The last time the plane ring crossing was observed, in 1995, the Hubble Space Telescope captured the event.

In 1612, Italian physicist and astronomer Galileo Galilei observed the “ears” of Saturn disappearing. He didn’t know what was happened. He wrote, “Has Saturn swallowed his children?” However, the next year, they once again returned, but Galileo didn’t know why.

Several years later, in 1655, Dutch astronomer, mathematician, and physicist Christiaan Huygens suggested that the “ears” that Galileo described around Saturn were really a ring. In 1675 Italian-French astronomer Giovanni Cassini stated that Saturn’s ring was really several smaller rings with gaps between them. One gap was eventually named after Cassini.

Today, we know that as the planet Saturn orbits the Sun (it takes about 29.5 Earth years to make one orbit around) it periodically turns its rings “edge-on” to the Earth.

Thus, we are in the plane of the rings, rather than being above or below the plane. When this orientation happens, the very thin rings of Saturn almost disappear from our view.

The rings around Saturn are composed of various individual particles, or “moonlets,” that are as small as microscopic dust and as large as a school bus.

Astronomers think that the rings were formed from a violent collision of a comet or asteroid with an icy moon of Saturn. In fact, if all of the little moonlets were glued together into one big moon, astronomers estimate they would be about 1/20,000th the mass of Earth’s Moon or about the same mass of Janus, one of Saturn’s smallest moons.

The plane ring crossing is kinda like looking at an old vinyl phonograph record. It is easy to see when you look at the record from the top or from the bottom. It looks like a solid circle. However, when you look at a record from the side, it is only a narrow line, barely visible. It’s the same way with Saturn’s rings.

So, what will you find over the next months. Read on to see what you will observe with Saturn's rings from  April to September in 2008.