Planetarium Activities For Successful Shows

Strange Planets

by Alice Enevoldsen, Alan Gould, Toshi Komatsu, and Steven W. White 

A collaboration of Pacific Science Center and the Lawrence Hall of Science


Cover photo adaptation of Milky Way photo by Carter Roberts.

NASA Kepler spacecraft.
Launched March 6, 2009. Artwork courtesy NASA.
This material is based upon work supported by the National Science Foundation under Grant Number TPE-8751779 and by NASA under Grant NAG2-6067 (NASA Kepler Mission Education and Public Outreach). There was also support from the NASA Astrobiology program. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Science Foundation or NASA.

Copyright © 2008, 2009, 2011 by The Regents of the University of California, and 2007 by the Pacific Science Center

This work may not be reproduced by mechanical or electronic means without written permission from the Lawrence Hall of Science, except for pages to be used in classroom activities and teacher workshops. For permission to copy portions of this material for other purposes, please write to: Planetarium Director, Lawrence Hall of Science, University of California, Berkeley, CA 94720.

The original edition printing of the Planetarium Activities for Successful Shows series was made possible by a grant from Learning Technologies, Inc., manufacturers of the STARLAB Portable Planetarium.

Planetarium Activities for Successful Shows

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Strange Planets Planetarium Show


    Media List
Recommendations for Using the Script
Variations for Show Length
Planetarium Show Script
    The Spectroscopic Method
    Stars With Planets
    Habitable Zones & Kepler’s Laws
    Transiting Planets
    Finding an Earth-like Exoplanet
About Exoplanets



“Strange Planets” is a fifty-minute planetarium program about finding extrasolar planets, focusing especially on the transit method & the Kepler Mission. It was originally designed for a sixth-grade audience. The primary goal of this planetarium show is for the audience to understand the difficulties of finding extrasolar planets, and to understand how those difficulties are overcome by modern astronomy techniques. The audience will consider interstellar distances and grapple with the two challenges of finding extrasolar planets—extrasolar planets are very far away, and are very dim compared to the stars they orbit. We discuss two ways it can be done: through the spectroscopic and the transit methods.

Simple outline:
5 min Intro
10 min Spectroscopic Method
5 min Stars with Planets (Pollux, Alrai)
5 min Kepler’s Laws & Habitable Zones
10 min Transiting Planets
10 min Finding an Earth-like Exoplanet
5 min Kepler star field/Conclusion



Students will…

Introduction Spectroscopic Method Stars with Planets Kepler’s Laws and Habitable Zones Transiting Planets Finding an Earth-like Exoplanet


Figure 1. Rainbow Projector
  1. Rainbow projector

    Use a prism or diffraction grating mounted on a light source, such as a flashlight, overhead projector, or slide projector. Quality of spectrum is better with brighter light source and slit shaped source.

    Easy Alternative: A movie or still image(s) depicting the flashlight/rainbow demonstration ( in AlternativeMedia folder).
Figure 2. Star-planet model—two variations.

The effect is better still if the crank is black or dark colored, with only the star (light) and planet ball white.
  1. Portable star-planet model

    Make a portable star-planet model that the presenter can carry around to demonstrate wobbling motion of a star. The star is a flashlight bulb and the planet a large bead or light-weight ball, such as 3/4” polystyrene sphere. They are mounted on sticks or stiff wire in a way that the model can be easily spun on a handle (e.g. with wire shaped into a crank) and the star is off-axis so it will exhibit wobbling motion (Figure 2). See Strange Planets area of PASS website for more ideas on how to build star-planet models (

    Easy Alternative: a movie of a person operating the portable star-planet model can be played instead of live presenter carrying a real model around.


Make the star-planet distance and the amount of wobble adjustable. Also have option of swapping in two different size planets: large and small.

Figure 3. Fixed star-planet model as orrery.

Figure 4. Planets on clips

  1. Orrery (star-multi-planet model) and light sensor for real-time light-curves
    For the “Transiting Planets” section of the show, you need

    1. a fixed star-multi-planet model with (i) two sizes of planets—interchangeable, and (ii) a way to have planets at different distances from the model star.

    2. a light sensor, interface, graphing software, laptop, and videoprojector for projecting real-time light curves on the dome.
Easy Alternative for Orrery: movie of orrery being used to generate a light curve (, in AlternativeMedia folder).

          For the orrery, here are some ideas for how it can be done:

  1. The portable star-planet model from (2) can be used as a fixed model orrery, as long as it can be mounted as target of the light sensor. Use a 15-25 watt large spherically-shaped light bulb as a light source instead of the flashlight as a model star. A swing-arm lamp serves well for this purpose (Figures 3 and 4). To allow planets to be different sizes and orbit radii, a binder clip, paper clip, and a planet can serve nicely as adjustable distance (figures 4-5).
Figure 5. Closeup of clip for interchangeable planets.
Black duct tape on the clip makes for a
more secure connection to to the wire.

Figure 6. The Walking Orrery: All parts easy to obtain. The light fixture (from hardware store) was filed slightly so that the flashlight would screw into it.

  1. Make a “Walking Orrery” with just one planet (Figure 6). In this variation, the star is a flashlight with a transluscent globe fastened on and attached to a pole that rests on the floor on a spot marked with a masking tape “X.” That’s held by an audience volunteer. A polystyrene planet is put on another pole and held by another volunteer who walks in orbit around the star. The light sensor is mounted on another pole at the same height as the star.
  1. Make a multi-planet orrery from LEGO parts (Fig. 7). See the NASA Kepler website for instructions on how to build one ( Fig. 7 also shows a complete setup of LEGO orrery, star (light bulb), sensor, and laptop with light curve visible.

Figure 7. Real-time light curve setup using LEGO orrery, light sensor and light mounted on physics poles with clamps

Figure 8.
Light sensor stand made of PVC.

