# Counting the Stars

### Creighton University

This activity was developed be Elizabeth Frank for Project SPICA, August 1991. In it, students practice a technique in their classroom which can be used on the real night sky to estimate how many stars are visible to the naked eye.

In this activity, students will....

1. predict how many stars are visible in the night sky
2. estimate the number of stars in the sky by averaging the number of stars in a small portion of the sky and extrapolating from their data
3. check their predictions

Materials needed:

• typing paper (28cm by 22cm)
• tape
• pencils
• three large sheets of opaque butcher paper
• sticky dots or push pins
• calculators

Procedure:

1. Make three sky charts as follows: if your classroom has windows, poke 10-25 holes randomly on a piece of butcher paper. On the second piece, poke 20-30 holes, and make 30-50 holes on the third piece. It is not necessary to know exactly how many holes you punch. Hang the butcher paper in front of the windows. The light shining through the holes will simulate stars.
2. If your classroom lacks windows, randomly scatter sticky dots on three pieces of butcher paper as above. These will represent stars. Hang the butcher paper on the classroom wall.
3. Have each student roll a sheet of typing paper into a tube 28 cm long and 4 cm in diameter. Fasten with tape. If the tube's diameter is not exactly 4 cm, measure and record the exact diameter.
4. Have students stand about 5 meters from the butcher paper, and sight through the paper tube toward one of the charts. Count and record the number of stars seen. Repeat for each chart.
5. Add together the number of stars from each count and divide by three for the average (As).
6. Calculate the number of stars using the following formula:
7. Take the tube home and repeat steps 3-6 looking at the real night sky. Calculate the number of stars visible.

(Note: the actual number is around 6000, but remember that about 50% are hidden below the horizon at any given time)

This activity has been copied, with permission, from the Nebraska Earth Science Education Network server to ours, to allow faster access from our web site.
We encourage you to explore the original site.