Planetarium Activities For Successful Shows™
by Michael Askins, John Erickson, Alan J. Friedman,
Alan D. Gould, and JohnMichael Seltzer
revised by Toshi Komatsu
The program begins by students observing and pointing out stars of different colors. They then see a demonstration of how the color of a star is related to its temperature. The class pretends to go to a planet orbiting a red star and observes how the colors of objects appear different, depending upon what color of light is shining on them.
Next, the students use light filters to discover how different color filters can allow astronomers to see particular details in astronomical objects. Then, they use diffraction gratings to analyze the colors that comprise light and determine what stars are made of by examining emission spectra. Finally, the students find out some of the ways that astronomers detect invisible colors of light that are beyond the ordinary visible rainbow colors of light.
Understanding color absorption and reflection is not common sense and takes time. We recommend that you prepare yourself as well as your students with background activities found in the Great Explorations in Math and Science (GEMS) guide, Color Analyzers, available from the Discovery Corner Store, The Lawrence Hall of Science, University of California, Berkeley, CA 94720-5200. http://www.lhsgems.org/GEM226.html
As with all of our planetarium programs, we would be very grateful to hear about how you used this program, what modifications you made, what worked well, and what did not work well.
In this planetarium program, the students will be able to:
We do not 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 planetarium controls, demonstrations, 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 images 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.
DIGITAL EFFECT: Title
Description of digital effect
Boxes like the one to the right are for presenters, and signify when to use a particular digital effect in your planetarium.
DIGITAL EFFECT: Setup
Load all media for the program, including images, video clips, and plug-ins. Set up the sky for the beginning of the program. Use April 1, 2008, as the start date, chosen because red stars like Betelgeuse, Aldebaran, and Arcturus are visible in the sky.
Entrance music on while people come in. Then, fade out music.
Greetings! My name is _______ and I want to welcome you to today’s planetarium program, "Colors from Space." This evening, when we look at the stars, we may want to consider them from a different perspective: how much can we learn about the stars from their constant twinkling lights?
All we have ever received from stars is their light, and it is up to us to discover their secrets and the nature of the universe by unraveling the information contained in that light.
One important feature of light is color.
What color (or colors) would you say the stars are? [Accept any answers: white, yellow, grey, silver, clear, etc.]
Although most stars may look white or yellow to us, there are quite a few stars that glow with a different color; some red or reddish, some bluish, but it takes a certain level of brightness for the eye to recognize color. Next time you are outside on a starry night, look carefully and see how many differently colored stars you can find.
In the planetarium, we can speed up time. As the day wears on and the sun goes down, the sky will get darker and, if it’s a clear night, the stars will come out.
Slowly fade out lights.
DIGITAL EFFECT: Sunset
Go to a few hours past sunset, approximately 9:30 p.m. local time.
Fade in music and wait to allow eyes to adjust and let people look at the stars; then fade out music.
Now, let’s find some stars that have a different color than usual.
Can you find any stars that have some unusual color, different from white, yellow, silver?
If you would like to point it out to the rest of us, raise your hand so that I can give you a light pointer.
Demonstrate pointer. Have several volunteers point out stars of different colors.
DIGITAL EFFECT (optional): Boötes
Display the outline for Orion, as a constellation with a distinctive colored star (i.e., Betelgeuse). You may do the same for Aldebaran in Taurus and Arcturus in Boötes, toggling them on and off.
For each volunteer, ask…
What color does that star seem to you?
Yes, there are stars of many different colors.
Why do you think the stars shine with different colors? [Accept a few answers.]
Most of the stars we see are big balls of hot, glowing gas. But all fires are not the same temperature and similarly, not all stars are the same temperature. For that reason they are different colors.
Which stars do you think are hotter: the yellow or the red stars? Raise your hand if you think the yellow stars are hotter…raise your hand if you think the red stars are hotter…
Let’s do an experiment to find out: Here I have a regular white light bulb which gives off light from a hot metal wire. I can regulate its temperature.
Turn on white bulb in the center and vary brightness to demonstrate. Make sure that everyone can see the light bulb directly.
VISUAL (alternative movie): Star Temperature
Alternatively, use the "incandescent" movie. Fade on and immediately play a short video clip of an incandescent tubular bulb dimming, as a demonstration of color being a function of temperature. May be used instead of a live demonstration.
You may need to move a little so that you can see the wire inside the light bulb. Right now, it is the hottest I can make it.
What color is it? [White.]
Start dimming slowly.
I’ll cool it off a little.
What color is it now? [Yellow.]…and I cool it off more… [Orange.]…and just when it’s about to die out… [Red, then black.]
Start making it brighter again slowly.
