12.425 | Fall 2007 | Undergraduate

Extrasolar Planets: Physics and Detection Techniques



Physics I: Classical Mechanics (8.01), Single Variable Calculus (18.01)

Course Description

This course covers the basic principles of planet atmospheres and interiors applied to the study of extrasolar planets (exoplanets). We focus on fundamental physical processes related to observable exoplanet properties. We also provide a quantitative overview of detection techniques and an introduction to the feasibility of the search for Earth-like planets, biosignatures and habitable conditions on exoplanets.

Further Background

This course is a systematic introduction to the fundamental concepts and principles of the field of exoplanet detection and characterization. The basic exoplanet detection methods are covered, based on the underlying physical concepts. Physical principles behind planet characterization are explored, and tied to observations and interpretation of exoplanet properties such as composition and temperature. Weekly problems sets are assigned, and include exercises related to using real data on exoplanets to derive their physical properties such as mass, radius, density, temperature or composition. Exoplanet research is a young field in planetary science and the material presented in the course covers the major techniques and methods used by exoplanet researchers.


  1. An introduction to the current state of knowledge and ongoing research in exoplanet detection and characterization.
  2. The development of analytic skills to:
    • Formulate and apply equations to measure exoplanet masses, radii, and semi-major axes from astronomy data sets.
    • Formulate and apply equations to infer an exoplanet interior composition and atmosphere composition from astronomy data.
    • Read graphs, judge the data quality, and interpret the meaning.
  3. The ability to think critically and the habit of doing so actively at all times.

Learning Objectives

  1. Summarize the physical concepts behind five different exoplanet discovery techniques.
  2. Derive and apply equations to measure a planet’s radius, semi-major axis, and orbital inclination from a planet transit data set.
  3. Derive and apply equations to measure a planet’s mass and semi-major axis from an exoplanet radial velocity data set.
  4. Calculate a planet’s mass and radius given a homogeneous planet of a single composition with a given equation of state.
  5. Derive the 1D, plane-parallel radiative transfer equation. Use approximate solutions to this equation to explain the origin of exoplanet atmosphere absorption lines.
  6. List Earth’s biosignatures with a discussion of the significance of each one.

Textbooks and Class Handouts

The topic of exoplanets is so new and fast-paced that no textbooks exist. Instead we will use the book:

de Pater, Imke, and Jack J. Lissauer. Planetary Sciences. Cambridge, UK : Cambridge University Press, c2001. ISBN: 9780521482196.
This book is recommended and not required.

An additional supplementary book is:

H. Karttunen, et al. Fundamental Astronomy. New York, NY: Springer-Verlag, c2007. ISBN: 9783540341437.
This is an introductory astronomy textbook.

To compensate for the lack of an appropriate textbook, there will be regular reading handouts in lectures. These handouts include conceptual descriptions as well as analytical derivations. It is expected that regular attendance in lecture will offer the opportunity to pick up these handouts. Should you miss a handout, they will also be posted online.

Class Participation

This is a discussion-based and problem-solving-based class. Over half of the class time will be spent problem-solving in small groups or in class discussion. In addition, your questions and comments are extremely valuable. Discussions during class time are especially appropriate given the lack of an exoplanet textbook. Discussion is highly encouraged to fill gaps in the lecture material, to guide the pace of the class, and for you to inquire about the meaning, relevance, and importance of lecture material.


Approximately weekly problem sets will be handed out on Thursdays and due the following Thursday before class.

A note on submission of work. Collaboration on homework sets is permitted. The manner in which you present your work, therefore, is just as important (and in some cases more so) than the final answer. Be sure to delineate each step along the way. Show a clear and logical approach to your solution. This will make your problem sets both a better reference to you and easier for partial credit (if so deserving) for grading.


Grading Scheme

Problem sets 30%
Test 1 20%
Test 2 20%
Final exam 30%
Total 100%

Course Info

As Taught In
Fall 2007
Learning Resource Types
Problem Sets
Lecture Notes