As far as light sensor, our field tests were done with a Vernier light probe and Vernier Logger Lite software. The sensor needs to be mounted on a stand at about the same height as the “star” in the star-planet model. There are many types of stands possible. Figure 8 shows one made of PVC, but it can be made of metal wire also. Figure 6 shows sensor mounted on a wood dowel.

Tinker with the software settings so that you get a light curve with easy-to-see characteristics. A 40-second time period for data collection is adequate to generate two curves successively, for side-by-side comparison of different size or different distance planets. The procedure for acquiring the side-by-side light curves is described in the script, using the 1-planet model or the Walking Orrery. Once you get the settings how you like them, save the file and use that to start up the software, so that the settings are automatically right for your program.

Another style orrery—2 planets. This is a prototype for one planned for commercial distribution through Delta Education, Spring 2012. The crank is under the base, below the light. Sensor stand is attached to base at left.

  1. Optional Handouts:
  • Strange Planets take-home handout Side 1 and Side 2 and
  • Exoplanet Size and Orbit Size Lookup Chart
  • .


    Visual Name Filename Source Credit*
    1a-b. Kepler Launch and Dust Cover Ejection (optional movies),;
    NASA/Kepler Mission/Dana Berry
    2. The first extrasolar planet discovered 51Peg.png Debivort
    3. Geoff Marcy GMarcy.png Volker Steger
    4. Spectroscopy (star, telescope, diffraction grating, and absorption spectrum) Spectro.png LHS: A. Enevoldsen/T. Komatsu LHS
    5. Spectroscopy (spectrum shift) (movie) LHS: A. Enevoldsen/T. Komatsu LHS
    Jupiter (has a big wobble) Jupiter.png Cassini Mission - NASA/JPL/University of Arizona
    7. Mercury (has a fast wobble) Mercury.png NASA/MESSENGER Mission - NASA/Johns Hopkins/Carnegie 
    8. Artist’s rendition hot Jupiter (movie or still) or HotJup.png;
    NASA Kepler Mission/Dana Berry (movie); NASA/JPL-CalTech/T. Pyle, SSC (still)
    9. Pot outline for Big Dipper (optional) Pot.png LHS: G. Steerman LHS
    10. Planet with two suns BinaryPlanet.png Tim Jones, MacDonald Observatory 
    11. Sun-Orange Giant-Red Giant RedGiants.png
    12. Top-view diagram of Solar System (optional) SolarSys.png 
    (use full-dome digital version if available)
    NASA/JPL-CalTech: H. Smith/L. Generosa
    13. Habitable zone (movie)
    NASA Kepler Mission/Dana Berry
    14. Johannes Kepler JKepler.png
    Museum der Sternwarte Kremsmünster
    15. 1st Law - Orbits are ovals KLaw1.png LHS: A. Gould
    16. 2nd Law - Equal times/equal areas KLaw2.png Walter
    17. 2nd Law - Elliptical orbit (movie)
    18. 3rd Law - T2 r3 chart KLaw3.png LHS: A. Gould
    19. Transit Light Curve
    NASA Kepler Mission/Dana Berry
    20. Optic Path (optional movie) NASA Kepler Mission
    21. Kepler spacecraft KeplerSpacecraft.png NASA Kepler Mission
    NASA Kepler Mission
    22. Light Curves Kepler 10b, 11bc, 11de, 11fg, 11 LightCurveKepler10b.png,
    LHS: A. Gould/T. Komatsu, LHS
    23. a and b. Size and Distance Lookup Charts LookupChartSize.png,
    LHS: A. Gould
    24. a and b. Artist’s depiction of Earth-like planet (optional) NewEarth1.png,
    LHS: Susan Stanley
    25. a. Kepler’s target area b. CCD pattern c. Kepler 1st light KeplerFOV.png,
    LHS: A. Gould/Carter Robert NASA Kepler Mission
    26. Kepler’s Orbit (movie)
    NASA/Dana Berry
    27. Diversity of Life (movie)
    NASA/Dana Berry
    28. Learn More LearnMore.png LHS: T. Komatsu
    29. Credits Credits.png LHS: A. Gould

    Additional animations and movies can be found at the NASA Kepler website animations page:

    * Media Credits

    Debivort: Wikipedia contributor, Boston, MA
    JPL-Caltech: Jet Propulsion Laboratory, Caltech,
    LHS: The Lawrence Hall of Science, University of California, Berkeley,
    NASA Kepler Mission:
    Sakurambo: Wikipedia contributor
    Walter: Stephan Walter, Switzerland, Wikipedia contributor
    WillowW: Willow, Wikipedia contributor


    Exoplanet Size and Distance Lookup Chart*

    Brightness Drop Planet Size Orbit Time Orbit Distance
    (%) (Earth=1) (days) (Earth=1AU)
    0.01 1.0 25 1/6
    0.02 1.4 50 1/4
    0.04 2.0 100 0.42
    0.06 2.4 150 1/2
    0.08 2.8 200 2/3
    0.10 3.2 250 0.78
    0.12 3.5 300 7/8
    0.14 3.7 350 .97
    0.3 5.5 400 1.06
    0.5 7.1 450 1.15
    0.7 8.4 500 1.23
    0.9 9.5 550 1.31
    1.0 10.0 600 1.39

    * For Sun-like stars

    Download PDF


    Download PDF


    Download PDF

    Recommendations for Using the Script

        We don’t expect the script which follows to be memorized (as an actor might memorize a part) but to be used as a guide in learning, rehearsing, and improving presentations. We recommend that you read the script once or twice, then work with it in the planetarium, practicing the projector controls, visuals, special effects, and music. You should be able to imagine yourself presenting information, asking questions, and responding to participants. For your first few presentations, you can have the script on hand, using major headings as reminders of what to do next.

        The script is organized in blocks or sections. The purpose of these separations is only to help you learn and remember what comes next. Once you have begun a section, the visuals or special effects and your own train of thought will keep you on track. When beginning a new section, make the transition logically and smoothly.

