Introduction to Astronomy

Spring 2012

A supernova (the bright star at lower-left) exploding in the galaxy NGC 4526, which is a member of the Virgo Cluster of galaxies, at a distance of about 55 million light years. This 1994 image from the Hubble Space Telescope shows mainly the galaxy's inner disk of dark dust embedded in the glow of billions of stars in the outer parts of the galaxy. A larger-scale view (rotated by roughly 180 degrees) of the outer part of the galaxy is shown here. Supernovae of "type Ia" such as this one are one way that stars die (Section 2 of this course). They have become especially important in the past 10-15 years because they are bright enough to be seen very far away and standard enough in their maximum brightnesses so that astronomers can measure their distances accurately. Studies of many distant supernovae have led to the astonishing discovery by two independent teams that the well known expansion of the Universe is speeding up. The cause of this acceleration is believed to be a "dark energy" that makes up 72.5 percent of the mass-energy density in the Universe. Dark energy is not understood, but we already know that deciphering it will affect the most fundamental foundations of physics. Many observing campaigns are planned or under way to study dark energy in more detail. This subject is covered in Section 4 of the course.

"For the discovery of the accelerating expansion of the Universe through observations of distant supernovae", the 2011 Nobel Prize in Physics was awarded to team leaders Saul Perlmutter, Brian Schmidt, and Adam Riess.


Final grades for both sections were posted on Friday, April 4, 2012. The course is now finished and no further changes to the grades will be made. The final conversion to letter grades was made using the table (still included below) that I announced at the beginning of the course.

I am delighted by how well you did. The grades are very high. More than any other class that I have ever had, you were interested and engaged. You tried hard to do well. As I promised, this has paid off. Also as I promised, I never reward hard work by making the grade curve harder. As a result, your distribution of grades is skewed to As and Bs by much more than the University expects. I am very happy about this. You should be proud of yourselves, as I am proud of you.

This is the distribution of grades:

97 A

50 A-

53 B+

42 B

40 B-

36 C+

22 C

17 C-

8 D+

3 D

0 D-

9 F

7 CR

You were the best class that I have ever had. And you made it a pleasure to teach the course.

Warmest best wishes to you all for successful and happy careers and lives, John Kormendy.

Unique number: Sections 47605 and 47615
Classes: TuTh 12:30 - 2 PM and 2 - 3:30 PM in Welch 3.502
Instructor: John Kormendy 
Office: RLM 15.326
Office Hours: Wednesday from 4 to 5:30 PM in RLM 15.326
Office Telephone: 471-8191 (Please don't leave phone messages; send email instead.)
Teaching Assistant: Rodolfo Santana
Office: RLM 16.318
Office Hours: Monday from 11 AM to 12:30 PM in RLM 16.318
Office Hours: Monday from 5 to 6:30 PM in RLM 16.318
Telephone: 471 - 3466
Teaching Assistant: Emma Yu
Office: RLM 15.310F
Office Hours: Monday from 1 to 2:30 PM in RLM 15.310F
Office Hours: Friday from 3:30 to 5 PM in RLM 15.310F
Telephone: 471 - 3647
Teaching Assistant: Michael Eskew
Office: RLM 15.203
Office Hours: Wednesday from 11:30 AM to 1 PM in RLM 15.203
Office Hours: Friday from 12 noon to 1:30 PM in RLM 15.203
Telephone: 232 - 3958
Teaching Assistant: Carlos Oliveira
Office: SZB 340
Office Hours: By appointment in SZB 340 (in the back of the room)
Telephone: (512) 772 - 4408

Spring 2012 Syllabus.

Powers of Ten Tutorial

This is a Java tutorial that gives you some feeling for the scales of things (both large and small) that we will discuss.

Time zone map

There are small inconsistencies between the above map and the one that I show in class, e. g., in Australia, where the posted map does not show three, half-hour time zones meeting at one place. Countries frequently make changes in their time zones; the posted map (from 1997) is slightly out of date. During the 2000 Millennium celebration, the time zones were as I show them in class.

Applet demo of the retrograde motion of Mars

Applet illustrating the Doppler effect

Movie of how the Moon's phase, size, and apparent Earthside face change over a month. I show a movie similar to this in Lecture 2.

