Drifting Among the Stars
MAY 2, 2006
MAY 3, 2006
They are up there. It says so in all the books. But how can you distinguish planets from the background of stars. The answer is simple. Planets move. In fact the word planet is derived from the Greek word, planktos that meant drifter. To find a planet you need to distinguish this spot of light by its movements across the background of an unchanging field of stars.
Click HERE to view the answer.
Materials
Prints of both dated starfields
Overhead transparency scrap (1/4 of sheet)
Black marker (that writes on transparency sheet)
Tape
Questions
1. How were the planets distinguished from the surrounding starfields? (Over time the planets move in relation to the background stars. When a point moved in relation to its background starfield, it was identified as a planet.)
2. How many planets were captured in this image pair? (Three planets).
3. Suppose the difference in captures was one week instead of one day. Do you think this would affect the ease of uncovering planets? Explain. (Yes. In the longer time, the planet's position would probably have a greater change, making it more easier to distinguish from the unchanging background of stars. However, if the time was too long, the images might not be logically paired as the same sky object.).
Campaigning for Planetary Status
Do you think that Pluto deserves the rank of planetary body? Use print and web resources to research the controversy surrounding Pluto's status as a planet. How does Sedna, Xena, and other distant objects in our solar system change our understanding of what planets are and how they should be defined? Develop a classroom campaign for keeping Pluto a planet and/or for awarding planetary status to large objects of the Kuiper belt and Oort Cloud.
Using Real Images
Check out the sequence of images shown on page 45 of this issue of Discover. Draw a straight line between the two brightest points of light in the first image. Draw a similar line in the third image. How did Sedna's position change in reference to these stars in this short time?
Make a Model
Create a model of the solar system that illustrates the relative distance of the sun to the following; Pluto (3 billion miles), Xena (10 billion miles) and the edge of the solar system (about 5 trillion miles).
