ALEX Lesson Plan

In this lesson, students will examine time lapse photos and videos to see the movement of stars during the night. Students will use star wheels to track the visibility of constellations throughout the year and graph the number of days a constellation is visible each month. Using data from the graphs, they will collaboratively construct a large-scale model of the sun, Earth, and constellations to better understand the role Earth’s movement and axial tilt play in the visibility of stars. Finally, students will draw a diagram and write an explanation of the apparent movement of stars using data from the graphs and class model.

This lesson results from the ALEX Resource Gap Project.   

Globe

Basketball or another ball to model as the sun

Copy of Sky & Telescope sky map printed on cardstock for each student

Copy of Sky & Telescope star wheel sleeve printed on cardstock for each student

Stapler and staples

Paper/Pencils for each student

Copy of Movement of Stars Checklist (from the attachments section) for each student

For each group of 2-3 students:

• Large sheet of black construction paper
• White crayon or chalk
• Copy of graph handout (from attachments section)
• Colored pencils or markers for making graph

Optional materials:

• Printed pictures of Ursa Major, Cygnus, Pegasus, Aquarius, Leo, Orion, Virgo, Capricornus, and Sagittarius from https://stardate.org/nightsky/constellations. (Only 1 picture of each constellation is needed, or you can have students can access these pictures directly from the website.)
• Printed picture of Ursa Minor from https://commons.wikimedia.org/wiki/File:Dipper_constellations_(PSF).png
• Extension: copies of NASA “fortune teller style” star finder for the current month from https://spaceplace.nasa.gov/starfinder/en/ for each student.
• Intervention: copies of "The Ever-Changing Sky" article for each intervention student (http://www.readworks.org/passages/ever-changing-sky).  The article is available for a free download by creating a free account on ReadWorks.org.

Teacher computer with internet connection, printer, and projector for accessing and displaying websites:

• Pictures of Constellations - https://stardate.org/nightsky/constellations
• Picture of Ursa Major and Ursa Minor - https://commons.wikimedia.org/wiki/File:Dipper_constellations_(PSF).png
• Intervention article - http://www.readworks.org/passages/ever-changing-sky
• Teacher Background information - https://www.universetoday.com/85730/do-stars-move/
• Teacher Background information - http://curious.astro.cornell.edu/about-us/120-observational-astronomy/stargazing/how-the-motion-of-the-earth-affects-our-view/734-why-do-different-stars-appear-with-seasons-beginner
• Photo of star trail - https://en.wikipedia.org/wiki/Star_trail#/media/File:All_In_A_Spin_Star_trail.jpg
• “Arrow of Time” time lapse star video - https://www.youtube.com/watch?v=nam90gorcPs
• Star Wheel pattern - http://www.skyandtelescope.com/astronomy-resources/make-a-star-wheel/
• Crash Course Kids video - https://www.youtube.com/watch?v=BbzCA0Lgf3Y
• Optional extension activity - https://spaceplace.nasa.gov/starfinder/en/
• Optional extension lesson - https://betterlesson.com/lesson/635651/constellation-patterns

Devices with Internet connection (computers or tablets) for each group of 2-3 students (optional – resources can be printed if these are not available)

• Constellation pictures and research - https://stardate.org/nightsky/constellations
• Picture of Ursa Major and Ursa Minor - https://commons.wikimedia.org/wiki/File:Dipper_constellations_(PSF).png
• Intervention - https://www.youtube.com/watch?v=MZffhapfOgg
• Intervention - http://www.ducksters.com/science/physics/constellations.php
• Intervention - http://www.readworks.org/passages/ever-changing-sky (if you want students to access the article online rather than printing it)
• Acceleration - http://www.astromax.org/con-page/con-12.htm

Background information for the Teacher

Earth is constantly in motion, rotating on a tilted axis as it revolves around the sun. The sun and other stars appear to move across the sky each day and night, but this daily movement of the stars is caused by Earth’s rotation. 

Named groups of stars are called constellations. There are 88 officially named constellations. Most constellations received their names long ago as part stories from Greek or Roman mythology, but a few constellations have been named more recently. Constellations help people locate stars in the sky, but the stars in the constellations are not connected in any physical way. Using named constellations is a way people can find and discuss the location of stars easily.