If we slowly make it hotter again, what colors does it get? [Red…orange…yellow…white.] Of all these colors, what color are the hottest stars? [White.] And the coolest? [Red.] Which stars are hotter than red but cooler than white? [Orange and yellow.]
Fade off the "incandescent" movie.
There are stars that are even hotter than the white stars. If I could make the light bulb hotter it would turn bluish
Have you ever seen a blue fire? [On a gas stove, an oxyacetylene (welder’s) torch.]
A gas stove’s flame is blue for a chemical reason, but a welder’s torch physically glows blue, and is very, very hot.
On the other hand, have you seen the dying cinders in a fireplace? [They look very red.]
Similarly with the stars, the blue stars are very hot and the red stars are the coolest, even though they’re still very hot!
Stars, like all fires, also cool off with time.
What will happen to the color of a blue star as it cools off? [It will turn from blue to bluish-white, to white, to yellow, to orange, to red, and finally to black.]
What color is the closest star to us? [Yellow.] What’s the name of that star? [The Sun.] The Sun is an average yellow star. Do you think the Sun will always be yellow? [No. It will cool off and become orange, then red.]
Billions of years from now, our Sun will become a red star and things might look very different on Earth. Let’s take a look at what things might look like when that happens.
DIGITAL EFFECT: Red Light
Fill the dome with red light to flood the planetarium, all other lights out.
Alternatively, if your dome has its own red-green-blue lighting system (e.g., cove lighting), you may use that instead of the red light effect.
Look at your clothes. Notice what the colors look like now. If you are wearing red notice if it looks bright or dark.
Who is wearing something red?
Ask a volunteer wearing something red to stand so everyone can see the red clothing.
Who is wearing something blue?
Ask a volunteer wearing something blue to stand so everyone can see the blue clothing.
I’ll ask my volunteers to stand up to display their red and blue clothes so we can compare them.
Which one looks brighter? [The red.] What colors look bright under a red light? [Red, white, and other light colors like yellow and pink.]
Now, let’s transport ourselves to a place near a blue star.
Are blue stars hotter or cooler than red stars? [Hotter.]
Please fasten your seatbelt. We will be using "warp drive with warp factor 100" leaving the red star to go to a planet orbiting around a blue star!
DIGITAL EFFECT: Blue Light
Red light off; Fill entire dome with blue light.
Here we are on a planet revolving around a blue star. What’s different now? Notice the colors around you again.
Which colors look brighter? [Blue and white.]
I’ll ask my volunteers to stand again so we can compare their clothes under this new light.
Which one looks brighter? [The blue.]
It seems that blues and whites and perhaps greens look bright under a blue light; all other colors look dark.
Let’s go back and forth between the red and the blue stars and watch what happens to our volunteers’ clothes.
DIGITAL EFFECT: Alternate Red/Blue Light
Alternate red and blue lights a few times and finish, leaving red lights on.
Ask volunteers to be seated.
To understand the effects we just saw, we need to trace the path of light. All the light in this room is coming from this red light.
Where does the light go next? [Upwards to the top of the dome.]
When the light hits the top of the dome it bounces off in all directions. We call this bouncing-off reflecting. So, the light from the red bulb bounces off the dome and reflects all over, hitting other things and reflecting off of them. But when light hits an object, it doesn’t always bounce off or reflect—sometimes it is absorbed. Just like a sponge can absorb water, things can absorb light. When an object reflects light, some of that reflected light comes into our eye and we see the object bright. When an object absorbs light, the light doesn’t reach our eye and it looks dark. Look at the red clothing in this light.
Does red light reflect from it into our eyes, or does the red clothing absorb the red light? [Reflects.]
Look at blue clothing.
Does the red light reflect from it into our eye or does the blue clothing absorb the red light? [Absorbs.]
Now, let’s do the same experiment in blue light.
DIGITAL EFFECT: Blue Light
Turn off red; turn on blue.
Does the blue light reflect off of red objects or is it absorbed? [Absorbed.] And does the blue light reflect off of blue objects or is it absorbed? [Reflects.]
This is why things appear to be colored; blue objects reflect mostly blue light and absorb most other colors, while red objects reflect mostly red light absorbing most other colors. Objects with colors like white and yellow reflect most colors of light.
DIGITAL EFFECT: Red Light
Turn off blue; turn on red.
Now, let’s go back to a red star and examine a piece of cloth (or color pattern on paper). Space travelers call it "the mystery cloth" because they have a hard time agreeing on the colors they see on it.
Make sure only the red light is on. While you talk, start unrolling the multicolored cloth or handing out paper color patterns so that everyone will have it in front of them. With rolled-up cloth, once you start, let the audience continue unrolling.