        Directions for the instructor are printed in italics in the side column, the instructor’s narrative is printed in regular type, and directions and questions to which the audience is expected to respond are printed in bold italics. There is no point in memorizing narration word-for-word since what you need to say will depend upon the participants. The language you use and the number and kinds of questions you ask will depend on how old the participants are, how willing they are to respond, and how easily they seem to understand what is going on.

        We believe that the most important elements of the program are the questions and the activities since these involve the audience in active learning. If you must shorten your presentation, we recommend that you borrow time from the narration.

    Variations for Show Length

    The show is intended to be 50 minutes long, including all sections, except for the detailed treatment of Kepler’s Laws. However, many variations and adaptations are possible.

    Length of show in minutes

    50 40 30
    Introduction x x x
    The Spectroscopic Method x x
    Stars With Planets x x x
    Habitable Zones, Kepler's Laws x

    Transiting Planets x x x
    Finding and Earth-like Exoplanet x
    Conclusion x x x


    Boxes like the one to the right are for presenters, and signify when to use a particular digital effect in your planetarium.

    Description of digital effect



    1. Set sky to a time when both Cygnus & Gemini are visible, e.g. May 25, 22:00, local time.
    2. Cue up images & videos.
    3. Rainbow maker ready (diffraction grating & flashlight)
    4. Spinning star-planet models ready. Set up orrery.
    5. Set up Vernier Light sensor, interface, laptop with graphing software, and video projector.
    6. Optional Handouts: Strange Planets take-home handout Side 1 and Side 2 and Exoplanet Size and Orbit Size Lookup Chart
    Load all media for the program, including images and video clips. Set up the sky for the beginning of the program. Use December 1, 2011 as the start date, chosen because it is a time of year when Cygnus, Lyra, and Pegasus are all visible in the sky.


    Planetarium Show Script

    Dim house lights.


    Bring out stars.

    Fade music.
    Hello, and welcome to the ________ Planetarium. Our program is called Strange Planets. But of course, strange is in the eye of the beholder. Any planet might seem strange.

    We have eight planets in the Solar System, all very different and each strange in its own way. We know at least one has life—Earth, a strange planet, partly because of all the strange people on it.

    Are there places other than Earth that could have life?
    Accept answers and encourage discussion with other questions.
    We use the word habitable for a place that can support life.

    People have long wondered…are we alone?
    Point towards starry sky.
    If there are a lot of other planets circling stars out there beyond the Solar System, we could greatly expand the possibilities for finding habitable places.

    There HAVE been planets discovered around other stars. They are called extra-solar planets or exoplanets for short.
    DIGITAL EFFECT: Exoplanets
    Fade on images of exoplanets.
    Do you know how many exoplanets have been discovered?  [Accept answers. As of December 2014, “over 1,700” is correct. See The Extrasolar Planets Encyclopedia at or the New Worlds Atlas at the PlanetQuest website —]
    If possible, show live or recent screenshot of the PlanetQuest New Worlds Atlas page that has up-to-date exoplanet count:

    Optional, if correct answer is not given:

    Raise your hand if you think there are less than 50 planets discovered? Less than 100? Less than 400?

    We’ve discovered over 1,700 [use current planet count] planets outside of our solar system. Most of the extrasolar planets discovered have been quite large—the size of Jupiter or even bigger.
    VISUALS 1a and 1b (optional movies): Kepler Launch and Dust Cover Ejection
    Show movie of Kepler spacecraft launch (2009 March 6) and animation of dust cover ejection (2009 April 7). Alternatively, show some combination of the launch, deployment, and/or dust cover ejection.


    DIGITAL EFFECT: Kepler Mission
    Fade on and scale up an image of the Kepler spacecraft, as well as the constellation outline for Cygnus and the Kepler field of view target area.


    NASA’s Kepler Mission launched in March of 2009. When its dust cover was ejected, it started collecting data on the brightness of 100,000 stars. It is designed to detect evidence of planets that are roughly the size of the Earth and suitable for life!
    DIGITAL EFFECT: End Kepler Mission
    Fade off the Kepler spacecraft and Cygnus and field of view images.

    The Spectroscopic Method

    Finding extrasolar planets is really tough.

    Why do you think finding exoplanets is so hard?  [Extrasolar planets are extremely dim, very close to their stars, and so far away that the star’s glare ruins our chances of seeing the planets.]

    For decades, astronomers had suspected there were extrasolar planets out there, but there was never any proof until 1992.
    Play music. 

    The first exoplanet around a Sun-like star was discovered around a star called 51 Pegasi in the constellation of Pegasus. Here is Pegasus (digital effect "Extrasolar Planets") and here is 51 Peg (digital effect "Locate 51 Pegasus"). 
    DIGITAL EFFECT: Extrasolar Planets
    Turn on an outline of Pegasus. Used to illustrate where the first exoplanet around a main sequence star was discovered.

    DIGITAL EFFECT: Locate 51 Pegasus

    DIGITAL EFFECT: Zoom 51 Pegasus

    VISUAL 2 (still): 51 Pegasi, the first extrasolar planet discovered

    Here we see an artist conception of the planet (visual 2.) It’s an artists concept because it’s impossible for us to actually see the planet, even with out most powerful telescopes.

    To find such planets, we must resort to clever and ingenious methods. Most exoplanets, so far, have been detected by the Spectroscopic Method.

    Fade music.

    VISUAL 3 (still): Geoff Marcy

    Fade off image of Geoff Marcy.

    This is the world’s pre-eminent planet-finder—UC Berkeley astronomer, Geoff Marcy. He and his team pioneered a planet-finding technique called the spectroscopic method. Here is how it works.
    Switch on the flashlight & diffraction grating and beam a rainbow on the audience. Turn a circle and sweep the rainbow over everybody and across the dome.


    Play music.

    VISUAL (alternative movie): Rainbow Movie
    Alternative to live demo of flashlight with diffraction grating, in AlternativeMedia folder

    There is something called a diffraction grating on this flashlight. It works kind of like a prism.

