The greatest distance we have dealt with in these labs so far is the distance to the dwarf planet Eris. In terms of light travel time the distance from the Sun to Eris is about 9 light hours. No one really knows how to define the boundary of our Solar System but Eris may be representative of objects in the outermost parts. The next nearest major object is the star Proxima Centauri. In terms of light travel time Proxima Centauri is 4.3 light years away. Think about that a little bit. It takes light 9 hours to get from the Sun to Eris and 4.3 YEARS to get to the Sun's nearest neighbor.

The purpose of this lab is to teach you how astronomers find distances to nearby stars. The specific method we will explore is called parallax. Parallax forms the basis for finding distances to most astronomical objects. You will learn how parallax is used through hands-on activities and you will apply what you have learned to determine distances to some objects.


  1. Read the background material by clicking on the topics listed on the menu on the left side of this page. For a given topic there may be multiple pages each of which can be accessed using the navigation buttons arranged across the top of each page.

  2. Answer the questions as they appear by filling in the form fields on the page. Click Save for each question. To change your answer click "Change Answer" and re-save. When you have answered all of the questions click the button labeled "Problems". A confirmation page will appear with all your answers imbedded. Any questions you did not answer will appear in red. To go back and answer those questions use "Back" button at the bottom of the page or use the right mouse button and choose "Back". If you close the confirmation page before printing all of you work will be lost!

  3. You will need to print a confirmation page and turn it in to your instructor. You can do this by clicking on the "Submit" button at the bottom of the page and then using the right mouse button and selecting "print".

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