Planetarium Activities For Successful Shows™
by Cary I. Sneider and Alan D. Gould
revised by Toshi Komatsu
Moons of the Solar System was designed for public audiences and for school children in grades four and above. Presentations for younger age children (grades 1-3) require simplification as noted in the script.
The program begins with students observing how the Moon changes position and apparent shape during a two week time period. To better understand their observations, each student models the Earth-Moon-Sun system with a light in the center of the planetarium representing the Sun, a hand held ball as the Moon, and the student’s own head as the Earth. This is the best way we have found for anyone (including adults) to understand why the Moon goes through phases. The model is also used to explain lunar and solar eclipses.
In the next activity, students observe the moons of Jupiter. Classes of children in grades 4 and up will be able to plot the Galilean moons’ positions on a data chart. Younger groups will watch the moons’ positions change from night to night and draw conclusions from those observations without attempting to record them.
The last part of the program is a tour of the Solar System to see the moons of each planet through the eyes of spacecraft that have visited those planets. Viking, Voyager, Galileo, and Cassini images are featured.
We would be very grateful to hear from you about how you used this program, what modifications you made, what worked well, and what didn’t work well.
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 planetarium controls, the demonstrations, and the 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
Set up the sky for the beginning of the program. Use January 11, 2008 as the start date, since the program calls to start with a waxing crescent moon before sunset. The presenter may use a series of stops for the “Observing Phases of the Moon” activity.
Note: It is useful to modularize portions of the setup. This allows, for example, for random access of phases. Note on Images: For any images in this show, the user may want to adjust the locations of individual images for better positioning in their own dome.
If needed, there are some optional effects that may be used during the “Observing Moon Phases” activity:
Good afternoon! It is getting close to sunset in our planetarium, but before it gets dark, let’s find both the Sun and Moon in the sky right now. It is a common misconception that the Sun and Moon are never up at the same time, but in fact, they often are.
Can you see the Sun and Moon?
Let students use the light pointer to point them out.
Please take careful note of where the Moon and Sun are located while I switch on our planetarium “time machine” to accelerate the sunset.
Turn on music. Slowly turn down cove lights.
DIGITAL EFFECT: Go to Night
Start diurnal motion on slow for a leisurely sunset. Go to approximately 90 minutes past sunset. This parameter may need to be adjusted for your particular theater’s location.
Even though the Sun is now below the horizon, we know about where it is because we saw where it just set.
Point out place on horizon where the Sun set.
We can still see the Moon.
How would you describe the shape of the Moon right now? [Crescent, banana, finger nail clipping.] If we were to watch the sunset from this same spot three or four days from now, do you think the Moon would look the same? [No.] How might it be different? [Different shape; different location.]
The Moon could change its shape in one of two ways, getting fatter or getting thinner. If you think that in three days the Moon will appear narrower, please indicate so by raising your hand. Raise your hand if you think the Moon will appear fuller three or four days from now. Let’s see if our predictions are correct by moving ahead in time using our time machine.
For young audiences, have them count the days going by with you.
DIGITAL EFFECT: 4 Days to Quarter
Run diurnal forward 4 days in 4 seconds to get to a quarter moon phase. During this time, the Moon and stars are off, and the atmosphere and Sun are on. This gives the effect of seeing the Sun race across the sky and making the daylight flash to give the illusion of time passing by quickly. Then, turn on the Moon and turn off the atmosphere and Sun.
Those who thought the Moon would grow fatter are indeed correct.
What shape would you say this Moon is now? [Half Moon.]
Oddly enough, and for reasons that you will learn in a few minutes, astronomers refer to this shape of Moon as a “quarter Moon.”
Is the Moon in the same place as it was when it was crescent, three days ago? [No.] Does it seem closer to or farther from the Sun? [Farther.]
Guess where you think the Moon will be and what shape it will be three days from now.
DIGITAL EFFECT: 3 Days to Gibbous
Run diurnal forward 3 days in 3 seconds to get to a gibbous moon phase. As with the jump before, the Sun races across the sky and the daylight flashes during the time travel. Advance daily motion forward such that the Sun is guaranteed to be below the horizon.
Was your guess correct?
When the Moon is this shape, bigger than quarter but not yet full, it is called a “gibbous Moon.” It seems even farther from the Sun than when it was quarter. Let’s step just three or four more days into the future. Again, try guessing where the Moon will be.
DIGITAL EFFECT: 4 Days to Full Moon
Run diurnal forward 4 days in 4 seconds to get to a full moon phase. As with the jump before, the Sun races across the sky and the daylight flashes during the time travel.
