To encourage students to observe the quality of the night sky and to determine the number of stars that can be seen from their local area.
Ask students how many stars there are outside at night. Accept all estimates and record them on the chalkboard. Ask how they could go beyond guesses and estimates. Tell students that they are going to devise a way to count the stars in the sky. If you have access, tell them their data will become part of a national, on-line collaboration.
Ask students to explain the phrase "Twinkle, Twinkle, Little Star". Ask them what "twinkling" means. Explain to students that only stars twinkle--the moon and planets do not. As a group, make the predictions as suggested on the activity sheet. Pick a time for students to make night-time observations of stars. Then proceed to the bottom half of the activity.
Materials
Procedure Have students measure the width of their "Observing Device" and then cut the tube so that its length is three times its width. The tube will show just a small section of the entire sky. Explain to students that it would take 144 such tubes to cover the whole sky.
Plan a time for students to take a "Star Census". Review with students how to do the counting. If possible, it would be interesting to have students make these observations in different locations (near a city or out in the country) and at different times (when there's a bright moon and when there's no moon). For younger students, you can use fewer observations. Just remember that each observation represents 1/144th of the sky. If students make only 6 observations, they would multiply the total number of stars observed by 24 (which is 144 divided by 6).
Interdisciplinary Connection
Many poets have written about the night sky. Encourage students to do a literature search for poems about starry nights. As an alternative, after completing Live From the Stratosphere, you could have them rewrite "Twinkle, Twinkle..." in "Scientifically Correct" language, applying as many of the new concepts they've acquired in an intentionally light-hearted parody of the old nursery rhyme. "Scintillate, scintillate, giant Globe of Gas..." might give them the idea, but we're sure your students can do better than the LFS Development Team! You'll find literary sidebars throughout this Guide, and can share them with your students. You can see poet Gerard Manley Hopkins playing with words to match his perceptions of the stars. Encourage your students to do likewise, and share their work with the LFS project, via mail or e-mail, when you return the Teacher and Student Evaluation forms.
LFS On-line Connection
If you're on-line, check out the more detailed suggestions about how your students can share their observations with other sites. Look for the "Star Census" area. With access to the World Wide Web, they'll literally get their names on the map and see their data appear as part of the LFS on-line materials.
We'll be featuring star-counting and light pollution activities during the Night Flight to the Stars program, airing live beginning at 20:00 Eastern on October 13th.
KAO Connection
The KAO flies above most of the earth's atmosphere, higher than most water vapor and clouds. At 41,000 feet, the stars do not twinkle. The sky is much clearer and more steady above most of the atmosphere.
Have you ever wondered what makes a star twinkle? On the next clear night look at a bright star.
A star is a point of light. It is so far away that even the largest telescope cannot show the star's disk. The atmosphere changing between the star and your eye causes starlight to twinkle.
Make these predictions about twinkling:
a. Do stars lower in the sky or higher, twinkle more?__________
b. Do stars twinkle more on a windy night, or a still night?__________
c. Do stars twinkle more at sea level or on a mountain top?__________
d. Do stars also change color as they twinkle?__________
Hint: Count star blink rates to answer the first question.
Share your data with students in other locations to answer the remaining questions.
"Seeing" is the term astronomers use to describe the steadiness of images. "Seeing" is best when the twinkling is least. When the seeing is good, astronomers can collect better data about the brightness and color of distant stars and galaxies.
Try this experiment to measure the number of stars you can see.
1. Make an "Observing Device" from a bathroom tissue or paper towel tube. Measure the diameter of your tube. Cut its length to be three times its diameter. Through the tube, you will see only a small portion of the sky. It would take 144 tubes to cover the whole sky.
2. One by one, face in each of the 4 compass directions (North, South, East and West).
3. Hold the tube 3/4 of the way up from the horizon in each direction and count the number of stars seen through the tube. Hold the tube half-way up from the horizon and repeat the count. Repeat the procedure again with the tube pointed a third of the way up. Repeat observations for the other directions. Record your data below.
| Area | 3/4 up | 1/2 up | 1/3 up | Total |
| North | ...... | ...... | ...... | ...... |
| South | ...... | ...... | ...... | ...... |
| East | ...... | ...... | ...... | ...... |
| West | ...... | ...... | ...... | ...... |
| Total | ...... | ...... | ...... | ...... |
| Grand | ||||
| Total | ...... | ...... | ...... | ...... |
4. Add up the number of stars for all 12 sightings. If it takes 144 tubes to cover the sky, then you have observed 1/12th of the sky. Multiply your sub-total by 12 to estimate the total number of stars in the sky. Estimated total number of stars:_________ (includes the stars above and below the horizon)
5. Add up and compare the three measurements in each direction.
Why do you see more stars in certain directions?