The same constellations are not visible at every location on Earth, and many constellations are only visible during certain seasons. Because Earth is tilted on its axis and we live in the northern hemisphere, we can see the northern circumpolar constellations (Auriga, Camelopardalis, Cassiopeia, Cepheus, Draco, Lynx, Perseus, Ursa Major, and Ursa Minor) all year. These stars are always visible to us because they are aligned with Earth’s axis of rotation. Since the North Star is directly in line with Earth’s axis, all other stars appear to circle the North Star each night as Earth rotates. Because Earth is simultaneously revolving around the sun as it rotates on its axis, constellations in different parts of the sky are only visible during certain seasons. When the sun is between Earth and a constellation, the constellation cannot be seen because sunlight prevents us from seeing it during the day, and the darkened half of Earth is facing away from the constellation at night. For a complete explanation of the apparent motion of stars and constellations, visit https://www.universetoday.com/85730/do-stars-move/ and http://curious.astro.cornell.edu/about-us/120-observational-astronomy/stargazing/how-the-motion-of-the-earth-affects-our-view/734-why-do-different-stars-appear-with-seasons-beginner.

Prerequisite Information for Students

Students should already understand that day and night are caused by Earth’s rotation rather than the movement of the sun. They should also understand that the sun is an average star, but it appears larger and brighter to us because of its proximity to Earth. They should know that seasons are caused by Earth’s tilt on its axis as it revolves around the sun. 

Teacher Preparation

Preview websites and videos. Print one copy of each of the constellations listed in the materials section or provide devices for each group so they can access the pictures online. Make copies of the Sky Map and Star Wheel on cardstock for each student. Make copies of the graph handout (in attachments section) for each group of 2-3 students and movement of stars checklist for each student.

Before/Engage:

1. Show students image of star trail at https://en.wikipedia.org/wiki/Star_trail#/media/File:All_In_A_Spin_Star_trail.jpg. Have students turn and talk to a partner about what they think the picture shows and how it was made. 
2. Make a T-chart on the board with the headings “I Know…” and “I Wonder…”  Have students share their prior knowledge and questions from their discussion and write their ideas on the chart.
3. Show the first 2 minutes of the Arrow of Time video at https://www.youtube.com/watch?v=nam90gorcPs. (If necessary, explain that time lapse photography is a method of taking pictures at designated intervals of time and then putting the pictures together to create a video that makes slow events appear to happen faster.)  
4. Have partners turn and talk about the video. Add their ideas and questions to the T-chart. Make sure questions such as “Why are the stars moving?” and “Why do the stars appear to circle a certain point?” are included on the chart.

During/Explore & Explain:

1. Ask students if they have ever spent time looking at the stars and if they have ever witnessed the stars moving. They may have heard of sailors using stars for navigation in history lessons, but how could they use them for navigation if they move? What causes the stars to move?
2. Connect the movement of stars to the movement of the sun. While students may not have noticed the motion of the stars throughout the night, they certainly have noticed the movement of the sun during the day. Ask students whether the sun is really moving across the sky every day. (Earth is moving rather than the sun; Earth’s rotation causes night and day as well as the appearance that the sun moves across the sky.) Explain that the sun is the closest star, so it appears to be the brightest, but it is nonetheless an average star. Other stars in the sky have the same properties as our sun. While the stars remain in the same positions in the sky relative to Earth, Earth’s rotation makes the stars appear to move across the sky each night just as the sun appears to move across the sky in the daytime. (Depending on the students’ understanding of stars, you can choose to explain the proper motion of stars or omit it. Because other stars are so far away from us, we cannot perceive this proper motion in our lifetimes. It may be unnecessarily confusing to introduce the proper motion of stars at this time.)
3. The rotation of the Earth explains stars’ movement across the sky, but why do they appear to circle one star in the sky? Remind students that Earth is tilted on its axis and show this with a globe. Point out that we live in the northern hemisphere of Earth, so we can see the stars that are located north of the equator; we cannot see every star in the sky because the rest of the Earth is in the way.
4. Explain that constellations are groups of stars that form a recognizable pattern. These stars have remained in the same arrangement for thousands of years, and ancient people named the constellations to make it easier to find specific stars in the sky. Stories told about these groups of stars helped people remember the names and locations of the constellations, so they could be located and used for navigation. Through repeated observations over time, a sky map was created. 
5. Give each student a copy of the star chart and star wheel from Sky & Telescope http://www.skyandtelescope.com/astronomy-resources/make-a-star-wheel/.  Have students cut out the disk and star wheel. Fold the blank white rectangle at the bottom of the star wheel behind the wheel and staple it to create a pocket for the sky map. Explain that this wheel shows which stars are visible in the northern hemisphere on any night of the year. A different sky map would be used for people in the southern hemisphere.
6. Tell students they will be working in groups of 2-3 students to figure out which constellations they could see in the night sky at different times of the year. Assign each group a constellation from this list:

• Ursa Major
• Cygnus
• Pegasus
• Aquarius
• Leo
• Orion
• Scorpius
• Virgo
• Sagittarius
• Ursa Minor (the little dipper) – This constellation is not named on the sky map, so have students write it in on their charts. The tail of Ursa Minor is the North Star.

