Saturn is one of the favorite objects of astronomers. It has been viewed and imaged millions of times. The Cassini-Huygens spacecraft orbits Saturn and returns images of the rings, moons, and moonlets. Operated at Saturn since July 2004, Cassini yields views of the fine structure details of the rings.
I discovered another very strange wonder, which I should like to make known to their Highnesses . . . , keeping it secret, however, until the time when my work is published . . . . the star of Saturn is not a single star, but is a composite of three, which almost touch each other, never change or move relative to each other, and are arranged in a row along the zodiac, the middle one being three times larger than the lateral ones, and they are situated in this form: oOo.
Saturn takes about 30 yrs to orbit the Sun. The plane of the rings is tilted with respect to the plane of the orbit. From our orbit closer to the Sun, our view of the rings varies over time as illustrated in this graphic. Sometimes we see the rings from above, sometimes below, and sometimes they are edge on to us and not visible. The edge on views are the equinoxes of Saturn seen every 15 yrs.
Cassini completed the primary mission exploring the Saturn System in June 2008. The mission was extended to September 2010. The spacecraft is now in a second extended mission called the Cassini Solstice Mission which goes through September 2017.
Cassini has helped confirm the orbits of 62 moons of Saturn. Among many wonderful discoveries over the years about those moons, Cassini has looped close by the ring system many times and viewed them from many different vantage points. Some views were from afar and some extremely close. This image in silhouette revealed some previously unknown faint rings.
Some of the most interesting views of the rings have come during the times near equinox when the rings are illuminated at their edge. They are less visible to us from our Earth view at that time. But, Cassini is close enough to still capture their details. In these close and detailed views, there are some surprising features of shadows cast across the ring plane by small shepherd moons, moonlets, and by piles of ice in a ring. Shepherd moons clear gaps between rings and bring stray ice chunks back into rings by gravitational interactions. The fine structures of the rings look like the tiny grooves of a phonograph record. Here are some beautiful examples.
This 53 sec video shows the outer F-ring orbiting Saturn. At the 34 sec mark, watch the two shepherd moons come around the orbit. Their action as a pair keeps the smaller particles of the F-ring in a tightly confined narrow band.
The Cassini-Huygens Mission is a resounding success. Cassini will continue returning data until September 2017. Tens of thousands of images have been obtained. You can browse them at this convenient web site called CICLOPS – Cassini Imaging Central Laboratory for Operations. Or, use this search page. Type in a keyword or two and click search. Try ‘pandora’. Click on any of the results.