    What happens when light passes through a prism?  [Take any answers.]

    The rainbow you see is called a spectrum. You can see all the colors from the flashlight separately—each one all stretched out.
    Fade music.

    VISUAL 4 (still): Spectroscopy 1, showing a star, a diffraction grating, and an absorption spectrum of the star with lines

    We look at a star with a telescope that has a diffraction grating; the starlight stretches out into a rainbow spectrum. You can see dark lines in the rainbow spectrum where the star is actually missing those colors because different chemicals, like hydrogen and helium and sodium, swallow up those colors. Now here’s the key to planet-finding using the spectrum….
    Turn on the “star” on the wobbling star/planet model and walk around without spinning the star. The star should move very smoothly. Add music.
    Here we have a star with no planet orbiting it.

    Does it seem to you to be moving steadily? [Yes.]

    Now let’s add a planet orbiting the star.
    Start spinning the planet around the star. The star should appear to wobble.

    Play music.

    VISUAL (alternative movie): Wobbling star
    Movie can be played as alternative to showing the wobbling star model live.

    What’s unusual about how is “star” is moving now?  [It appears to wobble.]

    What do you think is causing the star to wobble? [The planet’s gravity is tugging on its star.]

    The planet’s gravity makes the star move back and forth as the planet orbits, but since planets are so much smaller than stars, the wobble is a teeny-tiny wobble.
    Play music. 

    VISUAL 5 (movie): Spectroscopy 2, where the star is wobbling and the absorption lines wobble with it.

    If the star is wobbling towards us and away from us, it affects the rainbow/spectrum of the starlight. When the star moves toward us, all the dark (absorption) lines in the spectrum shift slightly over toward the blue side of the rainbow spectrum. That’s called a blue shift. When the star is moving away from us, all the dark lines shift the other way, toward the red side.

    Guess what that’s called? [Red shift. ]


    Have half the audience clap when the animation shows blue shift and the other half of the audience clap when the animation shows red shift.
    The cause of red shift and blue shift is a lot like what happens when a sound, such as a train or race car, slides down in pitch as it goes by you.
    Play audio sample of a Doppler shift.

    When studying these wobbles, we look for two features—the size of the wobble, and the speed of the wobble.

    What might cause a really big wobble? [A big massive planet, ...or planet very close to the star.]

    What might cause a really small wobble? [A small planet, ...or planet far from the star.]

    It’s the gravity of the planet that makes the star wobble and the force of gravity is stronger if the planet is more massive or closer to the star.

    How about the speed of the wobble?

    What might cause a really slow wobble?  [A slow wobble means the planet is orbiting slowly.]

    The further the planet is from its star, the slower the wobble.

    What might cause a fast wobble?  [A fast wobble means the planet orbits quickly around its star, and hence is closer to its star.]

    If an alien astronomer were watching the spectrum of our Sun, which planet do you think would create the biggest wobble?  [The biggest planet, Jupiter. If necessary, prompt by asking what the biggest planet is. Mercury is the closest planet, but not very big at all. Jupiter’s gravity affects the Sun a lot more than Jupiter’s even though it’s much farther away.]
    VISUAL 6 (still): Jupiter (has big wobble)

    Which planet would make the fastest wobble?
    [Mercury. If necessary, prompt by asking what the closest planet to the Sun is. The amount of wobble would be tiny.]
    VISUAL 7 (still): Mercury (has fast wobble)

    Actually, Mercury would make a fast wobble, but also a very small wobble since it’s not very massive. Most of the extrasolar planets we know of have been found by studying these spectrum wobbles, and they have been quite large—many bigger than Jupiter. Not only that, most of the planet discoveries have been ones that orbit close to their stars. That’s because large wobbles and fast wobbles are much easier to find than small, slow wobbles.

    If a planet is orbiting close to its star, what would that do to the planet’s temperature?
    [It would be hot.]

    Those large planets with close in orbits we often call “hot Jupiters.”

    VISUAL 8 (movie or still): Artist’s rendition of a hot Jupiter

    This is a picture of what a hot-Jupiter extrasolar planet might look like. Of course, we’ve never seen one directly. It might look like Jupiter, but being so hot, it could be a strange planet indeed. In fact, people thought Jupiter-size planets so close to at star would be impossible in light of theories of solar system formation at the time. Theories were shattered.
    Fade off planets.

    Stars With Planets

    In our planetarium sky, there are a couple of stars that have giant-size planets orbiting them, but with Mars-like orbits—farther out from their stars than Earth is from the Sun. They are not hot Jupiters. Are they strange planets? You can see one of those stars year-round in the constellation of Cepheus. To find Cepheus, let’s start with a more familiar group of stars.

    Have you ever seen the Big Dipper before? Can anyone point it out for us? [Take any answers.]

    It has seven bright stars, shaped like a pot with a long curving handle.

    VISUAL 9 (optional still): Pot outline on the dipper stars
    Fade on an outline of the Big Dipper “pot” shape. 

    There it is! Some people think of it as part of a giant ferocious bear. 

    DIGITAL EFFECT (optional still): Bear outline

    DIGITAL EFFECT: Stick Big Dipper

    DIGITAL EFFECT: Locate Polaris

    DIGITAL EFFECT: Locate Alrai

    DIGITAL EFFECT: Stick Cepheus


    DIGITAL EFFECT: End Cepheus 

    The Big Dipper can be used to point to the North Star. See these two stars?

    Indicate the Pointer Stars.
    They’re called the Pointer Stars because they point to the North Star, also called Polaris. It’s always in exactly the same spot in the north. If you can find the North Star, you’ll never get lost.
    Follow the pointer stars to Polaris, and indicate.
    Here’s the North Star! And if you keep going a little farther
    Continue to Cepheus.
    you’ll find this bright star.
    Point to Gamma Cephei (Alrai).
    That star is in the constellation Cepheus, the King. The star called Gamma Cephei, which means “third-brightest-in-Cepheus.” Its Arabic name is Alrai (a.k.a. Errai, or Er Rai). It’s is 45 light-years away, and is a binary star system: two stars revolving around one another every 50 years or so. Imagine having 2 suns in your sky! A strange planet indeed.
    Play music. 

