Lunar and Planetary Institute






Polaris

Activity: It's Still Polaris


Investigate!
Children ages 9–13 observe the changing night sky over the course of an evening and chart the circumpolar stars as they traverse the sky in a progression around Polaris. Using their knowledge of Earth's day/night cycle, they infer the cause of the changing star positions.

Before You Begin

Spring and summer months offer optimal night sky viewing of Polaris in the northern hemisphere. Check your local sky chart for visibility of the Dippers and note how the little Dipper changes position during the planned viewing nights and times. Plan for a clear night to have the children observe the sky; a weekend night is recommended so that the children can stay up later.

Make a copy of the chosen night's sky chart on a transparency. Then, on a blank transparency, place a dot to mark Polaris' location. Make sure the dot is placed where there is ample room for the children to draw the Little Dipper several times as it moves during the course of the evening

The Activity

Revisit the SkyTellers story of Negah and Polaris with the children.

  • Do they think they can find Polaris, the North Star, in the night sky?
  • Which star groupings will help them find Polaris?
  • What do the children predict will happen with the stars they observe in the night sky, based on what they learned in the story?

You may want to enter the conversation by reviewing the causes of day and night and helping them use this to make their predictions.

Share with the children that they will observe the night sky to see if their predictions are correct.

Distribute the SkyChart and ask the children to locate the Big and Little Dippers. Use the overhead transparency of the night sky to help them locate the star patterns. Have the children connect the stars in the Dippers with a marker. Help them locate the two stars on the far right side of the Big Dipper bowl and, with their finger, draw a line toward the Little Dipper handle.

Ursa Minor Lesser Bear - Polaris (North Star) - Ursa Major (Greater Bear)Explain that they will observe the night sky to see if there are changes in the positions of the Dipper stars, paying particular attention to Polaris, the bright star at the end of the Little Dipper handle (make sure the children are able to find Polaris). The children can use their charts at home to help orient them when they view the night sky.

Provide each child with a sheet of transparency film, a cardboard frame, and a marker and explain that they will record their observations of the night sky.

Have the children tape the transparency film across the frame so that it makes a window. Using the transparency with Polaris already marked, guide them in placing a dot on their frame. They can label their dot "Polaris."

On a clear night, have the children go outside with a parent or sibling and locate the Big Dipper, Little Dipper, and Polaris. Once they have found the stars, they should carefully hold their frame up at arm's length so that Polaris is positioned behind the dot they made.

Transparency with Polaris markedHave them draw a line parallel to the horizon. Next have them draw the outline of the Little Dipper on the film. This takes a steady hand or a helper! Inside the bowl of the Little Dipper, have them write the time of their observation. Before they leave, the children should place a pair of shoes in the exact location and position they were standing so that they can return for later viewing visits.

Every hour, for the next four or more hours, have the children return to the identical location and viewing position. They should repeat the process of finding Polaris, carefully holding their transparency so that their central dot covers Polaris and the line marking the horizon parallels the actual horizon. They should draw the outline of the Little Dipper and record the time in the Dipper bowl. In later viewing, the Little Dipper may go off the page - but that's okay! If they have made careful observations and drawings this will reinforce the idea that the stars do move across the night sky!

After the children have collected their observations, invite them to share their discoveries.

  • Were their earlier predictions about the movements of the stars correct?
  • Did any of the stars appear to travel across the sky? (Yes, all the other stars in the sky - except Polaris - appeared to move)
  • In which direction did they appear to travel? (They appeared to move in a counter clockwise motion) Why? (Because the Earth spins counterclockwise)
  • Did any star(s) appear "fixed"? (Yes, Polaris is stationary)
  • How do they explain the apparent movement of the stars? (Earth's rotation) Do the stars "actually" move? (No, they only appear to move)
  • Why does Polaris appear "fixed"? (Polaris appears stationary because our axis points directly toward it, making it the apparent "center" of the night sky in the northern hemisphere; just as the center of a wheel does not appear to move even while the spokes all around it do)
  • How do they predict the stars would have moved over the entire course of the night? (The stars continue in an apparent counterclockwise circular path around Polaris, with some "moving" out of view at certain times of the night)

The children should have observed that the Little Dipper "swung" around Polaris. Ask them to develop a hypothesis, based on what they know about how Earth moves, to explain their observations.

Extensions

Children can view "star trails" at this site or here. Star trails, made by exposing film for several hours over the course of the night, are graphic evidence of the apparent motion of stars.

The Web site Interactive Sky Chart offers an excellent opportunity for the children to view and manipulate the night sky over a longer (time-elapsed) period. This will reinforce understanding for those that may have had difficulty viewing or understanding the apparent motion of the stars.

More Activities

Last updated
December 13, 2011

 

Who?
Ages 9–13

How Long?
Two approximately 60-minute sessions, separated by an evening of night sky viewing

What's Needed?

For the activity:

•  Sheet of stiff plastic transparency film
•  Marker

For each child:

•  Sheet of stiff plastic transparency film Cardboard or poster cutout to frame the transparency
•  Tape
•  Fine-tipped marker
•  Extra pair of shoes
•  Copy of a local Sky chart.

Connections to the National Science Standard(s)

Standards A&D (grades K–4): Ask questions, predict, and communicate explanations about the apparent circum-polar movement of objects in the night sky. Answer those questions by making observations and employing simple tools to gather data. Understand that objects in the sky have locations, movements, and patterns of movement that can be observed and described.

Standards A& D (grades 5–-8): Ask questions, predict, and communicate explanations about the apparent circum-polar movement of objects in the night sky. Answer questions by making observations and employing simple tools to gather data.

Understand how objects in the solar system have regular and predictable motion, such as the apparent circum-polar movement of objects in the night sky.