The presenter may continue to view the waning phases. Run diurnal motion until just before sunrise. Then the presenter may view the Moon at its respective phases: "4 days to gibbous", "3 days to quarter", "4 days to crescent", and "4 days to new moon". Do this without seeing the Sun and daylight flash by. Instead, leave the Moon on so the audience can observe the Moon shrinking and moving in the sky (during the waxing phases, the point was for the audience to make predictions). However, the standard delivery of this show would skip the viewing of the waning phases.
The Moon is very nearly full. Remember where the sunset occurred. Note that the Moon is all the way on the other side of the sky from where the Sun is setting. Whenever a full Moon occurs, you can expect it to rise in the eastern part of the sky right around the time of sunset. The different shapes of the Moon that we observe are known as phases of the Moon.
Why does the Moon seem to change shape as we have just observed? [Accept any answers.]
VISUAL 1 (still): Full Moon
Put up a large still image graphic of the Full Moon, for use with a moon phase story.
Practically every culture throughout human history has come up with a different explanation in answer to that question. One rather interesting theory was invented by the Egyptians who believed that a new Moon was born each month (literally) and it grew and grew until it was full. At the moment the Moon reached the fullness of maturity, a giant pig attacked it and kept feasting on it for the rest of the month until there was no Moon left, at which time a new Moon was born.
Do you think that’s really how the Moon changes its shape?
Even though we don’t believe this explanation now, in its time this was a perfectly good explanation and accounted for the phases of the Moon quite well.
The theory most accepted in modern times has to do with relationships between the Earth, Sun, and Moon. To see how this works, let’s make a working model.
Will everyone please stand up?
VISUALS (alternative movies): Moon Phases
If you do not have the ability to do the live demonstration, you may alternatively use the Moon Phase Activity movies provided in the AlternativeMedia folder. Continuous movies go through all of the moon phases, whereas other movies are split into segments to show parts of the Moon cycle separately. Split views contain two views of the Moon modelling experience, one from Earth and one from Space. Separate videos for Earth and Space views are also provided for you to place anywhere you like on the dome.
Turn on the white light (tubular bulb) to about 1/2 brightness.
Let’s pretend that this light is the Sun. Pretend that your head is the Earth. All you need to complete the model is the Moon.
Give each student a ball on a stick.
Hold your Moon so that it is directly in front of the Sun.
Does your Moon look dark? [Yes.]
At this time of month, in reality, the Moon is so dark you could not see it at all. The Moon doesn’t stay in one place; it orbits (goes around) the Earth. Slowly move your Moon to your left, just beginning the orbit of the Moon around the Earth (your head). Move the Moon until you see a small part of it lit by the sunlight.
Go around and check to see each student understands and is observing the crescent Moon.
What shape would you call that lit part of the Moon? [Crescent.] Does it look like the shape of the Moon when we first saw it in the planetarium sky today? [Yes.]
Now continue the Moon in its orbit, moving it slowly to the left, until you see a half disc lit up, which you may recall is the quarter Moon. Notice that when the Sun is setting, from your viewpoint, the first quarter Moon is directly overhead.
Continue moving your Moon in its orbit until you see the gibbous Moon (nearly full). Now try to hold your Moon in a place where it is fully lit and could be called a full Moon.
Let the students discover the shadows of their heads. If necessary, hint that they hold their Moons above those shadows.
We have now modeled the Sun-Moon-Earth system so that we have seen everything that we observed in the planetarium sky. The lit part of the Moon grew from nothing to full and in reality it takes about two weeks for it to do that. However, the Moon does not stop there in its orbit.
What do you think happens as the Moon continues in its orbit? [It appears to get smaller.]
Try slowly moving your Moon the rest of the way in its orbit around its Earth. Try going slowly through a couple more orbits so you can observe the complete cycle of the phases of the Moon. In reality, it takes about one month for the Moon to complete such a cycle (29.5 days, to be exact; for young students it is fun to refer to this as a “Moonth.”)
While we have this model working, let’s see if we can explain a couple of other kinds of events that have startled and terrified people through the ages. Hold your Moon right in front of the Sun so that it blocks the Sun.
What is the name for the event in which the Moon blocks the Sun? [Solar eclipse.]
While you hold your Moon so that it blocks the Sun, look around the room at the other “Earths” which are other peoples’ heads.
Do you see the shadows of their Moons on them? What phase must the Moon be in for there to be a solar eclipse? [New.]
In the real Sun-Earth-Moon system, that shadow of the Moon on the Earth during a solar eclipse is only about 80 km (50 mi) wide. In comparison, the whole Earth is about 13,000 km (8000 mi) wide. During a total eclipse of the Sun, only people located in that narrow shadow region can see the eclipse.