    VISUAL 10 (still): Planet with two suns
    Show visual of binary star system with planet.

    Optional: Hand out Uncle Al’s Kepler Star Wheels (master on Kepler website), have the audience set them for May 25 at 10 pm, and find Alrai (Gamma Cephei) on the star wheel. Explain how to adjust the Star Wheel, and let them know that you’ll be telling them how to get their own copy to make from a web page that you’ll give them.
    The planet is bigger than Jupiter, about 1.5 times Jupiter’s mass, and is going around the larger star of the binary system. It’s year is 2½ Earth years, and a tad bit farther from it’s sun than our Mars is from our Sun.
    Fade off image of planet with two suns.

    Another star with a planet can be found in this very famous winter constellation, Gemini.
    Show artwork of Gemini outline.

    DIGITAL EFFECT: Stick Gemini
    Show only a stick figure of Gemini.

    DIGITAL EFFECT: Locate Pollux
    Place an arrow on the dome to point out the position of Pollux.

    Point out Gemini, with outline. Fade music.
    The brightest star in Gemini is this one, Pollux [point to and show label]. It’s 34 light-years away, and the brightest star known to have an extrasolar planet. The planet is even bigger than Alrai’s—more than twice the mass of Jupiter—and orbits in about 590 days, which is similar to Mars in our solar system. You can see this star from about October (around midnight) through June (just after sunset). Is this a strange planet? Well, Pollux is an orange giant star, evolving into its red giant stage. So yes, you might call this a strange planet with an orange giant sun. Once Pollux is fully evolved into a red giant, it may have grown to size so big that it will engulf this planet!
    VISUAL 11 (still): Sun, Orange Giant, Red Giant size comparison

    Optional: Find Pollux on Uncle Al’s Kepler Star Wheels.

    Fade off the red giant size comparison image.

    DIGITAL EFFECT:  Exoplanets
    Fade on exoplanet markers, and add some diurnal motion for dramatic effect. After a stop, fade off the exoplanet markers.

    DIGITAL EFFECT:  Exoplanets
    Show exoplanets (for full-dome digital systems) and explain that it shows a some of the over 300 planets discovered to date. 

    Habitable Zones & Kepler’s Laws

    We’re especially interested in planets that might be good homes for living things.
    DIGITAL EFFECT: Our Solar System
    Lift off from Earth, and bring it to a top-down view of our Solar System, with the orbit lines of all the planets (out to Neptune) visible. If possible, scale the Sun and the planets sizes up for better viewing to make them visible for the audience. Start annual motion to put the planets in motion.

    VISUAL 12 (optional still): Top-view diagram of Solar System

    DIGITAL EFFECT: Planet Markers
    Show full-dome digital view from above Solar System, with planets labeled/marked & orbits on.

    Why don’t we expect to find life on Jupiter or Mercury? [Jupiter is made of mostly gas, with very high pressures, and we don’t even know if it has a solid surface, though it’s thought to have a rocky core. Mercury is simply too hot—water would vaporize rapidly. It’s also so small, it’s gravity is not strong enough to hold onto an atmosphere.]

    Hot Jupiters are gas giants that are too hot, unlikely to have life. Jupiter’s moon, Europa, is another story altogether. It has liquid water ocean below a crust of ice.

    So what about finding planets more like Earth?

    What are the conditions that make Earth good for life? [Take any answers, but focus towards the idea that Earth is not too hot, not too cold, not too big and not too small.]

    The key is water. And not just any kind of water.

    What would happen to water on Mercury where the temperature is over 600 degrees? [It boils.] What happens to water in the outer parts of the solar system where it’s REALLY cold? [It freezes.]

    Water in the form of ice or steam is not what living things are made of. Life needs LIQUID water. So, like Goldilocks and the Three Bears, we need a planet that’s not too hot, not too cold, but juuuust right.

    So we are really keen on finding a planet has the right size orbit that keeps the planet not too far and not too close to its star. This is sometimes called the goldilocks zone, but it’s more formally called the habitable zone.
    VISUAL 13 (movie): Habitable Zone

    Size is also important.

    Very small planets with low gravity would not be suitable for life? Why do you think that is? [Not enough gravity to hold an atmosphere.]

    And we already talked about why a big planet is not suitable for life: gas giants have crushing atmospheric pressures. So just as with temperature, there is a magic “Goldilocks zone” of size: not too big and not too small, but juuuust right—about Earth-size or thereabouts.
    ...Which brings us back to the NASA Kepler mission. It’s designed to find planets and for each discovered planet, determine its size and distance from its star. It’s main mission is to find Earth-size planets in the habitable zone of stars.

    VISUAL 14 (still): Johannes Kepler

    The following section on Kepler’s Laws may be omitted for most audiences.
    Kepler’s name honors a mathematician and astronomer, Johannes Kepler, who, 400 years ago was an assistant to Tycho Brahe—the greatest observational astronomer of his time. Brahe over decades had made detailed astronomical observations. Kepler used Brahe’s astronomical tables to formulate three laws of planetary motion that, for the first time, could predict the positions of planets with great accuracy.

    DIGITAL EFFECT: Kepler's 1st Law


    Kepler’s First Law

    Do you know what shape orbits of planets have? [Ellipses, or ovals.]

    VISUAL 15 (still): Orbits are ovals graphic

    DIGITAL EFFECT: Top-Down View of Solar System
    Keep showing full-dome digital top-down view of solar system.

    That’s Kepler’s First Law of Planetary Motion—that planets move in elliptical orbits. Most planets have nearly circular orbits, but not perfectly circular.

    What keeps the planets in their orbits? [Gravity.]

    Right. Kepler didn’t know about gravity, but he did notice a pattern to how fast a planet moves at different places in its orbit.

