ASTR 220 Collisions in Space

Fall 2004


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: Monday 3-4pm, Wednesday 2-3pm

TA: Ms. Laura Brenneman

office: CSS 0222
phone: x5-2693
office hours: Monday and Wednesday 1-2pm
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.

Please note: The instructor plans to require The Cosmic Perspective for an ASTR 100-level course next semester; please keep this in mind if you wish to sell your copy of the book back to the bookstore at the end of the term.


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 32% of your grade.

In-Class Activities

There will be one in-class experiment (on Tuesday, September 21, 2004) that will include a short write-up. The experiment and associated write-up will count toward 4% of your grade.

We will watch a video in-class on Tuesday, September 28, 2004. Following the video, you will complete a worksheet on the material in the video and turn it in at the end of class. 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 Thursday, October 7, 2004. 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 two midterms and one final. The midterms will be on Tuesday, October 12, 2004, and Tuesday, November 9, 2004. The midterms will be based on material covered both in lecture and in the assigned readings. The second midterm will test only the material covered since the first midterm. The final exam will be held on Monday, December 13, from 8:00 - 10:00 am. The final exam will be cumulative.

Grading will be as follows:

Minimum course grade percentage for the letter grades: 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.


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.

T 8/31Course introduction.CP 1; NCC Prologue
  Astronomy overview.  
Th 9/2 Terrestrial planets: craters. NCC 1, 2
T 9/7 Erasing of craters. CP 10.1, 10.3-10.6
  Age determination from craters. NCC 3
Th 9/9 Solar system formation. CP 9.1-9.5; NCC 4 HW 1
T 9/14 The leftovers: asteroids, comets and meteorites. CP 13.1-13.4,
    13.6: Comet Tails and Meteor Showers;
    NCC 5
T 9/16 Shoemaker-Levy 9 impact with Jupiter CP 13.6: SL9 Impacts on Jupiter;
    NCC 6
T 9/21 In-class Cratering Experiment hand-out; NCC 7 HW 2
Th 9/23 Other impacts: formation of Moon, NCC 8
  Mercury, Venus, Uranus, rings.  
T 9/28 Video: Crater of Death NCC 9, 10 Experiment
Th 9/30 Alvarez theory of dinosaur extinction. CP 13.6: Impacts and Mass Extinctions,
    The Mass Extinction, Controversies and
    Other Mass Extinctions; NCC 11
T 10/5 Are mass extinctions periodic? CP 13.6: The Asteroid Threat; HW 3
  What is the real threat of impacts? NCC 12
Th 10/7 Class discussion of book. NCC 13
T 10/12 Midterm 1
Th 10/14 Stars: formation and stellar structure. CP 17.1, 17.2, 15.1-15.4
T 10/19 Stellar evolution of low mass stars: CP 17.3
  planetary nebulae, red giants.  
Th 10/21 Stellar evolution of high mass stars: CP 17.4 HW 4
T 10/26 White dwarfs, neutron stars, black holes. CP 18.1-18.4
Th 10/28 Types of binary stars. CP 16.4 HW 5
T 11/2 Close binary evolution: CP 17.5, 18.5
  novae, Type Ia supernovae, GRBs  
Th 11/4 Star clusters. Do stars collide? CP 16.5-16.6 HW 6
  Blue stragglers.  
T 11/9 Midterm 2  
Th 11/11 Structure of the Milky Way. Local Group. CP 19.1-19.4
T 11/16 Other types of galaxies. Clusters. CP 20.1-20.2
Th 11/18 Do galaxies collide? Mergers. CP 21.3 HW 7
T 11/23 Active galactic nuclei. CP 21.5, 19.5
  Does the Milky Way have a black hole?  
Th 11/25 Thanksgiving break
T 11/30 Hubble Law. CP 20.3-20.4 HW 8
Th 12/2 Structure of the universe: CP 22.5
  voids and bubbles.  
T 12/7 Beginning and end of the universe: CP 23, 22.6
  Big Bang and Big Crunch?  
Th 12/9 Review   HW 9
M 12/13 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.