Will someone please describe the pattern on this cloth for us? [Stripes of the same width; colors.] Does everyone agree with that description? [Accept a few opinions.]
Perhaps we can agree that there is a bright stripe that reflects red light (or looks bright under red light) and a dark stripe or two that absorbs it (or looks dark under red light).
Let’s take the cloth to a different star, a green star perhaps, to see if we can get some more information about the colors of this cloth. Please fasten your safety belts again.
DIGITAL EFFECT: Green Light
Red lights off; Fill the entire dome with green light.
Expect gasps of astonishment from your students.
Wow! What happened!!? Could this be the same piece of cloth?
Would someone please describe this new pattern for us? [There’s a new thin zig-zag line, so there are three stripes of different widths. Colors?] Does everyone agree with this new description? [Listen again to a few opinions.]
We want to discover the true colors of each of those stripes, and to do this we can use what we learned when we looked at our clothes under different color lights.
Does that zig-zag look bright or dark? [Dark.]
That is because it must be absorbing the green light.
Is it possible that the zig-zag could be green? [No. If so, it would look bright.]
What about the background stripe that the zig-zag is on, does it look bright or dark? [Bright.]
It looks bright because it is reflecting the green light.
Is it possible that the background could be green? [Yes.] Could it be another color? [White.]
Now keep track of that zig-zag by putting your finger on it while we return to the red star to see what happens.
DIGITAL EFFECT: Red Light
Turn green light off; red light on.
The zig-zag disappeared! Where did it go? I told you to keep track of it!
Now, does the area where the zig-zag is supposed to be look bright or dark? [Bright.]
The zig-zag and its background are two different colors but they are reflecting red light equally.
Is it possible the zig-zag could be red? [Yes.]
Now its background looks bright, too.
Could it be red, also? [No.]
It looks bright with both red and green, so it probably is white, yellow, or some other color that reflects both red and green. Now, put your finger on the dark stripe.
Could this be red? [No, because it absorbs red light.]
Let’s go to a green star.
DIGITAL EFFECT: Green Light
Red light off; Fill the entire dome with green light.
The stripe looks bright.
What color do you think it could be? [Green; or maybe, blue.]
If it is blue it should look brighter near a blue star: let’s see.
DIGITAL EFFECT: Blue Light
Green light off; Fill the entire dome with blue light.
It looks darker, therefore it’s not blue, it’s probably green. So far we have guessed a wide green stripe, and a red zig-zag on a white or yellow background.
What color light do you think we could shine on the cloth to see its real colors?
If they say: red, blue, green, respond: "We already looked at it with those colors." When they say any other color: "I only have red, blue and green." When they suggest white or a combination…
Let’s see what happens when we combine colors. Look at the ceiling as I mix the colors: We have blue light, now we add green.
DIGITAL EFFECT: Green/Blue Light
Fill the entire dome with a mix of green and blue light (i.e., cyan), as a color combination.
We get aqua (or turquoise, cyan, or plain blue-green). Let’s add red to blue.
DIGITAL EFFECT: Red/Blue Light
Fill the entire dome with a mix of red and blue light (i.e., magenta), as a color combination.
We get pink (or purple, or magenta). Let’s add green to red.
DIGITAL EFFECT: Red/Green Light
Fill the entire dome with a mix of red and green light (i.e., yellow), as a color combination.
We get yellow!
This is usually a surprise for most people.
And finally let’s have red, green and blue together
DIGITAL EFFECT: Red/Green/Blue Light
Fill the entire dome with white light, to demonstrate "white light" as a combination of red, green, and blue combined.
We get nearly WHITE!! White light is made from all colors mixed together. Look at your clothes now.
Do they look their normal color again? [Yes.]
Now we can see the "true" colors of the cloth and we find that we were correct in our guesses.
Please roll-up the cloth that is not-so-mysterious anymore.
Collect cloth once it is rolled up.
DIGITAL EFFECT: Red Light
Fill the entire dome with of red light.
In summary, we can say that an object looks brightest when illuminated by light of the same or nearly the same color (because the object reflects the light), and looks dark when illuminated by a light of very different color (because the object absorbs the light). Pale colors and white look bright in any color light, and dark colors like black, or brown, look dark in any color light. The red zig-zag and its pale background looked equally bright in the red light. In fact we could not tell they were different and that’s what made the zig-zag disappear. On the other hand, in blue or green light the red became very dark, while the pale background remained bright. This is because light striking an object is either reflected into our eyes, or absorbed. Objects reflect mostly the color light that they appear to be, and absorb all other colors.
We just looked at light reflected from objects like cloth. We will now look at how light goes through certain kinds of windows. I am handing out some devices that we call "color analyzers." When you get yours, look for four windows—each of them labelled with the letters A, B, C, and D.