    Kepler’s Second Law

    VISUAL 16 (still): Equal times/equal areas

    He described an imaginary a line drawn from a planet to its star. The area swept by that line when it’s closer to the star looks different from the area swept by the line when the planet’s farther from the star.

    Which area looks larger, the one when the planet is closer or the one when the planet is farther from its star?

    Trick question. Actually, they are exactly the same size. And that’s Kepler’s second law: a planet sweeps out equal areas in equal times. A simpler way to think of it is that a planet moves faster when it is close to the Sun and slower when it is further from the Sun.
    VISUAL 17 (movie): Elliptical orbit

    Music—music of the spheres....
    And what’s causing that to happen—the planet moving faster when it’s closer to the Sun? [Gravity.]

    Remember, Kepler did not know about gravity, so he did not know why his second law works. In fact, no one had an explanation until Isaac Newton came along with his law of universal gravitation some 70 years later.

    Kepler’s Third Law

    Kepler’s third law is the most important one for the NASA Kepler mission. Johannes Kepler was a firm believer that the physical properties of the Universe could be described purely by mathematics. So, looking for more patterns in the data, he discovered the mathematical relationship between distance a planet is from its star and the time it takes to orbit: the square of the orbit time is proportional to the cube of the orbit distance.
    VISUAL 18 (still): Graph of Kepler’s 3rd Law (T2 d3)
    Don’t mention log scales unless someone asks.

    Fade off graph of Kepler's 3rd Law.

    This graph shows Kepler’s 3rd law.
    Optional: Explain the graph.
    The y-axis is planet orbit time and the x-axis is planet distance “Astronomical Units” or AUs for short. You can see on the graph Earth’s orbit time is 1 year and distance is one AU—in fact that’s the definition of an AU: the average distance from the Earth to the Sun. Saturn’s at about 10 AU and takes about 30 Earth years to orbit the Sun.

    Kepler’s 3rd Law lets us calculate the distance of a planet from its star if we can find the time it takes to orbit. And the distance, as you now know, is critical to whether or not the planet is in the habitable zone!


    Transiting Planets


    In lieu of the live demonstration or alternative movies in this section, presenters may wish to use the sequence in the Optional box below.
    Using another very clever technique, we can not only discover extrasolar planets, but determine fairly accurately how big they are and, armed with Kepler’s Third Law, we can find out how far they are from the star.
    If you do not have an orrery with light sensor, and the system for projecting light curve graphs in real time, you may alternatively use the Orrery and Live-Graph movies. However, using the real live orrery/light curve set-up is much more fun….

    VISUAL (alternative movie): Orrery

    Point out light sensor, model star (light) and planets. Explain that the sensor will feed star brightness data to a computer and show us a graph of brightness changes.

    For live presentation, use either hand-crank demonstration orrery (LEGO model or equivalent, shown above) or the “Walking Orrery” (below).

    VISUALS (alternative movies): The orrery in action synchronized with the live light curve graph
    You can show these side by side or one above the other, in lieu of the a full-blown simulation setup.

    On the orrery make sure the light sensor is aimed at the star-bulb. Switch on the video projector and wake up the laptop, to feed data from the light sensor to the projector, to show Brightness vs. Time graph on the dome.

    Caution the audience that you are about to turn on a model star, then turn on the model star, but do not spin it yet.
    This is a light sensor that measures the brightness of the star. We can think of this as a model of the NASA Kepler spacecraft and its light sensing camera. [Optional: It’s also called a photometer because it measures amount of photons of light.]
    Vary the display in an obvious way—by putting your fingers or hand between the sensor and the light.
    Look! That picture shows the brightness of the star! It’s a graph of light brightness—called a light curve. You can even tell how long my hand is blocking the light without even being able to see my hand. Just look at the light curve....
    Optional: Have audience volunteers block the light with their hands.

    Let the graph stabilize so the audience can see the flat line that represents the normal star’s brightness, as detected by our “telescope” sensor. Then point out the Orrery.
    This is a model star with extrasolar planets we are trying to find.
    Run the orrery by having a volunteer holding the panet walk around a volunteer holding the star (for Walking Orrery) or by turning the crank on the orrery so the planet(s) periodically block the light entering the sensor, making a light-curve graph. If using volunteer instruct them to crank gently and steadily. If the volunteer is somewhat erratic, you can comment that it looks like our solar system machinery is “only human.”
    What happens when this extrasolar planet passes between the star and our photometer? [There is a dip in the graph.]

    The extrasolar planet is blocking the light from the star, and our sensor detects it! What a great way to find extrasolar planets! It’s like an eclipse. Astronomers call it a “transit,” which means “going across.” Looking for stars that are having their light blocked as a planet goes across is called the “Transit Method” of finding extrasolar planets.

    One limitation of the Transit Method is that it only works if the extrasolar planet and its star are tipped just the right way.

    What if the extrasolar planet orbited the star at an angle that was not lined up with our sensor? [No transit could be detected.]

    Let’s see what we can tell from this light curve graph.
    Have a volunteer crank the orrery or for the Walking Orrery, have two volunteers: one to hold the star and the other to walk around it with the planet.
    How can you tell from the light curve if a planet is big or small?
    [Big planets make deeper dips in brightness.]

    We can also measure how often light is blocked—that means how much time passes from here to here on the graph [point out the distance between dips on the projected graph]. We saw this before, too! That’s the period.

    How can you tell from the light curve if the planet is close to or far away from its star?
    [Farther out planets make dips that are more widely spaced.]

    If the dips on the light curve graph are close together—then the planet is orbiting the star really fast, and it must be really close to the star. That means it is a hot planet.

    Look how close the dips are in that light curve graph!

    If you have an orrery with only 1 planet (the Portable Star-Planet model or the Walking Orrery), you can still analyze light curves as follows: Have an audience member volunteer turn the crank (or walk around, in the case of the Walking Orrery) but after 15 or 20 seconds, ask them to stop so you can quickly put on (or hand them) a different size planet. Ask them to continue cranking (or walking) at as steady a speed as they can. In this way, you will generate two “half” light curves, side by side. In many ways, this is even easier for people to analyze than the light curve with two planets going simultaneously.