Now move your Moon around until it moves into the shadow of the Earth (your head).
What is this type of eclipse called? [Lunar eclipse.] What phase must the Moon be in for there to be a lunar eclipse? [Full.]
People on the whole night time half of the Earth, the half that points away from the Sun, can observe a total lunar eclipse.
Could people who live on the back of your head see the Moon move into the Earth’s shadow? [No, it’s daytime for them.]
Many more people have seen lunar eclipses than have seen solar eclipses. This is because whenever a lunar eclipse occurs, people on half of the Earth have the opportunity to see it, but to see a solar eclipse, you must be where the comparatively tiny shadow of the Moon sweeps across the Earth.
Collect Moon balls.
So far, we have observed the moon just as our ancestors did, thousands of years ago. About 400 years ago, telescopes were invented and exciting new views of the moon were possible. Let’s see how our moon looks through a telescope.
DIGITAL EFFECT: Telescopic Moon
Run through the images for the “The Moon Through a Telescope” and “The Galilean Moons of Jupiter” sections. First scale up a modest telescopic view of the Moon.
You may want to allow for random access of the images, especially in case someone in the audience needs to see a previous night (e.g., going back to see Night 5 when viewing Night 7). In normal operation, however, the non-modularized portions should be all you need for the tracking activity.
VISUAL 4 (still): Moon Through a Telescope
Pretend we are looking through the eyepiece of a telescope. Let’s aim it at the moon.
What features can you see? [Dark areas, light areas, little circle.]
The light areas are mountainous regions.
What type of terrain do you think we would find in the darker areas? [Flat.]
The first person to carefully examine objects in the sky through a telescope was a man named Galileo Galilei, an Italian scientist who lived about 400 years ago. He also thought those dark areas were flat, but he called them “maria,” the Italian word for ocean.
Do you think they are really oceans? [There really is very little water on the moon, and certainly no oceans.]
Galileo also looked at the planet Mars and saw how it looked different from stars. Stars are much farther away and look like pinpoints of light, while nearby planets such as Mars can be seen as balls through a telescope.
DIGITAL EFFECT: Telescopic Mars
Scale the Moon image down, and scale up a modest telescopic image of Mars.
Galileo also looked at Jupiter.
DIGITAL EFFECT: Telescopic Jupiter
Scale the Mars image down, and scale up a modest telescopic view of Jupiter with the four Galilean moons visible.
VISUAL 6 (still): Jupiter and 4 Moons
He saw the planet Jupiter with four small objects in a line near it. Galileo thought the objects were stars, but when he observed Jupiter on subsequent nights, those “stars” appeared in different places. This was quite upsetting (and intriguing), since patterns of other stars never change relative to one another from night to night. Galileo kept careful records of the positions of Jupiter’s companion “stars.”
VISUAL 7 (still): Galileo’s Notes
Fade on a copy of Galileo’s notes, from his observations of Jupiter’s moons in 1610.
Don’t worry if you can’t read the words. It’s written in Italian. Each night Galileo recorded the positions of Jupiter (use arrow to indicate), and its 4 companion “stars.”
Do you think they are really stars? [No.] What else could they be? [Moons!]
Galileo determined that they were moons. Let’s see why. Let’s watch Jupiter and its moons for a few nights just as Galileo did. Here is some astronomical note paper for you to note the changing positions.
Hand out a “Tracking Jupiter’s Moons” sheet to each person.
One sticky problem Galileo had was trying to tell which “star” was which. Let’s make our job easier by doing something Galileo could not: color each moon a different color.
VISUAL 8 (still): Jupiter and Moons Color Coded
Fade up a similar image to the telescopic view of Jupiter above, but with the moons individually color-coded, labeled, and with distance markers on the image.
Let’s further simplify our task by specializing: look at only one moon at a time.
Divide the class into four groups and assign each group one “star” to keep track of. Point out the color and name of each moon. Also point out the numbers that indicate distance from Jupiter in millions of miles. For younger classes (grades 1-2), do not hand out paper. Do not divide the class into groups. Have the entire class observe one moon at a time.
VISUAL 9 (still): Full Moon
Bring up the view of the moons on “Night 1” of the “Galilean Moons of Jupiter” tracking activity. This is the same image as in "Moon Labels", but with the labels removed for easier reading.
Here is our view for our first night’s observation. Please put a mark on your “Night 1” line indicating the position of your moon as you see it in relation to Jupiter.
Go around and check to see that each student understands. Help as needed.