VISUAL (alternative movie): Filters
If your presentation is not using physical color analyzers with your audience, show the "filters" movie. Fade on and immediately play a short video clip of the filters activity. Pause the movie on each color section to ask the questions. May be used instead of a live demonstration.
Hand out the color analyzers, keeping one for yourself. Make sure only the red light is on.
I’d like you to hold your color analyzer up and look at the ceiling through the windows.
Demonstrate with yours.
Which window looks brightest? [D.] Which is second brightest? [A.]
Notice windows B and C look black or very dark. Each window has a different color of plastic in it. Can you tell what color each window is?
What color is window A? . . . B? . . . C?
As we go through different colors of light we will display images of color analyzers against a red, green, blue, and white background, positioned 45° from the horizon, and spaced 90° from each other. Individual images may be toggled on/off. May be used either to summarize live use of filters, or to summarize the video (if used).
VISUAL 1a: Analyzer Red Light
Fade on still image of color analyzer against a red background, positioned 45° from the horizon.
Let’s go to a different star, say a green star.
DIGITAL EFFECT: Green Light
Switch off red, switch on green. If using the movie, keep a still image of the color analyzer in red light on.
Now, which window looks brightest? [D.] And the second brightest? [Window B, but window C is also bright.]
Also, notice that window A looks dark.
Do you want to revise your guess as to what colors the windows are?
VISUAL 1b: Analyzer Green Light
Fade on still image of color analyzer against a green background, positioned 45° from the horizon.
Let’s go to a blue star.
DIGITAL EFFECT: Blue Light
Switch off green, turn blue on. If using movie, keep still image of color analyzer in green in separate place on dome.
Again, which window looks brightest? [D.]
And the second brightest? [Window C, and now window B is bright but dimmer.]
Notice again that window A looks dark.
Now, do you think you can guess what colors windows A, B, C and D are?
VISUAL 1c: Analyzer Blue Light
Fade on still image of color analyzer against a blue background, positioned 45° from the horizon.
DIGITAL EFFECT: Red Light
Turn off blue; turn on red. If using movie, refer to red and green still images on the dome. You can use the blue still image, but the movie goes directly to the view with white light after blue, so make sure to pause the movie for discussion about what the filter colors are.
What color do you think window A is? [Red.] And window B? [Green.]
DIGITAL EFFECT: Green Light
Turn off red; turn on green.
And window C? [Blue.]
DIGITAL EFFECT: Blue Light
Turn off green; turn on blue.
And window D? [Clear, transparent.]
DIGITAL EFFECT: White Light
Turn on red, green and blue.
VISUAL 1d: Analyzer White Light
Fade on still image of color analyzer against a white background, positioned 45° from the horizon.
The plastic in the windows we have been looking through are called filters. Filters can also be made of other materials such as glass.
A red filter lets red light through and absorbs light of other colors. A blue filter lets blue light through and absorbs red and all other colors. A green filter lets through only green light, etc. In summary, a filter lets through light of one color (its own) but absorbs the rest.
The rules for filters are very similar to the rules for the reflected light from other objects; filters let light of one color pass through to our eyes while colored objects reflect light of their color to our eyes.
Astronomers, engineers and scientists use filters in various ways. For instance, here’s a picture of Mars taken by the Viking spacecraft.
This picture was taken with a black and white camera and a filter.
What color filter was it? [Red.]
Then, the Viking took a picture of the same scene with a blue filter.
DIGITAL EFFECT: Mars Blue Filter
"Push" the red Mars image along the horizon to a new location, and make a blue-filtered image appear at the original location of the red image. Note: The exact positions along the horizon may be adjusted, but the timing of the "push" will also have to be adjusted.
VISUAL 2b (still): Mars with Blue Filter
The camera viewed the same scene also with an amber filter. The Viking spacecraft sent all the information to Earth where NASA scientists used computers to put the pictures together to get a color picture of Mars taken with a black and white camera!
DIGITAL EFFECT: Mars Color
"Push" the blue Mars image over to the new location of the red image, and then "composite" the two together to form a color image. Note: Again, the exact positions along the horizon may be adjusted as the user sees fit for their own theater, but the timing of the "push" will also have to be adjusted.
VISUAL 2c (still): Color Picture of Mars
A color TV set works in a similar way. It receives pictures of only red, green and blue and your set puts it together. The U.S. flag you see on the spaceship was used to adjust the colors to the right mix, by comparing it with an identical flag on Earth.
Let me show you how astronomers can use filters to learn more about the things they see in space. Sometimes they can see much more contrast, and finer detail, by selecting only one color
Fade off the Mars image.
VISUAL 3a (still): Jupiter through Blue Filter
Show a black-and-white blue-filtered image of Jupiter. Note the dark shading of the Great Red Spot.
