The Undiscovered Planet

Activity:
Students use contrived star field photographs to find a planetary object.

Science Standards:
Nature of Science and Patterns of Change

Objectives:

  • The student will find a planetary object using two overlaid star fields.
  • The student will determine the distance to the object using trigonometric parallax.
  • Materials:

  • photocopies of two star fields (star plates)
  • metric ruler
  • bright light source (overhead, window, light table suggested)



  • Introduction:
    Clyde Tombough discovered Pluto in the winter of 1930. He made this discovery by comparing two photographs of the stars taken several months apart. His strategy was to look for the star-like object that had "moved" during the time between the photographs. This strategy also demonstrated that meteors are phenomena that occur in the atmosphere and that comets are much more distant than the Moon.

    Directions:
    1. Align stars in Star field One over Star field Two.
    2. Circle the "star" is found in Star field Two not yet seen in Field One.
    3. Align stars in Star field Two over Star field One.
    4. Circle the original position of the moving "star."
    5. Measure the change in position.
    6. Using the given equation, determine the distance the object is from Earth.
    7. Identify the object.



    Given Information Needed:
    The star fields are imaged 12 hours apart; subsequently, the observer has changed her position by the diameter of the Earth; 7,928 miles. For these photographic plates, 1 cm equals 0.00122 degrees.

    equation 1: Angular change in position = Measured Change (cm) * 0.00122 /cm

    equation 2: Distance from Earth = 57.3 * 7928 miles (angular change in position)

    Important Note: This activity was created and tested in its entirety by the genius of Jeffrey Lynn Hopkins from Columbia, South Carolina. It appears here in an abridged form such that it can be completed in less than 30 minutes. The complete materials are extensive enough to be used as an entire classroom unit. He has also published a similar activity for a hypothetical binary star system.

    INSERT STAR FIELD IMAGE #1

    FIGURE 105

    HERE
     
     
     
     
     
     
     
     
     

    INSERT STAR FIELD IMAGE #2

    FIGURE 106

    HERE