Now we will let one day go by to arrive at “Night 2.” Then we will let a second day go by to arrive at “Night 3.” After eight days have gone by, we will have arrived at “Night 9.” Each night, mark where your moon is with respect to Jupiter on the appropriate line.
VISUALS 10–17 (still): Tracking Nights 2–9
Cross-fade through the images for Nights 2 though 9. If an audience member needs to view a night already seen, fade off the current night, and then use a modular sequence to show the desired night again.
By now, you can see why Galileo concluded that his odd “stars” must really be moons.
How can you tell they are moons, not stars? [They move back and forth, “around” Jupiter.]
A moon orbits a planet. These moons seem to move back and forth in a straight line because we see their orbits from the side. If we could see Jupiter from above its North Pole, we would see these moons go around Jupiter.
How could you tell how many days it takes for your moon to orbit Jupiter? [Count how many days it takes to return to its starting position. Be sure to count just the spaces in between the nights to get a correct answer for the number of days gone by.]
Ask a member of each group to report the orbital period of the moon that s/he tracked.
Can you see any relationship between the farthest distance each moon gets from Jupiter and the time it takes to orbit Jupiter? [The more distant moons go around more slowly.]
Not all four moons are visible all the time. Sometimes one or more moons are in front of or behind Jupiter and cannot be seen.
We are not completely satisfied to look at moons in our Solar System through telescopes. Let’s take a spaceship ride to some of the planets in our Solar System to get close-up views of their moons. While this is an imaginary spaceship ride, we will view real images transmitted to Earth by Viking and Voyager spacecraft. Please fasten your (imaginary) seatbelts while we prepare to lift-off.
In many cases, the moon images that follow do not need to be shown, as 3D models can be used. Images of surface closeups can be included within the programmed effects.
If certain native model imagery is already available in the fulldome digital system, the presenter should use the software platform's native models wherever possible. Stills in the script then provide examples of the type of view desired to show audiences.
If no model is available in the fulldome digital system, then the images provided should be used.
Start rocket launch sound effect at countdown.
DIGITAL EFFECT: Begin TourTurn covelights off.
At ignition, start blue daylight and orange covelights alternating in intensity. Turn on stars. Start diurnal motion and gradually accelerate while rocket noise gets louder. As rocket noise subsides, gradually bring diurnal motion to zero and dim daylight.
DIGITAL EFFECT: Begin Tour
Start the solar system tour. Lift off Earth and view it from space. Do a slow orbit around Earth
Before we leave the neighborhood of Earth, let’s get a super view of our own Moon.
DIGITAL EFFECT: Orbit On
Show the orbit line of the Moon.
DIGITAL EFFECT: Polar View
Move Earth to the zenith and put the Moon’s orbit line roughly parallel to the dome horizon.
DIGITAL EFFECT: Luna
Scale up the size of the Moon to make it more visible.
VISUAL 19 (still): Crater (Clementine image of Tycho)
An associated image with the Moon—a Clementine image of Tycho crater. Remove image when finished.
DIGITAL EFFECT: Full Moon
Turn off the Tycho image and scale the Moon back down to default size.
Discuss what craters are and how they are formed. See references for latest info on Clementine, Lunar Prospector, and later missions. There is evidence of water ice in polar regions of the Moon!
If it’s moons we want to see, there is no point in traveling to the two planets Mercury and Venus that are closer to the Sun than Earth. They have no moons at all. Let’s journey outward in the Solar System towards Mars.
Play music for journey to Mars.
DIGITAL EFFECT: Teleport Mars
Turn diurnal motion on. Prepare us for “teleporting” to Mars by turning the sky so that Mars is positioned at the sweetspot, and highlighted with a colored arrow.
DIGITAL EFFECT: Teleport!
Teleport to Mars through a fade out/in. Upon arrival, stop diurnal and begin a slow orbital motion.
Note the shapes of the illuminated parts of Mars and its moon Phobos.
Can you explain those shapes? [Quarter phase.] From which direction is the sun shining?
Have an audience member indicate with battery light pointer.
DIGITAL EFFECT: Orbit On
Turn on the moon orbits for Mars.
DIGITAL EFFECT: Polar View
Move Mars to the zenith, such that the moon orbits are roughly parallel to the dome horizon.
All the digital effects in this section should be programmed in a similar manner—1) move the planet to the sweetspot, 2) “teleport,” 3) show moon orbits, and 4) move the planet to polar view. Some or all of these planets and moons can be shown, as time allows. For the remainder of the tour, the presenter may choose to visit planets and their moons in any order they wish.
