Science Lecture for Unit 26: Planetary Systems
- Topic area: Astronomy: Solar System
- Terms and concepts to know: Sun, planets, moons, asteroids, comets, jovian planet, terrestrial planet, planetary atmosphere, planetary rings, Red spot
- See historical period(s): Scientific Revolution , Renaissance (Copernicus)
The Solar System
Our science goal this week is to cover the basics of the modern view of the solar system. There is a ton of information available, so that's a pretty tall order. Our current view of the solar system (except for determining orbits) is largely the product of unmanned space vehicles. From the early 1960s when the first Ranger and Surveyor craft were flung at the moon and inner planets, through the heady days of Voyager and Viking (I worked at JPL during Viking and Voyager and they were heady days), up to the current missions of Cassini and Mars Pathfinder, the world's scientists have been collecting detailed information on the composition of planetary atmospheres, the size and shape of magnetic fields, the details of surface structures, and the lack of any conclusive sign of life other than on earth.
You may use an encyclopedia or any of the many excellent web sites or astronomy textbooks available to get the following information. If you are stuck, a good source is
Regardless of which site you use, start with introductory material on on the sun, and check out sections or links on sunspots. Study the introductory pages on each of the planets, and also on comets and asteroids.
There is a lot of material at this site. The outline below is a suggestion for organizing your notes.
- Classes and types of objects in the solar system
- Minor objects
- Composition and structure, size
- Source of energy, age
- Position and movement with respect to the galaxy
- Solar spot activity (because Galileo observed it--there are many other solar phenomenon of equal interest: solar flares, coronal behavior)
- Planets: major bodies
- Terrestrial planets are rocky, with substantial atmospheres
- Mercury: closest to sun, hot, rare atmosphere
- Venus: heavy atmosphere with greenhouse effect, very hot
- Earth: only planet with surface water in liquid state, oxygen/nitrogen atmosphere
- Mars: similar to earth; signs of water erosion, volcanic activity
- Jovian planets are gas giants, mostly hydrogen and helium, with no solid surface
- Jupiter: most massive object, largest object (besides sun), Red Spot, moons interesting (Io has volcanoes)
- Saturn: second to Jupiter is size; less dense than water, surrounded by spectacular ring system.
- Uranus: tilted on axis nearly 90 degrees--interesting currents
- Neptune: has spot similar to Red Spot on Jupiter
- Pluto: the anomaly, rocky twin object with Charon, orbit at angle to the plane containing the other planets; orbit intersects with Neptune. No longer considered a planet!
- Minor bodies
- Moons of planets: rocky, few with atmospheres, range in size. Titan has an atmosphere, Io has volcanoes, some other moons show evidence of having once had surface water.
- Asteroids: solar system debris? small, rocky bodies, different groups at different orbits from the sun
- Comets: ice and stone from far out beyond Pluto; two tails
- Origin of solar system: is planet formation normal part of star formation?
- All planets have mass, and the size of that mass determines other characteristics, such as whether the planet has an atmosphere. What other basic characteristics to all planets (and maybe their moons!) share? How do differences in the size or amount of these characteristics cause differences in other aspects of the planet? For example -- how do atmospheres vary with the mass and surface temperatures of the planet?
- Can we induce some general statements about planets from the common characteristics we've identified? What status do these statements have? Are they hypotheses to be tested? Theories? Laws?
Further Study/On Your Own
- Strobel's astronomy course also has a chapter on the solar system which is very good.
- You may want to look at the truly stunning multi-media astronomy hyper-textbook The Nine Planets from Bill Arnett, who teaches at the University of Indiana. Warning: This site is sponsored by advertisements, so it can be more distracting and difficult to navigate if you click on an advertisement link.
- Current results of the Mars Pathfinder mission are posted daily at JPL. This small roving unmanned exploration vehicle landed on Mars on July 4, 1997--with well over 5 million Web viewers watching (not to mention TV coverage). JPL also maintains a web-accessible archive of its best pictures from 25 years of planetary expeditions, including photos of asteroids and comets. The site is organized by both object and mission.
- If you want to see the current positions of the planets, look them up on the online orrery!
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