Northern Illinois University
Department of Physics
College of Liberal Arts and Sciences

Saturn is the 6th plant from the sun and the second largest planet in the solar system. It is very bright in the night sky, and its rings are readily visible with a telescope. Saturn's rings are typically the focus of an observational project for the planet.

The rings of Saturn are vast belts of broken ice which encircle the planet in distinct bands. There are many different bands of rings which are categorized by astronomers into distinct sets classified by a capital letter. Currently there are A through F rings.

It is doubtful that the separation between the rings (tracks in the rings usually cut by what are known as "Shepherd moons") will be visible from Earth with our facilities. However, the separation between the planet and the rings should be discernable under good conditions. This separation represents the inner limit at which the gravitational attraction by the planet is too strong for stable, long-term rings to exist. This is known as Roche's Limit, and a brief discussion on the calculations involved is given below.

For this project, a minimal number of observing sessions will be involved, but the length of these sessions may be longer than others due to the number of different Saturn pictures desired.

Procedure

1. Locate Saturn in the telescope at Davis Hall.
2. With the observatory manager's assistance, attach either a camera or the CCD to the scope.
3. Capture at least one image, or more if you choose. Try several different images in different scopes and powers of magnification. Choose which image gives the sharpest definition of the rings about the planet.
4. With use of photography, or with the CCD images, the pictures may be enlarged so that measurements may be easier to make.
5. Alert observers may be able to pick out moons of Saturn, specifically Titan and Rhea, if you look closely. Sky and Telescope will show where Saturn's moons should be in relation to the planet. Ambitious observers can attempt to perform an evaluation of the moons as per the Jupiter project.

Measuring the Rings and Roche's Limit

Using the given diameter, you can measure by direct ratio the size of the rings to the diameter of the planet. This is easily done via the pictures you will take and a ruler. A more precise method is to enlarge the images and try to measure the gap between the planet and rings, which should correspond to Roche's limit. Also measure the maximum visible width of the rings, and look for any possible divisions between the rings. With the CCD images, it may be possible to distinguish Cassini's division, which is the most visible gap in the rings, as well as banding on the planet's atmosphere. If these phenomena are visible, note it in your report. Measure distances of these as well or, in the case of the bands, the width of them and the portion of the planet's atmosphere they take up. Be sure to explain what you see.