Astronomical Picture of the Day

Mars: A selection of Mars Global Surveyor images

Mars: Evidence for recent liquid water

Mars: NASA homepage for Spirit and Opportunity rovers on the surface

Annular eclipse of the Sun by Mars's moon Phobos as seen from the surface of Mars by the Mars Exploration Rover Opportunity

The Inner Solar System Now!


This course is an introduction to astronomy for non-science majors. We start with explanations of the seasons on Earth and of what you see when you look up at the sky. Two lectures cover the history of astronomy from the ancient Greeks until the Renaissance. The history of astronomy is also the history of the development of the way that we do science; we will see why science is so successful in teaching us new things. Throughout the course, I try to show you how we learn things about our Universe. I then discuss stars - their formation, life histories, and deaths. This section includes a discussion of our Sun. From stars, we expand our horizons to the study of galaxies of stars and of the Universe as a whole. We look back in time to the beginning of the Universe to give us perspective on how everything around us was created - everything from the stuff that you and I are made of all the way out to the most distant stars. Given this perspective, we then return home to our Solar System. I describe the planets, moons, comets, and asteroids, and I put our planets into context by comparing them to the planets that astronomers are now finding around other stars. All this leads up to a discussion of our Earth, of the history of life on Earth, and of the prospects that there is life elsewhere in the Universe. The emphasis throughout the course will be on conceptual understanding of the "big picture". You will be astonished by how much we can learn about places far away and long ago.


It helps if you had high school science courses, but I do not expect this or require it. I will - as much as possible - start each subject from the beginning. There is only a little math in the course, and even people who have "math anxiety" usually find that the math is not a big problem. I will use "scientific notation" for large and small numbers, and I will introduce about half-a-dozen equations that describe how nature behaves. You never need to memorize equations. If you need them on exams, I will give them to you. But you need to understand what they mean and how to use them. Here is a question that is typical of the reasoning that you may be asked to apply: Your SUV has a 20 gallon tank for gasoline, and you can drive 24 miles with one gallon of gas. If you want to drive 1000 miles, how many times will you have to fill the tank? Most of the mathematical reasoning involves ratios and proportions, and all of the arithmetic that I ask you to do during exams can be done without a calculator.


Horizons: Exploring the Universe by Michael Seeds and Dana Backman, published by Brooks/Cole and available at the Co-Op. You can get the 9th, 10th, 11th or 12th Editions. Older editions are not bad. If you get one, then you will have to be careful about reading assignments: the pages and section numbers mentioned in assignments will correspond to the 12th Edition and may not correspond to those in earlier editions.


VERY IMPORTANT: I strongly recommend that you attend classes. Astronomy is not intrinsically difficult, but it is probably unfamiliar to you, and it is much harder to understand the material if you only read about it. Also, I will omit some subjects that are in the book, and I will lecture on other subjects that are not in the book. You will be responsible for the content of the lectures. I will distribute handouts on the most important things that are not in the book. Don't let the convenience of handouts fool you into thinking that you can skip class. The handouts are supposed to help you to remember what I said. They are not a substitute for coming to class. If you skip classes and study only from the handouts, chances are that you will pass the course but that your grade will be lower than it could have been (for example, C or D instead of B). This is not because I am nasty to people who skip classes (I'm not) but because you will not know the material.


There will be 5 in-class exams (see the syllabus). Four of these will follow and cover the 4 major sections of the course. The fifth is essentially a makeup exam following Section 2. Your lowest exam score will be dropped and the average of your other exam scores will make up 80 % of your final grade. The remaining 20 % will be the average grade on the 4 homework assignments. There will be no final exam. There is no penalty for missing any one exam as long as you take 4 of the 5 exams. For this reason, there will be no makeup exams, not even for valid reasons such as medical or family emergencies.


If you have trouble understanding something in the course, please ask questions in class or come and see me. I will be happy to discuss the problem with you. The TAs are also available. Review sessions will be scheduled prior to exams and otherwise as needed.


Astronomy is an observational science. My research depends in part on visits to various observatories, including the University's McDonald Observatory in west Texas. If I miss a class for this or any other reason, the class will meet as usual.

You may be interested to visit our Student Observatory on the roof of Painter Hall. It houses a 9 inch refracting telescope. For information on viewing times, please consult our Educational Services Office.


