Objectives

In this activity, students discover that, because the planets orbit the Sun, they too move through Earth’s starfield.

• construct a Solar System scale model
• use planet orbital positions to determine where the planets are in Earth’s sky tonight
• learn more about individual planet characteristics

Schedule

About 50 minutes

Materials
For each student
1      Activity Sheet 6, Parts A and B
1      *astronomy journal
1      *Planetary Orbit Chart
1      *Star Time Chart

For each team of four
1       bead, blue, small
1       bead, orange, small
1       bead, teal, small
1       bead, white, small
1       bead, yellow, large
1       bead, yellow, small
1       grease pencil, black
1       SkyCaps, laminated, set/12
1       Solar System Orbit Map

For the class
1 set  Planet cards
1       *SkyCaps, paper, set/12

Vocabulary
planet
Solar System

1. Make a copy of Activity Sheet 6, Parts A and B, for each student. Make paper copies of the SkyCaps for each student as well. Make a copy of the Planet cards for each team of four.
2. Students will need their Star Time Charts and Planetary Orbit Charts from Activity 4. Each team of four will need a set of laminated SkyCaps, a Solar System Orbit Map, a set of Planet cards, a grease pencil, a metric ruler, and beads to represent the Sun and planets in their models.

Background Information

Our Solar System consists of the Sun, the nine planets that surround it (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto), and their moons. It is considered "flat" in that the planetary orbits occur generally on one plane (see Figure 6-1).

<Insert Figure 6-1: Our Solar System>

The planets roll around on this imaginary flat plate like marbles on a table top. (Only Pluto’s orbit is significantly tilted.)

Of the eight planets besides Earth, three (Uranus, Neptune, and Pluto) are too faint for easy observation. A fourth, Mercury, is too close to the Sun for students to find easily. The remaining four planets are discussed in this activity.

Venus is the brightest of the planets in Earth skies. Because it is located between the Earth and Sun, Venus always appears in the western sky after sunset or in the eastern sky before sunrise. Venus is white in color with no cloud features in visible light. Sometimes the planet shows a phase like the moon does.

Mars is much fainter than Venus and distinctly reddish in appearance. When Mars and Earth are on the same side of the Sun and close together, you can sometimes see white polar caps and dark surface markings on the Red Planet with a small telescope.

Jupiter is bright and distinctive in Earth skies. It is yellowish-white in color. With binoculars, you might glimpse up to four of its large moons. With a small telescope, you can see the planet’s banded atmosphere and its moons easily.

Saturn is fainter than Jupiter, but easily identified. It is also a yellowish-white color. With a telescope of 35x power or greater, you can identify the planet’s beautiful rings and maybe even its biggest moon, Titan.

In Activity 1, students may have observed bright objects in the night sky that shone with a steady light (in contrast to the "twinkling" stars) and recorded their locations in their SkyCaps. In this activity, students will identify these objects as planets. They will also determine when they can see certain planets in the sky.

Teaching Suggestions

1.
Begin by asking students to recall any bright objects they observed in Activity 1 that were not identified in their SkyCaps. Ask, What do you think these objects were?
&
Students may know that they were planets.
&

Write planet on the board. Then ask, Who knows what a planet is?
&
A planet is a celestial object that orbits a star, such as our Sun.
&

Explain to students that they will learn more about the planets in this activity.
&
You may choose to distribute the sets of Planet cards now, or at the end of the activity.
&

2.
Divide students into teams of four and distribute a copy of Activity Sheet 6, Parts A and B, and a set of paper SkyCaps to each student. Distribute the set of laminated SkyCaps, Solar System Orbit Maps, grease pencils, and beads to each team.

Ask, Are the planets stationary like the Sun? How do they move?
&
Most students will know that the planets revolve around the Sun, just as Earth does.
&

Explain that all the planets, including Earth, revolve around the Sun. Each travels at its own speed and at its own distance from the Sun.
&
Remind students that a planet’s path around the Sun is called its orbit.
&

Go on to explain that we refer to all the planets and the Sun collectively as the Solar System.
&
Write Solar System on the board.
&

Explain that they will now build and use a model of our Solar System.