Phobos is only about 15 miles (10 km) long. It is very small compared to earth’s moon which is 2000 miles (3200 km) across. If you want to play baseball, but can’t find anyone to play, you could still have a good game on Phobos. The gravity on Phobos is so weak that if you stood on its surface, you could throw a baseball into orbit or beyond (just like Superman on Earth). So, you could pitch the ball in one direction, then pick up your bat and wait for the ball to come at you from the other direction.
DIGITAL EFFECT: Phobos
Zoom in on Phobos for better viewing.
Zooming effects are to make a given moon more visible. Some moons have an associated still image or two, so show that image (if available), and then turn the image off and zoom out from the moon.
Mars may have a small moon compared to earth’s moon, but it has an extra moon just for good measure. This moon Deimos is only a bit smaller than Phobos.
DIGITAL EFFECT: Deimos
Zoom in on Deimos for better viewing.
Let’s head on to the next planet out in the Solar System.
Anyone know which planet that is? [Jupiter.]
Music up for cruise to Jupiter.
Let’s see those four moons we tracked before. They each have unique markings and geology.
DIGITAL EFFECT: Teleport Jupiter
Run through the “teleport” sequence—preparation, teleport, orbit lines, polar view (with stops)—for Jupiter, as we did with Mars (above).
VISUAL 23 (still): Jupiter and Moons
The Galileo spacecraft arrived at Jupiter on December 7, 1995. Galileo’s atmospheric probe plunged into Jupiter’s atmosphere and relayed information on the structure and composition of the Solar System’s largest planet, while the Galileo orbiter studied Jupiter and its moons, encountering one moon during each orbit.
DIGITAL EFFECT: Callisto
Zoom in on Callisto for better viewing.
VISUAL 25 (still): Global Callisto in Color (NASA Galileo mission)
Callisto (the “white moon” we tracked) is pockmarked with ancient craters, easily visible as bright scars on the darker surfaces. In fact, Callisto is the most heavily cratered object in the Solar System. The crust of this moon shows remnant rings of enormous impact craters. The largest craters have apparently been erased by the flow of the icy crust over geologic time. The brighter craters seen here are thought to be mainly ice.
VISUAL 26: Callisto Scarp Mosaic (NASA Galileo mission)
Show a still image of a Callisto surface closeup.
In this close-up, we can see lots of craters, and a very steep slope—or scarp—crossing the image. This scarp is just a small part of a much larger multi-ringed crater structure 4,000 kilometers (2,485 miles) in diameter.
DIGITAL EFFECT: Ganymede
Zoom in on Ganymede for better viewing.
VISUAL 27 (still) : Global Ganymede in Color (NASA Galileo mission)
Ganymede (the “blue moon” we tracked) has frosty polar caps as well as two other types of terrains: bright, grooved terrain and older, dark furrowed areas. The two types of terrain suggest to us that Ganymede’s entire icy crust has been under tension from global tectonic processes. Ganymede is the largest moon in the Solar System—5,276 kilometers (3,280 miles) in diameter.
VISUAL 28 (still): Ganymede—Mixture of Terrains (NASA Galileo mission)
Show still image of a Ganymede surface closeup.
The image shows fine details of one of the brighter areas of Ganymede, and reveals a mixture of terrain. One part is older and heavily cratered; one part is younger with line-like structures and an impact crater. Seeing terrain like this side-by-side allow scientists to work out the complex geology of Ganymede.
DIGITAL EFFECT: Europa
Zoom in on Europa for better viewing.
Europa (the “yellow moon” we tracked) is one of the smoothest moons in the Solar System, and only slightly smaller than Earth’s Moon. With Europa’s surface temperature of -260° F, it is completely covered in ice. The lines we see here are cracks in that ice. We expected to find quartz-hard ice like on Ganymede, but we find evidence that slush or even liquid water is beneath the moon’s surface. The warmth from a tidal tug of war with Jupiter and neighboring moons could be keeping large parts of Europa a liquid ocean.
VISUAL 31 (still): Europa—Ice Rafting View (NASA Galileo mission)
Show still image of a Europa surface closeup.
Large plates of ice seem to be sliding over a warm interior on Europa, much like Earth’s continental plates move around on our planet’s partly molten interior. Some recent images show features that have many similarities to new crust formed at mid-ocean ridges on the Earth’s sea floor.
Europa may be slushy just beneath the icy crust. There are chunky textured surfaces like icebergs, an area littered with fractured and rotated blocks of crust, and gaps where new icy crust seems to have formed between continent-sized plates of ice. Rough and swirly material between the fractured chunks may have been suspended in slush that froze at the very low surface temperatures. Studies of craters on Europa show that they are relatively young and that subsurface ice is warm enough to collapse and fill them in time periods that are short, geologically speaking.
