The Universe at Your Fingertips • Astronomical Society of the Pacific

Comets, Asteroids and Meteors • E3

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What’s This Activity About?Halley’s Comet is a “short period” comet, with an orbit extending just beyond the distance of Neptune from the Sun. By modeling its orbit with a sequence of images, students can observe that the comet’s tail only begins to develop inside the orbit of Jupiter. They will see that the comet speeds up as it nears the Sun, and that the tail al-ways points away from the Sun. Even though Halley will not return to the inner solar system until 2061, other comets may approach the Sun in the near future, and they will follow the same pattern demonstrated here.

What Will Students Do?Students cut out images of Halley’s comet moving in its orbit around the Sun. Putting the images in sequence, they create a “flip book.” Students can observe the com-et’s motion, its changing speed around the Sun, and the development and direction of its tail.

Tips and Suggestions• Do not tell the students what properties to look for.

After they use the flip books, ask them to form small groups and discuss their observations. Ask the groups to develop hypotheses for what they see. Bring the groups together to share results, and lead the discus-sion to sunlight, gravity, and the solar wind.

• Note that Halley’s Comet does not orbit within the plane of the solar system, as the flip book images might suggest. Students may even ask if Halley would ever collide with a planet, like Comet Shoemaker- Levy 9 did with Jupiter in 1994. Halley’s orbit, like that of most comets, is highly inclined to the plane of the planets. The comet spends most of its orbit far “below” the planets (for those of us in the Northern Hemisphere!)

Make a Comet Motion Flip BookActivity E3

Grade Level: 4–6

Source: Reprinted by permission from Return of the Comet by Dennis Schatz, Copyright ©1985 by Pacific Science Center. Book is no longer in print. No reproduction of this activity of any sort is permitted without written permission from Pacific Science Center (200 Second Ave. N., Seattle, WA 98109-4895. www.pacsci.org), except that Pacific Science Center grants permission for individuals purchasing the Universe at Your Fingertips to reprint the Flip Book pages for classroom use only.

Concepts• Comets • Solar Wind• Orbits

Inquiry Skills• Observing• Inferring• Visualizing

Big Ideas• Interactions • Patterns of Change

What Will Students Learn?

The Universe at Your Fingertips • Astronomical Society of the Pacific

Comets, Asteroids and Meteors E3 • Make a Comet Motion Flip Book

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Comet Motion Flip BookActivity Guide

From Return of the Comet by Dennis Schatz (Pacific Science Center), © 1985 Pacific ScienceCenter. Reprinted by permission. Book is no longer in print. No reproduction of thisactivity of any sort is permitted without written permission from the Pacific Science Center(200 Second Ave. N., Seattle, WA 98109), except that Pacific Science Center grantspermission for Astronomy from the Ground Up participants to reprint the Flip Book pagesfor educational purposes.

Adapted by Anna Hurst© 2006, Astronomy from the Ground Up • Astronomical Society of the Pacific,390 Ashton Ave., San Francisco, CA 94112 • www.astrosociety.org/education.html

Type of Activity: Make-and-take

Set up Time: 10 minutes

Time to Do: 20 minutes

Audience age: 8 years and older

Group size: varies

What’s This Activity About?

Halley’s comet is a “short period” comet, with an orbit extending just beyond the distance ofNeptune from the Sun. By modeling its orbit with a sequence of images, participants can observethe behavior of a comet as it orbits the Sun.

Materials

• One set of flip book images for each participant (separate file on AFGU website)• Scissors• Rubber bands or envelopes to keep the pieces together

The Universe at Your Fingertips • Astronomical Society of the Pacific

Comets, Asteroids and Meteors E3 • Make a Comet Motion Flip Book

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2 Comet Flip Book © 2006 Astronomy From the Ground Up updated May 2006

Setting Up the Activity

You will need to make copies of the flip book pages and put out scissors. The Flip Book pagesare available as a separate file on the AFGU website (www.afguonline.org -- accessible to AFGparticipants)

Suggestions for Introducing the Activity

What is a comet? Have you ever seen one? We are going to explore the behavior of Halley’sComet as it orbits the Sun. Halley’s Comet was last visible from the Earth in 1986. We will see itagain in 2061. How old will you be then?