    Point to most closely spaced dips.
    That’s a close, hot planet!
    Point to most widely spaced dips.
    Then the planet would have to be far away from the star, and that means it is a colder planet. Look how far apart the dips are on that light curve graph! That planet is really creeping—must be far from its star. Brrr! That’s a cold planet!

    Since big planets block a lot of light and small planets only block a little bit of light, big planets are easier to find than small planets! Just like with the spectra of star wobbles. Big hot Jupiters are the easiest to find.
    VISUAL 19 (movie): Transit Light Curve


    DIGITAL EFFECT: Transits
    Show a native rendering of Earth passing in front of the Sun.

    To a distant astronomer, here’s what a transit of Earth might look like. Earth passes in front of the Sun, and then one period later—that is, one year, in Earth’s case—you get another transit.
    VISUAL 20 (movie): Optic Path

    In the case of Kepler, we’re looking at distant stars. Planets pass in front of their stars, and then the instruments on Kepler detect that change in brightness.
    VISUAL 19 (movie): Transit Light Curve

    From detection, astronomers generate a light curve, and measure the dimming effect.
    From the small change in brightness, you can figure out the size of the planet.

    If you see a big drop, what does that tell you about the size of the planet? [It must be a big planet.] Right—and a small drop means a small planet.

    Kepler will have to stare long enough to see the planet repeat the transit several times. From the period of the transits and using Kepler’s Laws of planetary motion, you can calculate how far the planet is from its parent star and know if it is in the habitable zone.

    Fade off transit animation.

    VISUAL 21 (still): Kepler spacecraft

    The Kepler instrument uses a light sensor like the one we’ve been using today, except that it’s huge, with nearly 100 million pixels, and it’s in a big telescope to collect lots of light. How many pixels does your digital camera have? 5 megapixels? 8 megapixels? I bet it’s not 100 megapixels, like the Kepler spacecraft camera! And with that sensitivity, Kepler can generate a light curve for individual stars to find planets!

    The transit method of planet finding is second only to the spectroscopic method in terms of numbers of planets discovered so far, but the Kepler Mission could change all that. In February of 2011, the Kepler team released data containing 1,235 planet candidates. The planet candidates are not all confirmed planets, but many of them are very likely real planets.

    Finding an Earth-like Exoplanet

    So if we will be getting all this data from the Kepler mission, how will we know if we do find an Earth-like planet in the habitable zone? Let’s imagine we are the planet finders and have look at some data.
    VISUAL 22 (still): Light Curve Kepler-10b

    Here is light curve data from one of the Kepler stars that has a discovered planet named Kepler-10b. We can determine how big the planet is from how deep the dips in brightness are.

    On the Kepler 10b graph, how deep is the dip, in % brightness drop? [Almost .02%.]
    VISUAL 23a (still): Planet Size Lookup Chart

    Look at the Brightness Change vs. Planet Size Lookup Chart.

    How big is a planet with .02% brightness change?
    [About 1.4 times Earth size]

    You can also determine how far the planet is from it’s star by measuring how widely-spaced the brightness drops are, to find the planet’s orbit time (period).

    On the Kepler 10b graph, what is the orbit time? [About 0.8 days.]
    VISUAL 23b (still): Orbit Distance Lookup Chart

    Now look on the Orbit Time vs Orbit Distance Lookup Chart.

    How far out is a planet with a 0.8 day period?
    [Less than 0.02 AU or about 6 times the Earth-Moon distance.]

    Is that an Earth size planet? [Close.] Is it in the habitable zone? [No.]

    Let’s look at Light Curve for the star Kepler-11.
    Fade off Kepler-10.

    VISUALS 22 (stills): Light Curves for Kepler 11a, b, c, d, e, f, shown in 3 graphs, 1 pair in each graph
    Fade on the light curve for the Kepler-11. The six planets are separated onto three separate light curves, with two of the Kepler-11 planets on each—e.g., Kepler-11b and Kepler-11c on one graph, Kepler-11d and Kepler-11e on a separate graph.

    Here you should be able to see 2 planets in each of the light curve graphs. Let’s pick one planet to focus on, say Kepler-11c.

    How deep is the dip, in % brightness drop for Kepler-11c?
    [0.1 or one tenth of 1%]
    From the Planet Size Lookup Chart, how big is a planet with 0.1% brightness change? [About 3.2 times Earth’s size]

    What is the Orbit Time for Kepler-11c?
      [About 13 days.]

    Now look on the Orbit Distance Lookup Chart.

    How far out is a planet with a 13 day period?  [About 0.06 AU or about 1/16 the distance from Earth to the Sun.]

    Is that an Earth size planet? Is it in the habitable zone? [No. It’s closer to the size of Uranus and way too close to the Sun.]
    Optional: Pick one or more other planets of Kepler-11 and do similar analyses to determine planet size and size of orbit. 

    Fade off planet size/ orbit distance tables.

    Fade off Kepler-11 light curves.

    Optional Technique (takes longer):

    After analyzing light curve for Kepler-10b as a whole group, have “small groups” analyze the rest of the light curves, Kepler-11a through f. Give out the Strange Planets take-home handout Side 1 and Side 2 to each group to find Size and Distance for each of the exoplanets from the light curves. Remind them they are looking for an Earth-size planet that is in the habitable zone of its star. If a group finishes it’s assigned star, they can go ahead and pick another star to work on.
    Turn on “planet-finding music.”

    After all have found results on their assigned star, have a discussion with the group as a whole about whether any of the planet(s) are Earth-like and habitable, and how they know that.

    Optional: Show combined light curve for Kepler-11a, b, c, d, e, f, in color coded version and/or simple black and white with no labels. This shows an inkling of complexity of what the Kepler light curve analysts are dealing with.