The combination of interior heat, liquid water, and organic material falling onto Europa from comets and meteorites means that Europa has the key ingredients for life, making this moon a laboratory for the study of conditions that might have led to the formation of life in the Solar System.
DIGITAL EFFECT: Io
Zoom in on Io for better viewing.
VISUAL 32 (still): Global Io in Color (NASA Galileo mission)
Io (the “red moon” that we tracked) is the closest Galilean moon to Jupiter and is slightly larger than Earth’s Moon. It is quite a startling contrast to other moons we have seen. Most of the craters seen here were not created by impacts, but by volcanoes!
VISUAL 33 (still) : Active Volcanic Plumes on Io (NASA Galileo mission)
Show still image of a volcano erupting on Io.
It is the most volcanically active body in the Solar System, sizzling with dozens of molten sulfur and silicate volcanoes. Most bodies in the Solar System do not have radical surface changes that are noticeable over short periods of time. But several such changes have been observed on Io between the times of the Voyager spacecraft visits to Jupiter in 1979, when no fewer than nine simultaneously erupting volcanoes were seen, and the Galileo mission of 1989-2003. The extreme volcanic activity is caused by Jupiter’s gravity generating 100 meter (330 ft) high tides in its otherwise solid surface. In this color enhanced image, deposits of sulfur dioxide frost appear in white and grey hues, while yellowish and brownish hues are probably due to other sulfurous materials.
VISUAL 34 (still): Arizona-sized Io Eruption (NASA Galileo mission)
Show side-by-side comparison of before and after a volcanic eruption on Io.
The image on the left shows a before picture of a region of Io. The image on the right was taken when the Galileo probe returned some time later, and a new dark spot is visible. This appears to be from a plume that rose 120 kilometers (75 miles) high and then deposited the material in an area about 400 kilometers (250 miles) in diameter—roughly the size of Arizona!
Bright red materials, such as the prominent ring surrounding the volcano named Pele, and black or dark gray spots with low brightness mark areas of recent volcanic activity and are associated with high temperatures and surface changes.
Io acts as an electrical generator as it moves through Jupiter’s magnetic field, developing 400,000 volts across its diameter and generating an electric current of 3 million amperes that flows along the magnetic field to the planet’s ionosphere.
The Galileo mission was supposed to end December 1997, but the spacecraft was in excellent shape so its duties were extended to include eight more encounters with Europa (Dec. 1997–Feb. 1999) and two more encounters with Io on Oct. 11, 1999, and Nov. 26, 1999. The extra Europa encounters were aimed at possibly confirming that an ocean presently exists on Europa, and locating some areas where the ice is thinnest. This would lead the way to possible future Europa orbiting or ice drilling missions looking into a key question for the 21st Century—is there life on Europa?
Let’s move on to the next planet out in the Solar System, the most beautiful one for many people: Saturn.
DIGITAL EFFECT: Teleport Saturn
Run through the “teleport” sequence—preparation, teleport, orbit lines, polar view (with stops)—for Saturn, as we did with Mars (above).
Saturn has at least 60 known moons orbiting at distances ranging from 134,000 kilometers to 13 million kilometers (84,000 miles to 8 million miles) from Saturn. The planet itself is not as colorful as Jupiter. It does have a similar banded appearance, but the zones are not as obvious, perhaps because they are partly obscured by higher layers of atmosphere.
Here we see the delicate rings casting shadows on the gas giant. Saturn’s colors gradually change from gold to bluish as you move towards its north pole, but scientists don’t fully understand why. It may be a seasonal effect, resulting from the cold winter temperatures.
DIGITAL EFFECT: Mimas
Zoom in on Mimas for better viewing.
VISUAL 39 (still): Mimas (NASA Cassini mission)
Show still image of Herschel crater.
This little moon of Saturn is about 400 km (250 mi) across and is made of almost solid ice at -180°C (-300°F). A prominent impact crater can be seen here, almost 1/3 the diameter of Mimas. Images of the other side of Mimas show a large rift which could imply that the impact that caused this crater nearly cracked Mimas into two (or more) pieces.
DIGITAL EFFECT: Iapetus
Zoom in on Iapetus for better viewing.
VISUAL 40 (still): Iapetus (NASA Cassini mission)
This is Iapetus, one of the outermost moons of Saturn. From your knowledge of phases, which direction is the sunlight coming from in this image?
Use pointer to indicate various directions as you poll the audience.
This is actually a trick question because the position of the Sun when this image was made would have been behind us. We would thus expect to see Iapetus in a full phase. This and other images made of Iapetus indicate that one side of it has really dark material on it. The dark side happens to be the leading side of Iapetus with respect to its orbital motion. That’s another puzzle for the planetary geologists, as yet unexplained.