Before the invention of movies, people made pictures appear to move by taking manyphotographs, one right after the other, and stapling them together. By flipping through thepictures quickly, the objects appeared to move. In this activity, we will see the motion of Halley’sComet using a flip book.

Doing the Activity

Have participants cut out the drawings on the two flip book pages. They should be careful to cutalong the lines. Then have them stack the pages together in numerical order with number one ontop. Fan them out slightly to make them easier to flip through. They should flip through the pagesseveral times to be sure the flipping motion is smooth. Then have them flip through one moretime and challenge them to try to identify at least three things about comets and their motion.

Do not tell participants what properties to look for. After they use the flip books, you could havethem form small groups and discuss their observations. Ask the groups to form hypotheses forwhat they see.

Give everyone a rubber band or envelope to keep the flip book pages together on the way home.

Wrap-up

Bring the groups together to share results. Lead the discussion to sunlight, gravity and solar wind.Let the groups come up with at least three features of the comet’s motion on their own. Below aresome of the points they might bring up and some more background information on each.

• The flip book lets you see that the comet only forms a tail when it nears the Sun. Thecomet begins to melt as it approaches the orbit of Jupiter at about 800 million km (500million miles). The frozen gases are released to form the coma, which increases in size asthe comet approaches the Sun.

• Most comets form a tail as they approach the orbit of Mars at about 250 million km (150million miles). The tail usually increases in size until just after the comet’s closestapproach to the Sun, when the reverse process begins.

• The most dramatic and unexpected observation that can be made from the flipbook is thatthe tail of the comet always points away from the Sun. The solar wind, which always

The Universe at Your Fingertips • Astronomical Society of the Pacific

Comets, Asteroids and Meteors E3 • Make a Comet Motion Flip Book

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3 Comet Flip Book © 2006 Astronomy From the Ground Up updated May 2006

blows away from the Sun, causes the tail to always point away from the Sun in the sameway that smoke from a smoke stack moves away from the direction of the wind.

• Notice when you flip the book that the comet moves slowly in its orbit when it is far fromthe Sun and quickly when it is near to the Sun. It is easy to understand why, if we look athow the pull of gravity between the Sun and the comet works. Gravity is the force thatmakes any object attract all other objects. The pull of the Earth’s gravity keeps youattached to the Earth and the Sun’s gravity keep the Earth and Halley’s comet in orbitaround the Sun, The pull of gravity is greater when the two objects are closer together.Since the comet is being pulled harder when it is near the Sun it will travel faster thanwhen it is far from the Sun.

• The comet orbits in a clockwise direction, opposite planetary motion – the planets orbitthe Sun in a counterclockwise direction.

• The extreme ends of the orbit of Halley’s comet are beyond Neptune and within theEarth’s orbit, respectively. Some comets reach much farther out into the solar system,beyond Pluto.

Note that Halley’s comet does not orbit within the plane of the solar system, as the flip book maysuggest. Participants may even ask if Halley could ever collide with a planet, like Shoemaker-Levy 9 did with Jupiter in 1994. Halley’s orbit, like that of most comets, is highly inclined to theplane of the planets. The comet spends most of its orbit “below” the planets (for those of us in theNorthern Hemisphere), and only peeks into the path of the planets near the Sun.

The path of Halley’s comet intersects the Earth’s orbit at two points. The debris it leaves in itspath therefore causes meteor showers on Earth twice a year. These are the Eta Aquarids (April 21– May 12) and the Orionids (October 15 – 29). The Fire and Ice activity explores the relationshipbetween comets and meteor showers in more depth.

Complimentary Activities:

• Kitchen Comets• From Fire to Ice: Modeling the Comet Orbits

The Universe at Your Fingertips • Astronomical Society of the Pacific

Comets, Asteroids and Meteors E3 • Make a Comet Motion Flip Book

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The Universe at Your Fingertips • Astronomical Society of the Pacific

Comets, Asteroids and Meteors E3 • Make a Comet Motion Flip Book

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