ASTR 220 Collisions in Space

Spring 2005


ASTR 220 Collisions in Space is a 3-credit CORE Physical Science course. It does not have a laboratory section. There are no pre-requisites for this class.

As its name suggests, this course focuses on the many different types of collisions that occur as part of astronomical phenomena, from impacts between solar system bodies to binary stars to merging galaxies. Astronomers once believed that collisions within the solar system were unimportant today, but one event we will study is the crash of a comet into Jupiter in 1994. Possibly the most important large impact on Earth was the one that caused the extinction of the dinosaurs 65 million years ago, which is a topic we will study in detail.

This class is aimed at non-science majors. It will emphasize the scientific method and means scientists use to determine what we know about collisions in space. The only math skills required are those you should possess upon entry to the university: some simple algebra, the use of scientific notation, and how to interpret graphs.

Class Hours

Lectures: 11:00am - 12:15pm, Tuesdays and Thursdays, CSS 2400

Contact Information and Office Hours

Instructor: Dr. Melissa Hayes-Gehrke
office: CSS 1233
phone: x5-5099
office hours: Mon 11am - 12pm, Tue 3 - 4pm

TA: Ms. Elyse Casper

office: CSS 0228
phone: x5-1566
office hours: Wed 12 - 2pm
Please feel free to email either the instructor or TA to arrange appointments at other times to discuss the class.


Two books are required for the course. We will be reading Night Comes to the Cretaceous (abbreviated NCC) cover to cover as one of the primary topics of the course. The Cosmic Perspective (abbreviated CP) will be used to cover basic scientific topics and tools and to provide information about the other course topics.


There will be nine homework assignments for the course. The homeworks will be based on material from both the lectures and the reading assignments. Only the eight highest homework grades will be counted. (Course grading is explained in the next section.) If you fail to turn in one homework, it will count as your lowest homework. Homework are due at the beginning of lecture on the dates indicated on each homework. Detailed solutions to the homeworks will be handed out immediately after they are due. For this reason, late homeworks will not be accepted. Homeworks will count toward 33% of your grade.

In-Class Activities

There will be one in-class experiment (on Tuesday, February 15, 2005) that will include a short write-up. The experiment and associated write-up will count toward 4% of your grade. For this class, we will meet in room CSS 1109.

We will watch movie excerpts in-class on Thursday, March 3, 2005. Following the excerpts, you will complete a worksheet on the material in the movie excerpts and turn it in at the beginning of the next lecture, Tuesday, March 8, 2005. This write-up will count toward 4% of your grade.

There will be an in-class discussion of the book Night Comes to the Cretaceous on Tuesday, March 15, 2005. You will be discussing the book in small groups and answering questions about the book. The write-up for this activity will be handed in at the end of the class. This activity will count toward 4% of your grade.

Exams and Grading

Credit will only be given for those answers on homeworks and exams that answer the question asked. Partial credit will be given if the answer was on the right track but incomplete. Credit will not be given simply for effort.

There will be one midterm, one quiz, and one final. The midterm will be on Thursday, March 17, 2005. The quiz, which will take half the class period, will be on Thursday, April 21, 2005. The final exam will be held on Monday, May 16, 2005, from 8:00 - 10:00 am.

On the exams, you will be allowed to use a calculator. No cell phones, computers, PDAs, or other devices will be allowed.

Grading will be as follows:

Letter GradeMinimum Course Grade Percentage
The scale for the letter grades above may be curved if the exams or assignments prove more difficult than expected. If that is the case, the minimum course grade percentages may be lowered; they will never be raised.

How to Do Well in This Course

The key to succeeding in this course is to budget your time so that you are able to keep up with the readings and complete the homework assignments. Reading the designated sections before class will allow you to connect the class material to the book and give you a greater understanding of the material.

Try to budget time to start the homeworks before the night before they are due. If you read over and begin each problem, you will figure out which problems present difficulties for you that you might want to ask questions about.

Since this is a 3-credit class, you should be spending 9 hours a week on it. Here is a suggested budget for your time on a weekly basis:
3 hoursAttending lecture
0.5 hourSkimming reading assignments before lecture
3 hoursReading assignments
2.5 hoursHomework and visiting office hours
To excel in the course, you need to keep up with the work and the reading assignments. In particular, if you skim the reading assignments before lecture, you will know what material covered in the lecture you can read about in more depth in the textbook - that means you do not have to write down the lecture notes verbatim.

