Introduction to Astronomy

Spring 2015

This picture from Astronomical Picture of the Day, shows the protoplanetary disk of gas and dust that surrounds the star HL Tauri. It was imaged at millimeter radio wavelengths of light by the new Atacama Large Millimeter Array in Chile. This is one of the most important images in astronomy in the last few years, because it helps us to understand how planets form. The system is only about a million years old, and the central star - not shown at this wavelength and now growing only very slowly -- is still surrounded by a dense disk of gas and dust. Radial gaps in the disk show up as dark ellipses; our understanding is that these are created by planets that grow in the gaps by swallowing up nearby material. So at least about half-a-dozen planets appear to be forming in this system. The disk is about 90 AU in radius; this is about twice the radius of Pluto's orbit in our Solar System. HL Tauri is about 450 light years from Earth in the disk our our Milky Way galaxy. We will talk about the lives of stars in the second section of the course and about planets and planet formation in the fourth section. This image will be featured in the lecture of Tuesday, April 7th.

Final Update

Final grades were submitted to UT at 3:05 PM on Monday, May 11, 2015.

The course is now finished and no further changes to the grades will be made. Grades are lower this year than they have been for the past few years. This had to happen at some point: almost every class that I had for several years now was the best class that I ever had. This cannot go on forever. I am sorry that the lower grades came this year, but every class cannot be above average.

We lost one test because of bad weather. This is not the reason for the lower grades. I emphasized many times that I provide two score "drops" so that, if you lose one or even two grades because of some unforeseen circumstance, you still have enough scores for a final grade. Bad weather was an unforeeseen circumstance like any other; the only difference was that it affected everybody. But that's exactly why we had the flexibility of two score drops. In fact, I provided 2 score drops only a few times in the 25 years that I have taught this course, and all the classes that had only one score drop did OK, including this one.

Every class develops its own culture, and this year's class culture had some problems. I want to emphasize: some of the best students that I have ever had were in this year's class. Also, many people consistently tried very hard to do well. So these remarks emphatically do not apply to everybody. But in general, this class was less "engaged" than previous ones -- fewer people attended lectures, and fewer people talked to me about their problems. I do not know all the reasons, but two possible reasons are concerns. First, I posted two complete copies of each lecture -- not just the powerpoint slides, but the complete audio from the 2014 classes. This may have caused some students to decide that they could skip classes. This is never a good idea. Second, a class culture on Facebook seems to get more important every year. I cannot prevent this; your right to free speech guarantees that you can operate a Facebook page. I could imagine that Facebook can be helpful. But in practice, there are too many ways that it can undermine the teaching process. I have to take both circumstances into account in future years. Anyway, this class was slightly less engaged, so the grades are slightly less high.

But I emphasize: The grades are nevertheless quite good. The median grade is a B-. Only 36 percent of the class got C-, C, or C+. Only 7 percent got Ds, and only 3 people failed. This is still substantially better than the University expects when it describes C as "average" and B as "above average". But 56 percent of the class got either a B or an A. So, on the whole, you did well. I appreciate the effort that you put into the course; I know that it is not easy for all of you. This is a University course at a highly ranked university. The standards are correspondingly high. I hope that this course has been an important part of your educational experience.

The true grade distribution is better than the above table suggests. The reason is that some people took the course on a CR/noCR basis, and they should not be included in the letter grade distributions. These people usually have relatively low numerical scores, because they don't need high scores to get a CR. I don't know who took the course for CR until I submit final grades. So these people are included above, and they bias the score distribution toward lower grades.

After removing CR scores, the final number of people with C+, C, C- is 15, 30, 10. The number of people with D+, D, D- is 6, 2, 1. So the percent of people who got letter grades of A, B, C, and D is 19 %, 42 %, 33 %, and 5 %. This is better than before CR scores are taken into account.

I wish all of you every success in everything that you do. It has been a pleasure to have you in my class.

John Kormendy

Unique number: Sections 47320
Classes: Tuesday and Thursday at 12:30 - 2 PM in Welch 3.502
Instructor: John Kormendy 
Office: RLM 15.326
Office Hours: Tuesday and Thursday from 2:00 to 3:20 PM in RLM 15.326
Office Telephone: 512 - 471 - 8191 (Please don't leave phone messages; send email instead.)
Teaching Assistant: Myoungwon Jeon (Grade Recorder)
Office: RLM 16.216
Office Hours: Monday at 2 to 3:30 PM
Telephone: 512 - 471 - 0445
Teaching Assistant: Ankith Shanthiraj
Office Hours: RLM 17.307
Office Hours: Wednesday at 3 PM to 4:50 PM
Telephone: 512 - 905 - 4817

Spring 2015 syllabus as a jpeg file or as a pdf file

Schedule of help sessions in 2015:

TA's Help Session for Homework 1: Wednesday, February 4, 2015 from 5 to 6:30 PM in Welch 3.502

TA's Help Session for Homework 2: Monday, March 2, 2015 from 5 to 6:30 PM in Welch 1.308

TA's Help Session for Homework 3: Monday, April 6, 2015 from 5 to 6:30 PM in RLM 4.102