The University of Texas at Austin provides upon request appropriate academic accommodations for qualified students with disabilities. For more information, contact the Office of the Dean of Students at 471-6259, 471-4641 TTY. Also, please notify me of any modification/adaptation that you may require to accommodate a disability-related need. Specialized services are available on campus through Services for Students with Disabilities.


Homework assignments will have a due date that is 2 weeks from when the homework is distributed. Late homework will not be accepted unless you have given and I have accepted your reason for requesting an extension prior to the due date. No homework will be accepted after I have discussed the answers in the help session that preceeds each exam.

Exam dates: The syllabus lists the dates of the exams. I promise not to change these dates. Please note the dates of the exams, since it is impractical to schedule makeups. Substituting exam 3 for one of the other exams gives you flexibility in case you have to miss a test.

I emphasize again: There will be no makeup exams.

There will be no final exam.

Copying during exams is a crime for which the punishment will be at least an F for that exam and very possibly an F for the course. I will not hesitate to report cheating to the Dean of Students. University standards of academic integrity are posted here.

All work handed in for grading must be your own work. It is OK to discuss homework with a friend, but it is important to use your own thoughts and words in writing your answers. If you are puzzled by a question, do not copy a friend's answer. Instead, please discuss the problem with me or with a TA. Don't be shy! We are here to help!

Recommendation: When you write homework solutions, show intermediate steps; don't just write down the answer. When the TA grades the homework, he or she needs to see how you thought about the problem. If you get the wrong answer but thought about at least some of the problem correctly, you get partial marks. If the intermediate steps are not shown and the answer is wrong, we can't give you any partial marks.


Cell phones and laptops:Use of laptops is strongly discouraged. They get in the way of understanding, and they cause distraction for other students. The best way to take notes is NOT to use your laptop but rather to write on the class handouts. You will find that you don't need to do a lot of writing.

Cell phone use is not allowed, please. NO TEXTING IN CLASS.


Information on astronomy courses and on Departmental rules are posted in the Astronomy Department's Memo to Undergraduate Astronomy Students Copies are handed out on the first day of classes.


The University's deadlines and rules regarding dropping the course will be strictly enforced. I will assume that you know the deadlines and the rules. Deadlines are listed in the University's Calendar for Fall 2011 - Spring 2012.

 1. Adds/Drops before the 12th class day: During the first four class days, students may add or drop courses online. The 2012 Spring 4th class day is January 20. During days five through twelve, students may drop a course online but must go to the department offering the course to seek permission to add a course. Be advised that some departments do not allow adds/drops after the fourth class day. Students who wish to add a class after the twelfth class day will be required to see a counselor in the Student Division of the Dean's Office and provide justification for the proposed change. The 2012 Spring add/drop day (12th class day) is February 1.

 2. Dropping a course during the open Q-drop period: The Q drop period is from February 2 to April 2. A student who wants to drop a course can ask the instructor to complete a drop form that assigns a Q or an F. The symbol Q indicates an average of C or better at the time of the drop, or that no grade has yet been assigned, or that due to the student's performance and the nature of the course, no academic penalty is in order, or that for documented non-academic reasons, no academic penalty is in order. The 2010 Spring Q-drop deadline is April 2.

I never refuse a request to Q-drop this course.

 3. The deadline for dropping a course or for changing to credit/no credit or for withdrawing from the University for urgent nonacademic reasons is April 2, 2012. Prior to the deadline but after February 13th, dropping or withdrawing requires a written appeal to the Student Division of the respective Dean's Office.

 4. Courses taken on a pass/fail basis:  The University defines a D- as a passing grade for undergraduate students. The instructor is obliged to assign a grade of CR (Credit) for a student registered on a pass/fail basis who has a D- or better in the course. It is important that the roster indicate the student is registered for the course on a pass/fail basis. Otherwise, a letter grade must be assigned. There is a time limit for students to change courses from a grade basis to pass/fail basis and vice versa. It is the same as the final deadline for drop/withdrawal for academic reasons. After that deadline, students should see a Counselor in the Student Division of the Dean's Office. Students are allowed to change the status of any given course only one time during the pass/fail time period.

John Kormendy's Home Page

University of Texas Astronomy Home Page

Final update: Friday, April 4, 2012. Total visits since Wednesday, January 5, 2012 =

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