The planets Earth and Saturn are currently aligned in the same general direction from the Sun. April 28th was the date of the most direct alignment called opposition. Saturn was in the opposite direction of the Sun as viewed from Earth. Saturn rises in the east each evening at about the same time the Sun sets. By late evening it is positioned high and is a pleasing sight in a telescope.
I am fortunate to have an account with the University of Iowa’s Robotic Telescope called Rigel. It is located at the Winer Observatory near Sonoita in southern AZ. The children of the Rigel director were in my physics classes years ago. He kindly gives me the account for my use. On the night of May 4, the Rigel telescope obtained this image for me of the planet Saturn.
How cool is that? I got to use a telescope over a thousand miles away to get this image. What if I could use a spacecraft actually orbiting Saturn to see images up close and in great detail? I would want to see some of the fine structure details of the rings. Galileo called the rings ‘ears’ when he first saw them in 1610.
Saturn takes about 30 yrs to orbit the Sun. The plane of the rings are tilted with respect to the plane of the orbit. Our view of the rings over time varies 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. Those are the equinoxes of Saturn every 15 yrs.
Here is a beautiful collection of images taken over a 6 yr interval by Alan Friedman between 2004-2009. This image appeared on the Astronomy Picture of the Day.
In October 1997, the Cassini spacecraft was launched toward Saturn along with the European Space Agency’s Huygens probe. The probe studied Titan, Saturn’s largest moon. It landed on Titan’s surface on Jan. 14, 2005.
Cassini completed its 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. This mission goes through September 2017.
Among many wonderful discoveries over the years about the moons of Saturn, Cassini has looped by the ring system on many different occasions. The spacecraft has had many different vantage points of the rings. Some from afar and some extremely close. This image is Saturn in silhouette. It is one of the most dramatic views to date.
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 its images. In these close and detailed views, there are some surprising features of shadows cast across the ring plane by small shepherd moons 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. In addition, the fine structure of the rings reminds me of a phonograph record with the tiny grooves. Here are some interesting examples.
Here is a 53 sec video showing the outer F ring orbiting Saturn. At the 34 sec mark, watch the two shepherd moons come around doing their job.
The Cassini-Huygens Mission is a resounding success. Cassini has work to do for several more years. Tens of thousands of images and videos have been obtained. You can search them at this convenient web site called CICLOPS – Cassini Imaging Central Laboratory for Operations. Use this search page. Type in a keyword or two and click search. Try ‘pandora’. Click on the results.
My wish to use a spacecraft in orbit around Saturn to see the images of the rings up close is a reality. This is a remarkable thing. NASA and the ESA are two great partners in space exploration giving us all wonderful views of these worlds.
Thank you for joining me.