Do you recognize this planet? [Jupiter.]
It’s easy to tell Jupiter with its Great Red Spot. But wait! Where’s the red spot? This picture was taken with a filter.
Can you guess what color filter? [It was red.]
All areas of Jupiter reflecting red light look bright in this image. A blue filter makes some features stand out, easier to see as you can see in this same picture taken with a blue filter.
VISUAL 3b (still): Jupiter through Red Filter
Shows a black-and-white red-filtered image of Jupiter. Note the bright shading of the Great Red Spot.
Fade off the Jupiter images.
Notice the red spot appeared, other features now look dark and stand out. So, different filters can make different details stand out.
Here’s a series of pictures of The Ring Nebula in Lyra, a gigantic cloud of dust and gas in space. Ring shaped nebulae (planetary nebulae) are the remains of very old stars. These pictures were taken with different filters, each of them showing different details.
VISUAL 4a (still): Ring Nebula through Red Filter
Show the Ring Nebula in a sequence of still images, starting with a red-filtered image.
VISUAL 4b (still): Ring Nebula through Yellow Filter
Show a yellow-filtered image of the Ring Nebula, 180° from the red-filtered image.
VISUAL 4c (still): Ring Nebula through Green Filter
Show a green-filtered image of the Ring Nebula, 90° from the red- and yellow-filtered images.
VISUAL 4d (still): Ring Nebula through Blue Filter
Show a blue-filtered image of the Ring Nebula, 180° from the green-filtered image.
Now the composite picture...
DIGITAL EFFECT: Ring Nebula Color
Move all four color-filtered images to a single location, and "composite" them into a single color image.
VISUAL 4e (still): Composite Color Picture
...the Ring Nebula in full color.
Fade off the Ring Nebula image.
VISUAL 5 (movies): Multiple Sun Views
The Multiple Sun Views set of videos displays 10 simultaneous videos of the Sun. Each individual video is a view using a different wavelength, but all were taken at the exact same time on the Sun.
Here's another example of using filters looking at the Sun. Each individual video is a view of the Sun using a different filter, focusing on a particular wavelength of light. All ten of these video clips cover the same 17-hour time span. Notice how different the Sun looks in each view—depending on which filter you use, some features are enhanced, while others may be invisible. Astronomers use filters so they can get a more complete picture of objects or events, and each filter view adds one more piece to the whole.
Fade off Multiple Sun Views
Using filters is one way of separating light into its individual colors. Another way of separating light into its component colors is using a "diffraction grating." Window D in your color analyzer is not just a clear window, it is a piece of plastic with thousands of parallel grooves called a diffraction grating. When light goes through the grooves, it splits into different parts, so we can see what makes up the original light. Look directly at this light in the center through Window D, holding it very close to your eye.
Gradually turn on the variable white light in the center. Demonstrate how to look through the diffraction grating. Then, check that everyone’s face is directly illuminated by the light from the bulb.
VISUAL (alternative movie): Spectra
Alternatively, fade on and immediately play a video clip of looking at spectra of an incandescent bulb. Pause and fade off the video immediately after the incandescent spectrum. Allow time for discussion if needed. The remainder of the video looks at spectra from various elements, which is used in the next section of the script, "What Stars Are Made Of." Fade on and play the video with modular sections as needed in the next section of the script. May be used instead of a live demonstration.
What do you see? [A straight rainbow.]
VISUAL 6 (still): Incandescent Spectrum
To be used in conjunction with the live demonstration of viewing spectra. Fade on a still of the spectrum of an incandescent light.
Besides the white light in the center you can see rainbows when you look to the left and right of the bulb. Rotate your color analyzers until the rainbows appear to the sides.
Let’s name all the colors we can see through the diffraction grating starting from the one furthest from the light. [Red, orange, yellow, green, blue and purple or violet; have the whole class say the colors.]
Those are the colors that make up this white light. The diffraction grating allows us to see that white light is a combination of many colors: red, orange, yellow, green, blue and violet. But these are just the colors we can see. There are lots of other colors we cannot see; for instance, there is one before the red, called "infrared," and there is one after the violet called "ultraviolet." The areas before the red and after the violet look dark to us even though the invisible colors are there.
Astronomers use diffraction gratings to discover what stars and other glowing objects are made of. They do it by analyzing (or breaking apart) the light that comes from a star. Some stars give off light like this.
Put the hydrogen tube on its power supply, turn it on and turn off the white light. Make sure that everyone has a chance to see the hydrogen light. Caution: POWER supply is high voltage!
Alternatively, use the "spectra" movie, using the pause function to stop on various spectra for discussion as needed.
