that galaxies form and evolve? What evidence do we have
supporting these models? Discuss the characteristics of the three major types of galaxies, how they are
observed, and what those observations tell us about the “life story” of galaxies. (See Chapters 16-18;
Lectures 16-19.)
11. Over the past 30 years we have discovered that the majority of matter and energy in our universe is in
some form that we do not fully understand – so-called “Dark Matter” and “Dark Energy”. Describe in
detail the evidence that leads us to believe that Dark Matter exists, and the two broad categories of
possible forms that this Dark Matter might take. Similarly, describe the evidence suggesting the existence
of Dark Energy, and the effect it appears to have on the observed expansion of spacetime. What do each
of these mysterious ideas suggest about the future of our universe itself? (See Chapters 16-18; Lectures
16-19.)
12. Despite its sometimes mind-boggling implications, the ‘Big Bang Theory’ has made a home for itself
amongst the most successful scientific models ever created. It ties the most distant observable features in
the Universe to the creation and distribution of atomic building blocks of matter, makes testable
predictions that have been repeatedly and exhaustively verified by experiments, and provides clues to
events in the most unimaginably distant past and future. Describe in detail the basics of the Big Bang
model, the evidence in favor of it, and what the early history of the universe was like. (See Chapters 17,
18; Lectures 17-19.)