The actual discovery of extrasolar planets (or exoplanets) is relatively new with the first such observation occurring in 1994. since then this branch of research in astronomy has grown dramatically. This exercise will introduce students to this area of study--the techniques that may be used to find exoplanets, a brief overview of what is now known, a simulation to acquaint students with how the transit method works, and some plans for future research projects.
A. Getting Ready
1. Print out a copy of these worksheets for each member of the lab group, unless your instructor has already made copies for your use.
2. At the top-right corner of the first page, write your name and the names of the persons in your lab group. Place an asterisk by your name for identification purposes.
B. General Exoplanet Information
3. Go to ExoplanetMain.html and read the introductory information. Click on the link for "more info" and also check out the Kepler mission site.
4. Next go to http://cfa-www.harvard.edu/planets/ , the "Extrasolar Planets Encyclopedia" site.
|Star Data||Exoplanet Data|
|Name||Mass (solar mass)||Apparent Magnitude||Mass||Semi-major Axis (AU)||Orbital Period (yr)|
C. Transit Method Simulation
5. At Transit-1.html begin the "Finding Exoplanet" simulation. First time through, do the default star (#1). Print out enough copies of the last page of the simulation for each member of your lab group. Then go back and run the simulation again for two more stars printing out the last page, if possible, in each case.. (Only one of these stars may be one of those for which an exoplanet cannot be "observed." If this is the case simply record its number here along with its spectral type.) Locate and copy the appropriate information in the chart below.
|Star Number||Probability of Finding Exoplanet||Is the Exoplanet in the Habitable Zone?|
D. More Exploration of the Transit Method
6. A triumph of the transit method occurred in 1999 when the light curve of the star HD 209458 was shown to indicate the presence of a large exoplanet in transit across its surface from the perspective of Earth.(We still await results from the Kepler Mission or other projects for evidence that Earth-size planets exist around stars other than the Sun.) In addition to providing a measure of the orbital period of the exoplanet about its parent star, the light curve also provided data useful for finding other information about the exoplanet such as its radius. Subsequent spectroscopic studies with the Hubble Space Telescope have even indicated that the exoplanet's atmosphere must have sodium vapor in it.
Apparent Mag.: 7.65
|Source: Cody, Ann Marie & Sasselov, Dimitar D. The Astrophysical Journal, 569, 451-458 (2002); "Extra-solar Planets Catalog," http://cfa-www.harvard.edu/planets/HD209458.html .||Source: Brown T., et al. The Astrophysical Journal, 552, 699 (2000); available through the "Extra-solar Planets Catalog," http://cfa-www.harvard.edu/planets/papers/HST-HD209458.pdf .|
7. Above are some facts about the star and its exoplanet and a refined light curve as recorded by the Hubble Space Telescope. The upper-left corner at the beginning of the drop in the light intensity curve occurred just as the leading edge of the exoplanet began to move across the star and the upper-right corner is just as the last edge of the exoplanet leaves from being in front of the star.
[Useful Data: Rsolar = 6.9599 X 108 m; Msolar = 1.989 X 1030 kg; RJupiter = 1.43 X 108 m; MJupiter = 1.899 X 1027 kg]
8. Turn in your worksheet and the printouts of the results of your simulation calculations. Staple them together with the worksheet on top.
Roger A. Freedman & William J. Kaufmann III. Universe, 6th ed. Freeman, 2002.
William Zeilik and Stephen A. Gregory. Introductory Astronomy and Astrophysics, 4th ed. Fort Worth, Texas: Saunders, 1998.
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Created and maintained by: Richard L. Bowman (last updated: 18-Apr-04)