Also, something that I cannot emphasize enough: please come ask questions in office hours! Topics that you are welcome to ask questions about:

The homeworks are a third of your grade for this class -- take advantage of office hours so that you excel on them and boost your grade!


University regulations for excused absences and academic honesty apply strictly in this class. Please review them in the schedule of classes. If you must be absent for a university-approved athletic event or religious observance, please contact me by Drop/Add Date, September 13, 2004, to make appropriate arrangements. If you will be absent for any other reason and wish to receive full credit for assignments you will miss, you must contact me before missing class to discuss missed material and to arrange to bring a valid excuse.

Academic Integrity

The process of scientific inquiry and education depends on the integrity of all participants. Students are expected to adhere to the Honor Pledge listed on the Student Honor Council website ( Academic dishonesty consists of cheating, fabrication, facilitation, and plagiarism (see the website for a complete description of each type). Academic dishonesty will not be tolerated in this class.

I encourage students in the class to discuss the assignments. However, be very careful that when you write up the assignments, you do so independently and do not copy the work of a classmate.

Be careful when writing up your assignments to avoid plagiarizing the book. If you must quote the book, indicate the quote and the source of the text. However, only a small fraction of your answer should be quoted material: most of it should be in your own words.


The schedule of topics, readings, and due dates for assignments is on the next page. The readings should be completed prior to class. I strongly suggest you at least skim them before class; you certainly will need them to complete the homeworks.

On the schedule, NCC stands for Night Comes to the Cretaceous and ECP stands for The Essential Cosmic Perspective.

The book discussion write-up will be due at the end of the class period. The movie excerpt write-up and cratering experiment write-up are due as indicated on the schedule.

Th 1/27 Course introduction; NCC: Prologue;
scientific notation; units ECP: 1.1-1.2, Apdx. C
T 2/1 Solar system overview; NCC: Ch. 1;
craters in the solar system ECP: 6.1, pp 133-143
Th 2/3 Gravity; energy; NCC: Ch. 2;
impacts; crater types ECP: 4.3-4.4
T 2/8 Formation of the NCC: Ch. 3; HW 1
solar system ECP: 6.2-6.4
Th 2/10 Leftovers from the NCC: Ch. 4;
formation of the solar system ECP: 9.1-9.2
T2/15In-class Cratering ExperimentNCC: Ch. 5HW 2
In room CSS 1109
Th2/17Erasing cratersNCC: Ch. 6;Experiment write-up
ECP: 7
T 2/22 Tunguska; comet collision NCC: Ch. 7;
with Jupiter ECP: pp 248-249
Th 2/24 Other giant impacts NCC: Ch. 8;
in the solar system ECP: p 157
T3/1Real threat of impacts;NCC: Ch. 9;HW3
protection strategiesECP: pp 251-252
Th3/3In-class activity:NCC: Ch. 10
Earth Impacts in the Movies
T3/8Alvarez TheoryNCC: Ch. 11;Movies write-up
ECP: pp 157-159, 259-250
Th 3/10 Other mass extinctions; are they periodic? NCC: Ch. 12
T 3/15 In-class discussion of book NCC: Ch. 13 HW 4
discussion write-up
Th 3/17 Midterm
Spring break
T 3/29 Light; temperature; energy; spectra ECP: 5.1-5.2
Th 3/31 Star formation; solar structure ECP: 12.1, 10
T 4/5 Evolution of low-mass stars ECP: 12.2 HW 5
Th 4/7 Evolution of high-mass stars 12.3-12.4
T 4/12 White dwarfs; neutron stars; black holes ECP: 13 HW 6
Th 4/14 Milky Way galaxy ECP: 14.1-14.2
T 4/19 Do stars collide? ECP: 11.2-11.3, 12.4 HW 7
Star clusters; close binaries
Th 4/21 Quiz; other galaxy types ECP: 15.1
T 4/26 Galaxy clusters; galaxy formation ECP: 15.3
and collisions
Th 4/28 Active galactic nuclei; Milky Way's ECP: 15.4, 14.4,
black hole; lookback time pp 387-388
T 5/3 Doppler effect; distance chain; ECP: pp 116-117, HW 8
Hubble Law 15.2
Th 5/5 Rotation curves; dark matter; ECP: 16.1-16.3
large scale structure
T 5/10 Big Bang ECP: 17
Th 5/12 Big Crunch? review ECP: 16.4, p 449 HW 9
M 5/16 Final Exam, 8 - 10 am

The image in the background of this page was taken by Debra Meloy Elmegreen and colleges at Vassar College and the Hubble Heritage Team at the Space Telescope Science Institute.