Using the Web

Go to the Chandra X-ray Observatory’s “Variable Stars” Web page ( Do the two exercises on Cepheid variable stars, which ask you to estimate their changes in brightness. You might want to look at Appendix 6 to review apparent magnitudes before you do the projects.
Go to the American Association of Variable Star Observers (AAVSO) website ( What does this 100-year-old organization do? Read about the types of intrinsic variable stars. Click on “Getting Started.” If you have access to dark skies, you can contribute to the study of variable stars. Go to the page for observers ( and click on each item in the “For New Observers” list, including the list of stars that are easy to observe. Assemble a group and observe a variable star from this list. (Another option is to join AAVSO’s project searching for novae, at
Go to the University of Washington’s “Properties of Planetary Nebulae” Web page ( and do the lab exercise.
Go to the Hubble Space Telescope’s planetary nebula gallery ( Find an example of a nebula that shows clearly each type of symmetry: spherical, bipolar, point-symmetric (see question 43 for an explanation of these types of symmetry). Print each of the three images you choose, and label the type of symmetry each one represents. For all three nebulae, identify the location of the central star. For bipolar symmetry, draw a line that shows the axis about which the nebula is symmetric. For point symmetry, identify several features that are symmetric across the location of the central star.
In the Hubble telescope news archive, look up press releases on planetary nebulae ( and white dwarf stars ( Pick a story for each. What observations were reported, and why were they important?

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