    VISUAL 22 (still): Light Curve for Kepler 11a, b, c, d, e, f (continued)
    Fade on the light curve for the Kepler-11. All six planets are shown on one light curve.

    VISUAL 22 (still): Light Curve for Kepler 11a, b, c, d, e, f (continued)
    Fade on the light curve for the Kepler-11, with no color. All six planets are shown on one light curve.

    Fade off Kepler-11.

    VISUALS 24a and 24b (optional stills): Artist’s conception of Earth-size planet.

    What does it look like—this potentially habitable planet we found? What is its surface like? Does it actually have life? If it does, what is that life like? 

    Isn’t it amazing that just by studying a light curve graph of a star’s brightness over time, we can learn such a tremendous amount? We can find out a planet’s size, how long its year is, how far it is from its star, and even the prospects for it supporting life!

    It is possible to create and to load files to simulate the Kepler exoplanetary systems. These digital effects can be placeholders to add your own effects.



    DIGITAL EFFECT: Exoplanets
    Turn on all exoplanet markers.

    We are finding new extrasolar planets all the time. But the goal is to find these habitable, Earth-like planets.
    DIGITAL EFFECT: Conclusion
    Ensure that Cygnus and the Kepler field of view target area are visible. Scale up the Kepler spacecraft image and rotate it to “point” toward the target area. 

    VISUAL 25 (still): Kepler’s target area
    Three versions of this are available. One has the star field with the CCD pattern superimposed. Another is just the CCD pattern that you can position over the actual stars in your planetarium—especially suitable for digital star projectors. The third is first light image from the Kepler spacecraft, produced in April 2009.

    The NASA Kepler mission is specifically designed to survey our region of the Milky Way galaxy, to discover hundreds of planets. Kepler is staring at a this section of the sky, that you see here near the constellation Cygnus (the Swan), staring for three and a half years, never blinking, and surveying about 150,000 stars simultaneously.
    VISUAL 26 (movie): Kepler’s orbit around the Sun

    Kepler is following (trail) Earth in its orbit around the Sun. Every three months, Kepler executes a 90° roll to keep its solar panels pointed towards the Sun and at the same time keep its exquisitely sensitive photometer (light meter) aimed at those 150,000 stars.
    VISUAL 27 (movie): Diversity of Life

    DIGITAL EFFECT: Exoplanets 
    Fade off the Kepler spacecraft, Cygnus, and field of view target graphics, and fade on the exoplanet markers one final time.
    The ultimate goal is not just to find planets, or even “hot Earths,” but to find Earth-sized planets that are not too hot, and not too cold, but just right for life to develop.

    If we do find Earth-sized planets, it will be a tremendous discovery. Equally exciting is that the Kepler mission is designed to settle the age old question of whether planets like ours are common or not. Even if we do not find an Earth-sized planet in the habitable zone of a star, that would also really significant, because that would tell us that planets like ours are quite rare, and our home planet all that much more precious and worth preserving. And underlying everything, Kepler results have implications in answering questions about the possibility of life existing elsewhere in our galaxy. Are intelligent beings common or rare in the Universe? Kepler mission is a serious first step to get real data that may eventually lead to an answer that question!
    VISUAL 28 (still): Learn More
    Fade on a text graphic with the URLs for the Kepler Mission website and the Planet Hunters website.

    You can find out a lot more about this quest from the Kepler website, You can also join in the search at

    Thank you for coming to our planetarium today!
    DIGITAL EFFECT: Return Home
    Fade off all the planet orbit lines. If necessary,
    scale all the planets and the Sun to their default
    sizes, and approach Earth. Crossfade the scenes to land on Earth at "today, noon" and "local latitude, local longitude".

    VISUAL 29 (still): Credits


    About Exoplanets

    California & Carnegie Planet Search
    The Extrasolar Planets Encyclopedia website at
    Kepler Mission website
    Kepler Star Wheel:
    Make a LEGO® Orrery:
    PlanetQuest Website
    Wikipedia, the free encyclopedia— “Extrasolar Planet” Wikimedia Foundation.
    Top 10 Most Intriguing Extrasolar Planets

    Worldwide Web Connections

    and updated information may be found at:

    The Kepler team displays the variations in brightness in a graph of brightness versus time, known as a light curve. One day, one of the Kepler scientists looked at the light curve of a star identified in the Kepler Input Catalog (KIC) as KIC12253350 and thought that a section of it looked like a heart. There was some moderate debate among some of the Kepler team as to what kind of variable star KIC12253350 must be, but no conclusive categorization has been agreed on. This T-shirt was produced for the January 2011 American Astronomical Society meeting in Seattle and for Valentine’s Day 2011. Another Keper T-shirt has also been made (Got Planets?)—see

    Black, back

    Black, front

    White, back

    White, front


    Production of Strange Planets was a joint effort of the Pacific Science Center planetarium (Alice Enevoldsen and Steve White) and the Lawrence Hall of Science Planetarium.
    Funding for Strange Planets was provided by two sources: Thanks to Edna DeVore of SETI Institute for advice and for arranging for the funding of free planetarium show kits for the release of this program in the International Year of Astronomy (2009).

    The following Lawrence Hall of Science staff ran the pilot tests in summers of 2008and 2009: Simona Balan, Malavika Lobo, Amelia Marshall, Margaret Nguyen, Katherine Koller, Alexandra Race, Sindhu Kubendran. Margaret Nguyen, Alexandra Race, and Sindhu Kubendran were actors for video sequences. Formative evaluation concepts were devised and implemented by Lawrence Hall of Science Research, Evaluation, and Assessment (REA) team member, Scott Randol as well as Dawn Robles of Inverness Research Associates. Sallie Lin of REA served as an observer for formative evaluation in the Lawrence Hall of Science pilot tests of 2008. Fiona Potter and Lucy Liu assisted in modeling the Walking Orrery that was added in 2011.

    We are especially thankful to the following planetariums for field testing the show and providing feedback for the final version:

    Updated 2/20/2015