VISUAL 41 (still): Ridge on Iapetus (NASA Cassini mission)
Show still image of Iapetus, with a close up of the equatorial ridge.
Iapetus also has a remarkable ridge that runs around almost the entire moon, closely following its equator. The peak of the ridge reaches over 10 kilometers (6 miles) in height. Where the ridge came from is still unknown. It could have formed from internal material oozing thorough a crack on the surface, or perhaps an ancient ring that once encircled Iapetus crashed onto its surface.
DIGITAL EFFECT: Titan
Zoom in on Titan for better viewing.
VISUAL 42 (still): Titan Atmosphere (NASA Cassini mission)
Show still image of Titan with atmospheric haze.
Titan is almost as large as Jupiter’s moons Ganymede and Callisto. But unlike those moons, Titan is able to retain an atmosphere. It can hold an atmosphere because it is in a colder part of the Solar System. Any gases near Ganymede or Callisto would be warm enough and energetic enough to escape the gravity of those moons. Titan’s cold atmosphere is mostly nitrogen, but is thickly laden with various hydrocarbons that some of the Voyager scientists have jokingly compared with Los Angeles smog. The atmosphere is so thick and opaque that until recently we were denied images of the surface of Titan. Measured temperatures are just about cold enough that pools of liquid ammonia, liquid methane, or liquid nitrogen could exist on the surface.
VISUAL 43 (still): Lakes on Titan (NASA Cassini mission)
Still image of Cassini radar data, showing lakes on Titan.
The Cassini spacecraft arrived at Saturn in June 2004 and still is operating (as of March 2011).
As part of the Cassini mission, we got our first detailed data from Titan and its surface. In January 2005, the European Space Agency’s Huygens probe drifted through the atmosphere for three hours before touching down on the surface. However, Cassini visited Titan multiple times, taking radar images of the surface. The north pole of Titan has been confirmed to have giant lakes and seas, with at least one larger than Lake Superior. These lakes seem to form from liquid methane and ethane that rains down on this extraordinary moon where the temperature is -179°C (-290°F). Images also showed rocks or ice blocks and possible methane or ethane ground fog on surface, clouds, and drainage channels.
There are still many mysteries about Saturn—how did the system of Saturn’s satellites form? How are they continuing to evolve? What is the relationship between the icy satellites and the rings of Saturn?
VISUAL 44 (still): Saturn’s Rings (NASA Cassini mission) Bring up a still image of Saturn’s rings, as viewed from the Cassini probe.
Through the best Earth telescopes, Saturn appears to have only four rings. But as our spacecraft approaches, we see they are made of dozens, indeed hundreds of narrow “ringlets.” The rings of Saturn are made of particles of ice, dust and rock. The particles range in size from a grain of sand to something larger than this planetarium. They are all orbiting Saturn as if they were each a tiny “moonlet.”
DIGITAL EFFECT (optional): Enceladus
Zoom in on Enceladus for better viewing.
Note: This moon is optional to show. However, the user may wish to add their own images of the recently discovered ice geysers on Enceladus.
Now it is time to move on to Uranus. Voyager encountered Uranus on January 26, 1986. Here is an accelerated version of what you might have seen if you had been on board. This is a computer generated simulation of the encounter.
DIGITAL EFFECT: Teleport Uranus
Run through the “teleport” sequence—preparation, teleport, orbit lines, polar view (with stops)—for Uranus, as we did with Mars (above).
This is a collage of Uranus and its ring system as if you were standing on Uranus’ moon Miranda. Uranus has a paltry ring system compared with that of Saturn; only ten thin rings were seen. Notice the deep canyon and impact craters in the icy surface of Miranda. (Miranda and Uranus in this picture are Voyager 2 images, while the rings are artist’s conception. The apparent blue color of Uranus is its true color and is a result of the absorption of red light by methane in Uranus’ atmosphere, leaving primarily blue light to reflect back.)
Here is a great image of Miranda, which is about 480 km (300 mi) in diameter.
DIGITAL EFFECT: Miranda
Zoom in on Miranda for better viewing.
VISUAL 49 (still): Miranda Surface, Cliffs 10-15 kilometers (6-9 miles) high (NASA Voyager 2 mission)
Show still image of a Miranda surface closeup.
Voyager also detected 10 new moons, bringing the total number of Uranian moons to 15 at that time (as of 2003, we count 27 moons). Remember that these images were transmitted across more than a billion miles of space by a spacecraft that had already endured encounters with Jupiter and Saturn in its 9-year odyssey through the Solar System. (Voyager was launched in 1977.)
