In this lab we are going to study some of the most distant objects known to astronomers: quasars. In the early days of radio astronomy, surveys of the sky gave rise to catalogues listing the positions of objects whose nature was unknown, similar to the "nebulae" that confounded optical astronomers earlier in the century. Most sources of radio noise could not be positively associated with any optical source. However, two entries (3C 48 and 3C 273) were identified with starlike images on photographs. For that reason, the name "quasi-stellar radio source" was chosen to describe them. This was abbreviated to the name we know them by today, quasars.

In this lab you will learn about quasars, some of the most distant known objects in the universe. Astronomers' knowledge of quasars is based on being able to determine distances to them. You will use the concept of the Doppler effect (you were introduced to this concept in the Binary Stars lab) to determine distances to quasars. In the process you will learn about the extreme properties of these enigmatic 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. Click on the menu item "Problems." A window should open at the bottom of your screen with the questions.

  3. Answer the questions by filling in the form fields on the computer.  Hit the button labeled "Submit" when you are done. A confirmation page will appear with all your answers imbedded. Be careful not to close the problems window until you are finished and want to submit or your answers may be lost and you will have to reenter your answers.

  4. Check over the confirmation page to make sure that you are happy with your answers. If you need to change your answers go back to step 3 and re-submit. We will only grade the last form you submit.

    Good Luck!