The Jovian System - Techniques for Observing and Analyzing Orbits
- Explore, Discover, Observe
Hundreds of years ago Galileo pointed a very simple telescope toward the planet Jupiter. He was amazed that the little dots of light near Jupiter seemed to move back and forth in an organized way. Later mathematicians like Kepler and physicists like Newton used observations of planets and moons to describe laws and develop theories of gravity and motion. With our own telescope observations we will collect and analyze data so we can retrace Galileo's steps and the thinking of Kepler and Newton. The steps you use in this activity to understand the orbits of Jupiter's moons can be used for any planet.
Students worldwide have been watching and collecting data about Jupiter. You will be able to work with this data to map out the orbital periods and speeds of Jupiter's moons. You also might collect your own data or request images to carry out your own research. The process simply is to look at and collect data from images of Jupiter and its moons. You record the time and position of the moons as they move about Jupiter. If a moon reaches what appears to be an extreme position relative to Jupiter, that is called elongation, then you can determine the radius of the moon's orbit. Next, you record the position and the time for any moon of Jupiter, and given it's orbital radius, you can use geometry to figure out approximately what it's orbital period might be. If you know the size of Jupiter in miles or kilometers, you can figure out the speed of the moons as they orbit Jupiter.
Request and/or download images of Jupiter and its moons, especially if the images taken in a time sequence. Use webpages to look up the moons that are in the images. Use image processing tools to display and analyze the images. Make a composite image showing multiple positions of the moons over the time sequence. Print out this image and use it along with some geometry to calculate the period and speed of the moon. If you know the diameter of Jupiter you can change this speed into km/time or miles/time. Then you could ultimately calculate the mass of Jupiter by applying Newton's laws. There are resources to help you and several slide shows that illustrate the steps outlined in the activites. Check out the EDO - Orbits nexus community to find the slideshows
Real World Relevance
Trying to figure something
out about a system that you can see but not physically touch or go there is a challenge in astronomy and other sciences too. In this project, you will lean to interpret data in images to figure things out about Jupiter and its moons.
Culminating Event or Product
Students will be able to determine orbits of Jupiter's moons, both the period of the orbit and the speed of the moons in orbit. If they complete such activities with all four moons, they could see an example of how Kepler's Laws work and/or derive these laws for themselves.
Teacher Insights And Reflections
One nice result of completing these projects is that students learn to change their perspective when analyzing images. The perspective changes from looking at Jupiter and its moons from an 'edge on' perspective from our vantage point on Earth, to imagining a perspective from above in creating their interpretation and model of what the data represents.