DIGITAL EFFECT: Titania
Zoom in on Titania for better viewing.
Five large moons of Uranus were known before the Voyager 2 encounter. In order of increasing size, they are Miranda, Ariel, Umbriel, Titania, and Oberon. Titania is one of the largest, about 1,600 km (1,000 mi) in diameter, roughly half the size of Earth’s Moon. Titania, for example, is marked by huge fault systems and canyons that indicate some degree of geologic activity in its history. These features may be the result of tectonic movement in its crust.
Voyager has survived its Uranus encounter in which it performed beyond our wildest dreams. It went past Neptune in an encounter in August of 1989.
DIGITAL EFFECT: Teleport Neptune
Run through the “teleport” sequence—preparation, teleport, orbit lines, polar view (with stops)—for Neptune, as we did with Mars (above).
Voyager 2, a senior citizen spacecraft having spent 12 years of rigorous journey through space with three spectacularly successful encounters under its belt, performed superbly in its encounter with Neptune. It allowed us to discover 6 new Neptunian moons, bringing the total number for Neptune to 8 at that time. As of 2008, we know of 13 moons.
DIGITAL EFFECT: Triton
Zoom in on Triton for better viewing (manual zoom recommended).
Voyager 2 sent us spectacular images of the huge moon Triton, revealing ice volcanoes. Voyager 2, its primary mission complete, is now on its way to exit the Solar System, never to return.
As exciting as the Voyager images are, we must not forget about important discoveries made by astronomers with Earth-based telescopes.
Observations obtained by NASA’s Hubble Space Telescope and ground-based instruments reveal that Triton seems to have heated up significantly since the Voyager spacecraft visited—it has been undergoing a period of global warming. The warming trend is causing part of Triton’s frozen nitrogen surface to turn into gas, thus making its thin atmosphere denser. Even with the warming, no one is likely to plan a summer vacation on Triton, even though its temperature has risen about three degrees to a whopping -234°C (-389°F). If Earth experienced a similar change in global temperature over a comparable period, it could lead to significant climatic changes.
By studying the changes on Triton, the scientists hope to gain new insight into Earth’s more complicated environment.
VISUAL 54 (still): Pluto
Bring up a still image of Pluto and its three satellites, as imaged by Hubble.
Pluto, dwarf planet beyond Neptune, was found to have a large satellite companion in 1978 with the aid of an Earth-based telescope. This satellite was given the name Charon (pronounced “Shar'-on,” after the wife of the discoverer, Charlene). In Greek & Roman mythology, this is the boatman that carries souls across the river Styx to the underworld, in which the god Pluto reigned. In 2005, astronomers discovered two more companions to Pluto, and named them Nix (goddess of the night and mother of Charon) and Hydra (a nine-headed serpent, who kept its den at the entrance of Hades, where Pluto lived). These tiny companions were discovered with the Hubble Space Telescope.
DIGITAL EFFECT: Return to Earth
End the tour. Fade off the entire sky to “instantly” transport us back to Earth orbit. Orbit Earth slowly before landing.
DIGITAL EFFECT: Land
“Land” on Earth by first approaching it, and then fading the scene off. Land back on Earth at your local latitude and longitude on today’s date at noon, and then fade on the scene.
We land you now back at __________________ Planetarium. [Insert your home planetarium here.]
We hope you enjoyed your tour of the moons of the Solar System. You are invited to come back to our planetarium sometime to see our other planetarium shows.
VISUAL 56 (still): Your Planetarium or School
There are some more optional effects which may also be used during the Tour segment:
Toggle Orbits: In some cases, it may be distracting to have or to leave the moon orbits on. For example, Jupiter’s moon orbits are still visible as a green anomaly in the sky as seen from another planet if left on. Toggle the respective planet’s moon orbits off and on.
Lunar Cycle: Scale up the Moon to size 35 and then run though one complete lunar cycle to show the Moon going though its phases in space. Design it to appear similar to what is seen with the moon ball activity. This effect should only be used after putting Earth in “Polar View”.
Hi-Resolution Phobos: Bring up a high resolution image of Phobos from the HiRISE instrument on the Mars Reconnaissance Orbiter (MRO).
Ida/Dactyl: Show a still image of asteroid Ida, with its satellite Dactyl, as an example of non-planets that also have satellites.
Quick Return: An alternate way to end the show is to fade the entire scene off and then fade the scene back on having already landed back on Earth at noon. Thus, you may bypass seeing Earth from space first. To be used in the case of having to end the tour (and the show) the quickest way possible.