Look at this light through your diffraction grating.
Can you see the whole rainbow? [No, only 3 lines: red, green-blue and purple.]
VISUAL 6b (still): Hydrogen Spectrum
To be used in conjunction with the live demonstration of viewing spectra. Fade on a still of the spectrum of hydrogen light around the zenith.
Only a gas called hydrogen gives off this combination of colors when it gets very hot. A set of colored lines like these is called an "emission spectrum." So, when astronomers find this particular set of colors in the light of a star, they know that star has hydrogen in it. Most stars in the universe are made mostly of hydrogen. I would like you to remember this set of colors or spectrum, for two reasons: one, to compare with the spectrums (or spectra) from other gases that I am going to show you in a moment, and two, to be able to identify a mystery gas.
Display hydrogen again for a few more seconds, then replace the hydrogen tube with the helium tube and display it in similar way.
Sometimes the light from stars looks like this.
What colors do you see now? [Red, yellow, green, purple.]
VISUAL 6c (still): Helium Spectrum
To be used in conjunction with the live demonstration of viewing spectra. Fade on a still of the spectrum of helium light sequentially around the zenith.
Those are the components of the light from helium. Many stars have helium in them. The hydrogen that "burns" in the stars changes into helium. Remember this spectrum, too.
Replace the helium with the neon tube and display it in a similar way.
VISUAL 6d (still): Neon Spectrum
To be used in conjunction with the live demonstration of viewing spectra. Fade on a still of the spectrum of neon light sequentially around the zenith.
Older stars have a gas that glows like this. This is neon.
What colors do you see through your diffraction grating? [Red, orange, and yellow lines…and a green line.]
Using diffraction gratings scientists can decode the information that comes in the light from stars and know what they’re made of. Also, by looking at how much of each element a star has, scientists can determine the approximate age of that star—in millions or billions of years.
You can show other gases if you wish.
VISUAL 6e (still): Mercury Spectrum
To be used in conjunction with the live demonstration of viewing spectra. Fade on a still of the spectrum of mercury light sequentially around the zenith.
VISUAL 6f (still): Spectra
Turn on an image comparing the full emission spectra of various elements (including iron).
Then pick one "mystery tube," put it on the power supply, and display it. In the following paragraph, the instructor uses water vapor as the mystery gas.
VISUAL 6g (still): Mystery Spectrum
To be used in conjunction with the live demonstration of viewing spectra. Fade on a still of the spectrum of mystery light sequentially around the zenith.
And here’s the mystery gas! If you were an astronomer trying to identify the contents of a glowing gas like this, you would compare its spectrum with the spectra of gases you already know.
Is this spectrum similar to a spectrum you have already seen? [Yes, similar to hydrogen.]
The gas in this tube is made mostly of hydrogen. The other component is oxygen.
What is made with two parts of hydrogen and one of oxygen? [Water.]
The gas in this tube is water vapor, its spectrum is very similar to hydrogen’s.
Turn off power supply.
When we were looking at the spectrum of white light (the rainbow) we noticed that we cannot see any colors beyond violet or red, but there are actually colors there. Special instruments and special photographic film can detect them. Besides ultraviolet and infrared there are many, many other colors of light. Maybe you have heard of "radio waves," "X-rays," and "gamma rays." All those are invisible colors. Astronomers have developed telescopes that can see in all of these colors, and we are learning much more about the universe this way. Some animals can see these invisible colors too, and beings on other planets might have eyes that could see colors that are invisible to us. Let’s look at some pictures that relate to invisible colors:
DIGITAL EFFECT: Invisible Colors
Cycle through image sets for colors invisible to the human eye.
Visuals 7–21 are arranged to illustrate the "invisible colors," first from UV to X-ray, then from IR to Radio. Format for each "color" is:
VISUAL 7 (still): Ultraviolet——Suntan
Show a woman putting on sunscreen as a familiar example of UV rays.
UV rays cause suntans and sunburns. Here we see a person sunbathing, getting a tan. The ultraviolet light that comes from the Sun is responsible for giving us tans. The atmosphere, in particular the ozone in the atmosphere, filters out most of the ultraviolet light from the Sun. Visible light doesn’t go through clouds very well, but ultraviolet can go through clouds. That’s why we can still get sunburned on a cloudy day—we use sunscreen to filter out ultraviolet light before it reaches our skin.
VISUAL 8 (still): UV SDO
Show an artist rendition of the Solar Dynamics Observatory (SDO) spacecraft.
Because the atmosphere filters out a lot of ultraviolet rays, in order to have a clearer view of space in ultraviolet light we need to have ultraviolet observatories up in space, above the atmosphere. This is the Solar Dynamics Observatory (SDO), and it has an ultraviolet instrument it uses to study the Sun.
