Notes: A Star-tling Discovery
 
Key Concept  
Whenever you describe something that is moving, you are comparing with something that is assumed to be stationary, or not moving. Imagine yourself in an observatory where your vision of the sky was limited to the two boxes below. Look at the night sky on two different days. Use your knowledge of Frame of Reference to answer the questions.
 
 http://www.space.com/php/multimedia/imagedisplay

Until 1930, astronomers thought that the planet Pluto was just another star. Then they looked at the two photographs of this “star” that were taken 24 hours apart. What they saw led to theorize that Pluto is a planet, not a star.
 

The photographic plates that show Pluto's movement compared to stars, which are much more distant and remain comparatively fixed at the same time on separate nights. Credit: Lowell Observatory

1.  Write the title of this worksheet in your spiral.
2.  Write the Statement in A.  and your description.
3.  Write the Questions
     A.  Describe the location of the celestial body(Pluto) for each picture.
 
     B. Write the questions  and answers in your spiral.
1. What happened to Pluto from the twenty third of January to the twentyninth of January? 
Answer:
 
2. What frame of reference did you use to describe the change in Pluto?
Answer:.
 

3. Is this frame of reference also moving? If you think so, use another frame of reference to describe its motion.
Answer:
 

4. Why do you think these photographs helped astronomers realize that maybe Pluto was a planet and not a star? (Think about this:  The closest star is so far way, it appear not to move at all.)
Answer: