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Seeing Saturn Cart - 1 of 7 Seeing Saturn Cart Brief Summary This cart and its props illustrate three different ways that people have recorded images of Saturn, 1) as a simple drawing, 2) as photographs seen from Earth and 3) from spacecraft that have flown near Saturn. The Seeing Saturn Cart allows visitors to wander around the cart and see these three views of Saturn. Equipment Required Seeing Saturn Cart Fig 1- Seeing Saturn Cart Fig 2 – Front display. Notice the hole that serves as simulated telescope view Fig 3 – Rear Display Fig 4 0 Close up of the wheel that turns Seeing Saturn Cart - 2 of 7 Main Teaching Points The purpose of the Seeing Saturn Cart is: 1) To demonstrate how the view of Saturn and its rings from Earth changes as Saturn orbits the Sun. 2) To talk about the history of the discovery and understanding of Saturn’s rings 3) To allow visitors to explore the variety of 2-dimensional shadows made by a single 3 dimensional object, which is similar to what early observers saw with their basic telescopes. Educational Strategy This model provides the opportunity to discuss the 17th Century “Mystery of Saturn’s Rings.” To early observers, the rings seemed to disappear at regular intervals. Solving mysteries is always a crowd pleaser. In addition, the issue of what you see when you shift perspectives is a crucial one to science. Set Up The Seeing Saturn Cart is located by the Experiment on the lower level of Space Odyssey. It is plugged into a timer that has it automatically come on during regular Museum hours. Suggested ways of presenting demo Try this approach, which treats the demo as a guessing game: Suggest that the visitors look at the painted Saturn ball from different views, noticing the tilt of the rings. Have visitors look at the historical drawings of Saturn drawn by Galileo, Huygens and Cassini, and have them speculate why they would have seen Saturn that way. Show visitors the view of Saturn on the rear display (shadows), which would be similar to what early observers would have viewed through their basic telescopes After visitors have explored on their own, have them look through the simulated telescope hole on the front of the cart. Turn the Saturn wheel so that visitors can see the apparent change in the slant of the rings. Have visitors make suggestions as to the cause. Explain to visitors that SATURN DOES NOT CHANGE ITS RING ORIENTATION AS IT ORBITS THE SUN. The apparent change in the tilt of the rings is due entirely to how our view of it from Earth changes as Saturn orbits the Sun. Thus, over the Saturnian year (30 Earth years), the rings appear to precess. To pass from one extreme where the rings appear Seeing Saturn Cart - 3 of 7 mostly open (such as the view Galileo drew) to the edge-on view (when the rings seem to disappear) takes about one quarter of a Saturn year, or 7.5 years. In one could view Saturn from a point outside of our solar system, , Saturn’s rings would always maintain their same orientation of 25 degrees from the Solar system’s North Pole, which is the same as Saturn’s axial tilt. Other Cool Stuff to Try Take interested visitors to the ORBITS TABLE or to the wall mounted pictures of Saturn near the Planetarium entrance. Using the MGG Portal, show visitors the latest Cassini Mission updates Use Starry Night Pro (SNP) or the Orbits Table to show the 60 plus moon of Saturn we now know of. Use SNP top show how to find Saturn tonight. Operating Tips If you wish to move the cart, unplug the cart from the wall in front of the Mars Diorama. Make sure you have access to an electrical outlet near where you would like to facilitate it so that the cart has power. A Quick History of Understanding Saturn’s Rings 1610 1612 1655 1660 1676 1883 1979 1980 & 1981 2004 Galileo discovers Saturn’s rings Galileo notices that rings have disappeared Huygens conjectures that Saturn is surrounded by a solid ring Chapelain suggest rings made up of many small bodies Cassini discovers a gap in the rings of Saturn First photographs of Saturn’s rings Pioneer 11 Spacecraft flies by Saturn’s and takes first close-up pictures Voyage 1 & 2 Spacecraft flies by Saturn and photographs Saturn & its moons Cassini Spacecraft orbits Saturn and drops Huygens probe onto Titan. Cassini's mission is slated to continue through September 2017 Seeing Saturn Cart - 4 of 7 Saturn Fast Facts SATURN DAY SATURN YEAR SIZE DISTANCE TO SUN ORBITAL ECCENTRICITY DENSITY COMPOSITION ATMOSPHERE REFLECTANCE Saturn rotates on its axis every 10.2 hours. Saturn rotates on its axis every 29.5 yr. It takes Saturn over two years to cross through any constellation of the zodiac. This makes it easy to find at night. 120,660 km = 9.5 times Earth 9.5 AU = 880 million miles from the Sun. This means that the Sun seen from Saturn is only about 1.1% as large in area as the Sun is from Earth. Saturn = 0.056; (Earth = 0.017; Mars = 0.093) The practical effect is that when Saturn is at the elongated part of its orbit (aphelion) is not as bright to viewers on Earth. Saturn is brighter at it is perihelion. 0.69 g/ml. This is below the density of water, so Saturn would float on water! rocky core, a liquid metallic hydrogen layer and a molecular hydrogen layer Mainly hydrogen and helium gas Visual albedo = 0.46 (Earth’s moon = 0.11) Source: The Nine Planets @ http://www.nineplanets.org/saturn.html Cassini-Huygens Probe Launch date Saturn arrival date Launch mass Total flight path Power source Communications: Huygens probe release date Oct 15, 1997 July 1, 2004 5,574 kilograms (6.1 tons) 5 billion kilometers (3 billion, 200 million miles) 700 watts of electrical power comes from three radioisotope thermoelectric generators three antennas, operating at microwave frequency. The large white dish on Cassini is the 2-way high-gain antenna November 6, 2004, landed on Titan January 14, 2005 Seeing Saturn Cart - 5 of 7 The Cassini orbiter has: Examined the gravitational field of Saturn, its rings and moons using radio waves Take photos in visible, near-ultraviolet (UV) and near-infrared (IR) light Mapped the surface of Titan using radar Has studied particles around Saturn and its rings and flown by its moons to learn about their atmospheres and ionospheres Study ice and dust grains in the Saturn system Cassini continues to operate in orbit around Saturn and its moons in 2015 and is likely to continue its mission into 2017 The Huygens probe, contributed by the European Space Agency successfully landed on Titan and: Took pictures of Titan's atmosphere and surface Studied clouds, chemical composition, winds and particles in Titan's atmosphere Explored the surface of Titan immediately adjacent to the landing site Questions and Answers Are the rings solid? Though they look continuous from the Earth, the rings are actually composed of innumerable small particles each in an independent orbit. They range in size from a grain of sugar, to the size of a house and everything in between. How thick are the rings? Saturn's rings are extraordinarily thin: though they're up to 175,000 miles in diameter they are only 30 feet thick. Despite their impressive appearance, there's really very little material in the rings -- if the rings were compressed into a single solid object it would be no more than 62 miles across. What are the rings made of? The ring particles are made of water ice as well as some small rocky particles that are coated in ice. How did the rings form? While the exact origin of the rings of Saturn (and the other Jovian planets) is not known, it is thought that Saturn’s rings were probably formed by comets, asteroids, or moons that were pulled into orbit and broken up by Saturn’s strong gravity. As the pieces of these objects continued to orbit Saturn, they collided; creating even smaller pieces that eventually became more evenly distributed and formed the rings. However, the rings are not stable and must be Seeing Saturn Cart - 6 of 7 regenerated by an ongoing process. Enceladus, a moon of Saturn, has geysers of water that may be part of this regeneration process. All we see of Saturn is clouds. Is there a solid planet under the clouds? Saturn's deep interior is similar to Jupiter's consisting of a rocky core, a liquid metallic hydrogen layer and a molecular hydrogen layer. Traces of various ices (water ice is very familiar on Earth, but, methane, and ammonia can also form solids at extremely low temperatures.) Saturn's interior is hot (12000 K at the core) and Saturn radiates more energy into space than it receives from the Sun. Most of the extra energy is generated by the slow gravitational compression of the planet as in Jupiter. But this may not be sufficient to explain Saturn's luminosity; some additional mechanism may be at work, perhaps the "raining out" of helium deep in Saturn's interior. What are Saturn’s clouds made of? Like Jupiter, Saturn is about 75% hydrogen and 25% helium with traces of water, methane, ammonia and "rock", similar to the composition of the primordial Solar Nebula from which the solar system was formed. Winds in the upper atmosphere of Saturn reach up to 1600 feet per second. These super-fast winds, along with heat rising from the core cause the yellow and gold bands visible in the atmosphere. Where did we get our information about Saturn’s clouds? Details in the cloud tops are invisible from Earth so it was not until the Voyager encounters that any detail of Saturn's atmospheric circulation could be studied. Saturn also exhibits long-lived oval and other features common on Jupiter. In 1990, the Hubble Space Telescope observed an enormous white cloud near Saturn's equator which was not present during the Voyager encounters; in 1994 another, smaller storm was observed. Over the course of its mission, Cassini has observed several storms on Saturn, including one in 2010 that was called a “monster storm” because of its intensity and long-lived turbulence. Findings from the Cassini mission revealed the dynamics of Saturn’s storms. The storms on Saturn are similar to convective storms on earth that send air and water vapor high into the atmosphere, creating tall billowing clouds that can be 10-20 times larger than thunder clouds on Earth. Are the rings connected? Two prominent rings (A and B) and one faint ring (C) can be seen from the Earth. The gap between the A and B rings is known as the Cassini division. The much fainter gap in the outer part of the A ring is known as the Encke Division (but this is somewhat of a misnomer since it was very likely never seen by Encke). Using Voyager and Cassini, scientists have found an additional five rings. Some gaps in the rings have moons inside of them (Encke and Keller gaps). These tiny moons keep the gaps between rings open. Saturn's rings, unlike the rings of the other planets, are very bright (albedo 0.2 - 0.6). (Albedo is the fraction of incident light that is reflected.) Seeing Saturn Cart - 7 of 7 What are some of the unsolved issues about Saturn? How does Saturn generate its internal heat? What is the origin of the rings? What does that tell us about the origin of the solar system as a whole? Why are Saturn's rings so much more dramatic than the other gas giants? Source: The Nine Planets @ http://www.nineplanets.org/saturn.html and The Cassini Mission @ saturn.jpl.nasa.gov Potential Problems If moving the cart to a different location, make sure you have an outlet in that location to plug-in the cart. Background materials collections links) (websites, videos, articles, digital http://www.solarviews.com/eng/saturnbg.htm - Historical Background of Saturn’s rings (with diagrams) http://solarsystem.nasa.gov/planets/profile.cfm?Object=Saturn http://www.nineplanets.org/saturn.html - Great Saturn Factsheet http://www.solarviews.com/eng/saturn.htm - Another good Saturn Factsheet http://saturn.jpl.nasa.gov/index.cfm - Cassini-Huygens home page http://saturn.jpl.nasa.gov/kids/index.cfm - Cassini Mission Kid’s Page http://sci.esa.int/cassini-huygens/ -- ESA Cassini-Huygens home page