Here’s a picture of the Sun in ultraviolet light. Remember, we cannot see ultraviolet with our eyes. This image is processed by a computer using familiar colors to indicate different shades of ultraviolet.
You may have seen a picture like this before.
What is it? [An X-ray.]
The X-ray is another invisible color and it can go through some things that visible light cannot.
Can X-rays go through air and through flesh? [Yes.]
That’s why the flesh of the hand doesn’t show. But bones can filter out X-rays better and they leave their "shadow" on the X-ray-sensitive plate.
There are many sources of X-rays in the universe but they are hard to "see" through the atmosphere. The Nuclear Spectroscopic Telescope Array is the first orbiting telescopes to focus light in the high energy X-ray range. This allows us to study various phenomena, such as the remnants of exploded stars and black holes.
VISUAL 12 (still): Cassiopeia A
Show an X-Ray view of supernova remnant Cassiopeia A.
Fade off all X-Ray images.
This color-coded X-ray image shows the supernova remnant Cassiopeia A, located 11,000 light-years away. The blue portion indicates high energy X-ray light. The outer blue ring is where the shock wave from the supernova blast is slamming into surrounding material, whipping particles up to within a fraction of a percent of the speed of light. Observations like this help add one more piece of the puzzle to teach astronomers how these particles are accelerated to such high energies. This is an example of an object in space that gives off very little visible light, but a lot of X-rays. Those would be invisible to our eyes, but are detectable with instruments to tell a larger story.
VISUAL 13 (still): Electric Heater
Show a hand being warmed by a space heater to illustrate infrared radiation.
In many homes there are devices that produce a lot of infrared rays, plus some visible red or orange.
What is this? [A heater.]
Infrared is another invisible color that our eyes can’t see but we can feel. Infrared feels like heat.
Water is an excellent filter to infrared radiation. Infrared rays that come from space are stopped by water molecules in the air. Infrared observatories must therefore be at high altitudes so they are above most of the moisture in the atmosphere.
VISUAL 14 (still): WISE
Show an artist rendition of the Wide-Field Infrared Survey Explorer (WISE) satellite.
You probably suspected this, too: infrared observatories in space. How much higher can you get? Well, we probably could get higher but it wouldn’t make much difference since this telescope, the Wide-Field Infrared Survey Explorer (WISE), is above all of the water vapor in the atmosphere.
VISUAL 15 (still): IR Scan of Milky Way
Show a WISE all-sky image of the Milky Way galaxy in infrared.
Fade off all infrared images.
DIGITAL EFFECT (optional): IR Sky
If viable on your system, show the infrared sky. This can be used to illustrate what the whole sky would look like if humans had infrared-sensitive eyes.
Here’s a picture of the infrared radiation (heat) that comes from our galaxy, the Milky Way.
VISUAL 16 (still): Microwave Oven
Show an image of a microwave oven, as an example of Microwaves (which are next to Radio Waves in the electromagnetic spectrum).
Alright! Another household item!
What is this? [Microwave oven.]
Microwaves are another invisible color! Did you know that you can cook your food by shining some colored light on it?
Microwaves are really a special form of radio waves which we can use for communications. These radio towers can have rock music blasting all around by sending it in the form of radio waves.
A radio dish antenna can be used to receive radio waves from space. Is rock music what we’ll hear when we point our radio telescopes at space?
Nope! No alien rock stars yet. This is a picture of another supernova remnant, known as the Crab Nebula, in the constellation of Taurus. The supernova occurred in 1054 AD, and was observed by ancient Chinese astronomers and Native American sky watchers. The nebula is roughly 10 light-years across, and it is about 6,000 light-years from Earth. The supernova explosion left behind a rapidly spinning core, known as a pulsar. The pulsar generates a highly energetic "wind," which energizes the material originally thrown off by the star in the supernova explosion. This, in turn, causes the nebula to emit the radio waves seen in this image.
Fade off all Radio Wave images.
DIGITAL EFFECT (optional): Microwave Sky
If available on your system, show the microwave sky. This can be used to illustrate what the whole sky would look like if we had microwave-sensitive eyes.
DIGITAL EFFECT (optional): Gamma Ray
If available on your system, show the gamma ray sky, as another example of an invisible color wavelength astronomers study. This can be used to illustrate what the whole sky would look like if we had gamma ray-sensitive eyes.
So astronomers make use of the entire electromagnetic spectrum to study the Universe. If we only looked in the visible part of the spectrum—the tiny fraction that human eyes can perceive—we'd be missing a lot!
VISUAL 20 (movie): Solar Event in Multiple Wavelengths
Show a video clip of a solar flare event as seen by multiple spacecraft in multiple wavelengths.