John Kormendy's Help Session for Exam 1: Monday, February 9, 2015 from 5 - 6:30 PM in WCH 1.120

John Kormendy's Help Session for Exam 2: Wednesday, March 4, 2015 from 5 - 6:30 PM in Welch 3.502

John Kormendy's Help Session for Exam 3: Monday, March 9, 2015 from 5 - 6:30 PM in RLM 4.102

John Kormendy's Help Session for Exam 5: Wednesday, April 8, 2015 from 5 - 6:30 PM in WCH 1.120

John Kormendyy's Help Session for Exam 6: Wednesday, May 6, 2015 from 5 - 6:30 PM in ETC 2.108

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 illustrating the Doppler effect for sound. Light behaves similarly, but "lower pitch" corresponds to a color shift toward the red. Watch the light on top of the police car change color as the pitch of the sound changes. Of course, in reality, the blueshift (at the beginning) and the redshift (at the end) would be extremely tiny at the speed of a police car.

Applet illustrating observations of binary stars

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 the Opportunity rover on Mars

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!

Dates in the following text are updated for Spring 2015.


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, 12th, or 13th 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 13th Edition and may not correspond to those in earlier editions. Important: Buying the text is optional. Most people find it helpful to have a textbook in which they can read another author's description of the things that we talk about in class. However, (1) all class slides will be posted on this class web site, and (2) all 2014 lectures were recorded and are posted on this class web site. So you can listen to any lecture more than once. Therefore, you can get through this course without having a textbook if you study and understand the material that I cover in class.


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 post the lecture slides well in advance. Don't let the convenience of posted slides and lectures fool you into thinking that you can skip class. The in-class lectures are an important part of the education experience. If you skip classes and study only from the postings, chances are that you will pass the course but that your grade will be lower than it could have been. This is not because I am nasty to people who skip classes (I'm not) but rather because you will not know the material as well.


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 homework due dates.


even if I am out of town. Astronomy is an observational science. My research depends in part on visits to various observatories, including the University's McDonald Observatory in west Texas. Also, occasionally, I have to attend an out-of-town meeting. If I miss a class for these or any other reasons, the class will meet as usual.


You may be interested in the Astronomy Department's regular evening star parties, when you can see some of the objects that we discuss in class through one of our telescopes. They happen on Wednesday nights on the roof of RLM and on Fridays and Saturdays at Painter hall. Please see this link for details..


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.


There will be 6 in-class exams (see the syllabus). Four of these will follow and cover the 4 major sections of the course. The fifth and sixth essentially are makeup exams that follows Section 2. So the first half of the class will end with 3 exams on successive class days ending at the start of Spring Break. If you take all 6 exams and do all the homework, you will have 7 scores, each worth 20 % of your final grade. We will then drop your lowest 2 scores and average the rest. There will be no final exam. There is no penalty for missing any one exam or the homework as long as you get 5 total grades (either 4 exams and the homework or 5 exams and no homework). For this reason, there will be no makeup exams, not even for valid reasons such as medical or family emergencies.


I emphasize again: THERE WILL BE NO MAKEUP EXAMS, EVEN FOR VALID (E.G., MEDICAL) REASONS. Please don't ask. I will be polite, but the answer will have to be "no".


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 me 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. Homework is optional (see below).

Here's another description of how we will get your final grade: You can get 7 scores, each of which counts 20 percent of your grade, for 6 exams and all four homeworks averaged together. We will then drop your lowest 2 scores and add up the other 5. This means that you can decide not to do the homework and still be OK if you take all the exams. But if you miscalculate and have to miss two exams AND you decided not to do the homework, then I cannot help you to make up a fifth score by giving you a makeup exam or other extra credit work. So think carefully before you decide not to do the homework.

If you decide to do the homework, please make sure that you do all 4 homework assignments.

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.

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!

If we see evidence for copying, such as two detailed but identical answers, then both students will get zero for that question. In cases of widespread copying, both students will get zero for the whole homework and may get reported to Student Judicial Services.

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. Important: If you get the correct answer but show none or almost none of the steps that you went through to get the answer -- in other words, if we cannot tell that you did the work to get the answer -- we will give you only 50 % of the full marks.


Laptops can be used in class to keep up with the slides that I show. All slides will be posted well in advance of the lectures. If you want to make notes using your laptop, this is OK. Alternatively, you may want to print out the slides in advance and take notes on the printouts. Either way, you will find that you need to take some notes but not a lot of notes.

During classes, please do not use laptops for web browsing that is not related to the course.

Cell phone use is not allowed, please. NO TEXTING DURING CLASSES.


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 2014 - Spring 2015.

 1. Adds/Drops before the 12th class day: During the first four class days, students may add or drop courses online. The 2015 Spring 4th class day is January 23. 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 2015 Spring add/drop day (12th class day) is February 4.

 2. Dropping a course during the open Q-drop period: The 2015 Q drop period ends on April 6. 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. Again, the 2015 Spring Q-drop deadline is April 6.

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 6, 2015.

 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

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