Movement of Constellations in the Night Sky

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/

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/