In this case, we are looking at a solar flare event that was observed by three different spacecraft. Each spacecraft had its own suite of instruments tuned to observe the Sun through multiple filters. It starts out with a wide-angle view of the Sun, and then zooms into the flare event, and then back out the to see the expanding bubble of energy that results from the flare. The different colors we see correspond to different filters being applied to the view. We see the event in visible light, X-rays, ultraviolet, and more. It is only by putting together all the filtered imagery that we are able to build a complete picture.
Have a bottle with tonic water ready.
In a moment, I am going to turn on some special lights that contain blue, violet and ultraviolet light. We will see the blue-violet but we cannot see ultraviolet; we may detect the ultraviolet by looking at certain objects in this room. Besides hydrogen, there are many other natural detectors of ultraviolet light. Here I have a bottle with "tonic" water, the kind that you buy in a store to drink.
Display the bottle.
When I turn on the ultraviolet light, the chemicals in water will glow in a special way. This phenomenon is called "fluorescence." Certain chemicals in the water absorb the ultraviolet and reradiate it as visible light, just like the nebulae in the pictures we just saw.
Turn on the UV lights. Some audience member’s clothing will fluoresce because of dyes or chemicals used in laundry detergents to "brighten" the clothes. The Sun’s ultraviolet rays cause the "brighter-whites-look" outside. Sometimes even teeth will fluoresce if a student gives a nice toothy grin. Have they been using fluoride toothpaste?
When we think of the wide range of colors in the universe, the few visible colors and the very many colors invisible to our eyes, it is apparent that we humans are nearly blind to most of what’s happening around us. Only by developing better instruments and techniques can we overcome our limited sight.
Before we go, are there any more questions about colors, light, space or anything else related to this program?
Wait several seconds looking around the planetarium for any raised hands. Answer questions in familiar "Colors from Space" terms.
Thank you all for visiting with us today. On your way out, please deposit your color analyzers in this box.
Show box, then place it near the exit.
I hope all of your colors may be happy.
DIGITAL EFFECT: Back to Daylight
Slowly advance time to approximately one hour after sunrise. By going to morning, the daylight can be used for extra illumination as visitors exit the theater.
Apfel, Necia H., Astronomy Projects for Young Scientists, New York: Prentice-Hall Press, 1984. 120 pp. Grade level: 7 and up. A collection of astronomy projects: building a theodolisk; sundials; telescope making; spectroscopes; planetariums; models; observing the Sun, Moon and planets; and variable stars. Includes an appendix of resources, contests and competitions.
Asimov, Isaac, Astronomy Today, Milwaukee, WI: Gareth Stevens Publishing, Isaac Asimov’s Library of the Universe, 1990. 32 pp., hardbound or paperback. Grade level: 3–6. Discusses telescopes of modern astronomy, the space telescope, radio astronomy, the electromagnetic spectrum as a tool of modern astronomy, and backyard astronomers. Includes a "Fact File" reference section, a bibliography, a glossary, an index, and color photos and artwork.
Darling, David J., The New Astronomy: An Ever-Changing Universe, illus. Jeanette Swofford, Minneapolis: Dillon Press, Inc., Discovering Our Universe Series, 1985. 55 pp. Grade Level: 3–6. It starts with a question and answer fact section about modern astronomy, and goes on to explain signals from space, the radio telescope revolution, the use of the electromagnetic spectrum in modern astronomy, x-ray astronomy, spectroscopy, gamma ray astronomy, ultraviolet astronomy, infrared astronomy, the big bang, and the space telescope. It includes a glossary, a bibliography, and an index.
Darling, David J., The Stars: From Birth to Black Hole, illus. Jeanette Swofford, Minneapolis: Dillon Press, Inc., Discovering Our Universe Series, 1985. 55 pp. Grade Level: 3–6. It starts with a question and answer fact section about the stars, and goes on to explain the life and death of a star, twin stars, giants and dwarfs, constellations, clusters, galaxies, and facts about well-known stars. It includes a glossary, a bibliography, and an index.
Gallant, Roy, Fire in the Sky: The Birth and Death of Stars, illus., New York: Macmillan, Four Winds Press, 1978. 130 pp. Grade Level: 7 and up. It discusses the characteristics of star using the Sun as an example, covering the composition of the Sun, various theories about its energy production, differences among the stars, the birth and death of stars. It includes a glossary and an index.
Gianopoulos, Andrea. "Enlightenment" in Astronomy. June 1999, p. 50.
O’Mara, Stephen James. "The Colors of Mars: Reality and Illusion" Sky & Telescope. April 1999, p. 86.
Young, A. "What Color is the Solar System?" Sky & Telescope, May 1985, p. 399.