Night Flight to the Stars
Activity 4D: The Case of the Disappearing Rings
The famous ringed planet Saturn appears almost ringless for much of 1995 and early 1996. Every 15 years the Earth passes through the ring plane of Saturn and the planet's thin rings seem to disappear. The rings were edge-on in May and August of 1995 and have a slight tilt in the Fall.
Compare the two Hubble Space Telescope photographs of Saturn. In Dec. 1994, the Earth was above the lit face of the rings. The rings are seen edge-on in May, 1995. Saturn's moons Tethys and Dione can be seen in the ring plane to the left of Saturn.
Saturn's rings are composed of billions of particles--largely water ice--that range in size from tiny crystals to chunks the size of houses and school buses. Considering what the rings are made of and their size as shown above, predict how much lower the infrared brightness of Saturn will be in October 1995--compared with a ready when the rings were fully displayed. Record any reports about Saturn's brightness from the KAO astronomers.
Still more exciting is the opportunity to find and study Saturn's large moon Titan. Titan is almost as large as Ganymede and Callisto of the Jupiter system. The cooler Titan, however, has an atmosphere, mostly of nitrogen with various hydrocarbons mixed in. (The Earth's atmosphere is also predominantly nitrogen.) Titan's atmosphere is so thick that the Voyager spacecraft flying by Saturn could not see Titan's surface. Liquid ammonia and natural gas could exist on Titan.
At the time of the KAO observations, Titan will be 3 arc minutes west of Saturn. Saturn's rings will be 43 arc seconds in diameter and the planet will be 19 arc seconds wide.
This page was created by Daniel Helfman, a junior at Mission San Jose
High School in Fremont, CA.