7. Give each group the following materials: a printed picture of the constellation they will be investigating or provide the web links from the materials section so students can access the pictures online, a large sheet of black paper, white chalk or crayon, graph handout from attachments section, and markers. Students will draw and label the constellation on the black paper with the white chalk or crayon.

8. Model how to use the star wheel to see how many days of a given month a particular constellation is visible and graph that information on the handout. Have students reach a consensus on whether they will count the days when the constellation is only partially visible. Give students time to make a graph for their constellation. (List months on the x-axis and graph the number of days the constellation is visible on the y-axis.  You may choose to have students make a bar graph or line graph. With either type of graph, students will see that circumpolar constellations are visible all year while other constellations are only visible during certain months.) If some groups complete their graphs faster than others, have them research their constellation as https://stardate.org/nightsky/constellations and add facts to the bottom of their constellation poster.

9. Hang posters and graphs around the classroom so they are visible by all students. Debrief by asking the following questions:

• Which constellations are visible all year?
• Which constellations are visible in only some seasons?
• During which seasons is your constellation visible?
• Why do you think some constellations are visible all year, while others can only be seen in certain seasons?
• In the picture we examined at the beginning of the lesson, all the stars seemed to move around a central point.  Where do you think this point is on your sky map and why?

Add students’ answers and additional questions to the T-chart.

Explain/Elaborate:

1. Show Crash Course Kids Constellation Location video:   https://www.youtube.com/watch?v=BbzCA0Lgf3Y
2. After watching the video, ask students why all stars are not visible all the time. Add their responses to the T-chart.
3. Tell students that they are going to arrange the constellation posters so they model the location of stars in the sky relative to the sun. Place a ball in the middle of the room to represent the sun. Ask students how they can use the graphs they created to figure out where the constellations are relative to the sun. Guide their thinking with these questions:

• If we can see some constellations all year, what does that tell us about their location relative to Earth and the sun? (Since they are visible from the northern hemisphere all year, they must align with Earth’s axis of rotation. These constellations should be hung from the ceiling.)
• How can we use the globe to figure out which location would represent summer and winter in the northern hemisphere? (The northern hemisphere of Earth is tilted toward the sun in summer and away from the sun in winter. Use the globe to model this as you walk around the “sun.” Hang the constellations most visible in summer and winter on the opposite walls indicated by your model.)
• If we know where Earth is in the sky for summer and winter, how can we figure out where to put the constellations most visible in spring and fall? (Fall follows summer, and spring follows winter. Therefore, you can figure out the direction Earth is traveling around the sun by walking from “winter” to “summer.” The season on the path from winter to summer is spring; the season on the path from summer to winter is fall. Hang the constellations most visible in spring and fall on the appropriate walls.)

4. Have students take a “stargazing” walk around the classroom to view the constellations from the perspective of Earth traveling around the sun. Have them explain to a partner why some constellations are visible only at certain times of the year while others are visible all year.

5. As a summative assessment, have students draw a diagram of Earth in its orbit around the sun and the constellation their group investigated. Then they will write a paragraph explaining how the constellations visible in the night sky change during a single night and over the course of the year.  Have them use evidence from the graphs created during the lesson as evidence to back up their explanations. Use the attached "Movement of Stars Checklist" to evaluate their diagrams and written explanations.

Optional Extension: Have students make NASA “fortune teller style” star finders for the current month of the year and use them to find constellations in the sky tonight! https://spaceplace.nasa.gov/starfinder/en/

Formative: Note student contributions to the class chart, discussion, and creation of the class model as well as their participation in creating the constellation picture and graph in small groups.

Summative: Use the attached "Movement of Stars Checklist" to evaluate students' diagrams and written explanations.

Have students research the difference between astronomy and astrology using information from the American Association of Amateur Astronomers at http://www.astromax.org/con-page/con-12.htm.  Then have them show the similarities and differences in a Venn diagram and share their learning with the class.

Students may also research individual constellations and the mythology behind constellation names, creating a digital presentation or book about the constellations.  

Kara Nelson’s “Constellation Patterns” lesson at https://betterlesson.com/lesson/635651/constellation-patterns provides students additional opportunities to research star movement and engage in fact-based arguments. Students can use the resources linked in this lesson for additional research.

Preview or review information about constellations and the movement of objects through the night sky with these resources:

• Crash Course Kids Introductory Video on Constellations (https://www.youtube.com/watch?v=MZffhapfOgg)
• Ducksters: Astronomy for Kids site: http://www.ducksters.com/science/physics/constellations.php
• 4th-grade level article from ReadWorks.org (http://www.readworks.org/passages/ever-changing-sky). This article provides background knowledge on how things in the sky appear to change due to Earth’s rotation and revolution around the sun.

Assign student graphing groups strategically, pairing students needing extra help with peer tutors.