3.
Tell students to follow instructions in Step 1 on their activity sheets to set up their maps and add the Sun and Earth model beads.

<Insert Figure 6-2: The Solar System model.>

Once they have set up their Solar System Orbit Maps, have students complete Steps 2 and 3 on the activity sheets.
&
Students should look at the Planetary Orbit Chart for this month and notice that a number between 0 and 360 has been assigned for each planet. As needed, show students how to use these numbers to place the planets in the correct locations along their orbits for tonight. Point out that the beads students are using as models are true to neither size nor color.
&

4.
Ask, Which constellation is each planet located in tonight? Have students recall Activity 4 in which they looked from the Earth, through the Sun, and on to the Zodiac band in order to determine which constellation the Sun could be seen in from Earth that month. Have students use the same procedure here.
&
Remind students that they are observing the planets from Earth. As needed, show them how to look from Earth to a planet and on to the Zodiac constellation in which they could observe the planet that night.
&

<Insert Figure 6-3: Determining which constellations the planets are in tonight.>

5.
Ask students to record the constellation locations for each planet in the chart on their activity sheets.

Tell students to mark the locations of the planets on their SkyCaps for tonight using a grease pencil.
&
Help students as needed to use the Star Time Charts to identify and label the SkyCaps for tonight between 6:00 PM and 6:00 AM.
&

Students should now study the SkyCaps to figure out the correct times to look for the planets tonight.
&
They can do this by noting in which caps the marked planets appear above the horizon.

Remind students that planets that are up in the daytime are difficult or impossible to see.
&

Tell students to record the observation times in the chart on their activity sheets.

Also, have students prepare a set of paper SkyCaps showing the positions of the visible planets. They can take these home tonight and look for the planets indicated (see Science at Home).

6.
After determining the planet locations for tonight, ask, Where do you think the planets will be one month from now? One year from now?
&
Answers will vary.
&

Prompt students to use their Planetary Orbit Charts to locate where the planets will be one month and six months in the future. Then have students move their planet beads to their new positions on the map.

7.
Have students review the information on their Planet cards and respond to the questions at the bottom of their activity sheets.
&
Some of the questions require outside research. Allow time for students to consult necessary resources.
&

8.
Finally, have students turn to their astronomy journals. Ask each student to write a description of how to identify a planet in the night sky in his or her journal.

A school-yard model of the Solar System, featuring students as the planets and Sun, can help students visualize planetary relationships. Extrapolating from the Solar System Orbit Map data, use chalk to create a scaled model showing the orbit of each planet you can accommodate in your space. (A scale of 10 million km/1 step may work well.) Have students walk the orbits of the planets they represent, stopping at each Earth year.

Return all materials to the kit. Students should put their activity sheets and blackline masters in their Astronomy Portfolios.

Have students take their prepared paper SkyCaps home. Challenge them to see if they can find the planets outside on the next clear night. Remind them that planets do not appear to twinkle as stars do.

Activity Sheet 6, Part A: Planet Watch

The ancient Greeks called the planets “wandering stars.” In this activity, you will discover where the planets wander in the sky.

1.  Put the Solar System Orbit map on a table. Make sure the tabs are still up on the edge of the map so that the Zodiac band is visible all around. Place the Sun bead (large yellow) in the center of the map, and an Earth bead (small blue) on today’s date in its orbit.

2.  Choose beads to represent Venus, Mars, Jupiter, and Saturn.

3.  Look up the planet locations on the Planetary Orbit Chart. Use the data to place the planets in the correct places for tonight.

<Insert Figure AS6-1: A Solar System model>

Activity Sheet 6, Part B: Planet Watch

4.  Look from the Earth to each planet and on to a constellation in the Zodiac band. Record the constellation location for each planet in the chart below.

5.  Locate the SkyCaps for tonight at 6:00 PM, 8:00 PM, 10:00 PM, 12:00 midnight, 2:00 AM, 4:00 AM and 6:00 AM. Use a grease pencil to draw the planets on the SkyCaps in which they appear above the horizon. On the chart, record the times when each planet is visible.