Bernie Badger: Rare alignment brightens Saturn's rings

Saturn is in opposition tonight, which is a great time to observe the most photogenic planet in the solar system. Opposition means that the sun and the planet are on opposite sides of the Earth. Saturn will just be getting high enough to see right about 9 p.m. tonight. The precise moment of opposition occurs at 9:22 p.m. , but any time tonight will be good.

To help celebrate, the Brevard Astronomical Society will be having a free star party in the parking lot outside the Eastern Florida State College planetarium and observatory in Cocoa. Many different sizes and styles of telescopes will be there, along with knowledgeable amateur astronomers to guide your viewing.

For a few hours around the exact moment of opposition, there is supposed to be a brightening of Saturn's rings, known as the opposition surge. This can be noticed by comparing the brightness of the rings with the planet's disk. The effect comes from the play of shadows within Saturn's rings. The rings appear solid but actually consist of clouds of ice particles orbiting independently.

Each particle is like a tiny moon. Like the moon, each has a phase that depends on our relative viewing angle. At opposition we are seeing the "full moon" view of the particle. The phase change provides only a gradual brightening without a sharp peak. The opposition surge comes from another source.

On rough surfaces on airless moons, there are tiny crevices, which are in shadow. When looking at the surface from the direction of illumination, all these shadows are hidden and you see to the bottom of the crevices. Our own moon brightens considerably when moving from 4 degrees to 0 degrees angle of incidence. Saturn's rings have just such a cumulative effect as each moonlet in the rings brightens.

I hope you are also watching Venus catching up with Jupiter over the next weeks. This is leading to a conjunction at the end of June.

Mr. Badger is Project Coordinator at the Eastern Florida State College Planetarium in Cocoa. Send questions, suggestions, or comments to badgerb@easternflorida.edu

At the planetarium

Friday

7 p.m.: The Planets

8:15 p.m.: Antarctica (IMAX)

9 p.m.: Led Zeppelin Laser Experience

Saturday

7 p.m.: Amazing Universe

8:15 p.m.: The Living Sea (IMAX)

9 p.m.: Pink Floyd "Dark Side of the Moon"

Wednesday

2 p.m.: The Cowboy Astronomer

3:15 p.m.: Whales (IMAX)