Get Ready to Observe Saturn

Back in my February column I wrote about one of my favorite constellations, Orion. For April I thought I’d provide an observing guide to my second favorite planet, Saturn. Did it surprise you that this beautiful ringed-world placed second in my planetary favorites list? Well, for me Jupiter is my favorite because it is much closer and provides a larger image in a telescope, which allows much more detail to be observed. Besides, one can easily watch the bright Galilean satellites parade around massive Jupiter like a miniature solar system. And Jupiter’s cloud belts and zones are so much more prominent than Saturn’s.

April is a good time to feature Saturn because on the 3rd at around 7:44 pm EDT the planet is at opposition (opposite the Sun in our sky) and at its closet point to the Earth, approximately 800,714,857 miles! For you native Rhode Islanders that is farther than Newport!

While this guide is basically for owners of a telescope, it can also be referenced for those of you who may wish to visit one of the local observatories in the near future. More on that a little later.

Before we can observe Saturn we first must locate this planet among all the stars in the night sky. A couple of years ago Saturn was within the easily recognizable constellation of Leo. Now the sixth planet from the Sun has moved into Virgo, whose pattern of stars is not that remarkable. However, on April 1st Saturn rises around 7:00 pm DST (Daylight Saving Time) in the east. One and a half to two hours later he will be about 20 degrees above the east-south east horizon. It will be the brightest star-like object in the area, and it will have a yellowish hue to it.

If you cannot find Saturn at that time, wait until the night of April 16-17 when the almost Full Moon will pass beneath and to the right of Saturn by less than ten degrees (a fist held at arm’s length covers this distance).

Providing you own even a small telescope, you must try to focus in on this wonderful planet. The very first feature that will catch your eye is the rings, the beautiful attribute for which Saturn is most noted for. In astronomer Garrett P. Serviss’ 1901 book, Other Worlds, he wrote, “Many telescopic views in the heavens disappoint the beginner, but that of Saturn does not. Even though the planet may not look as large as he expects to see it from what he has been told of the magnifying power employed, the untrained observer is sure to be greatly impressed by the wonderful rings, suspended around it … No previous inspection of pictures of these rings can rob them of their effect upon the eye and the mind. They are overwhelming in their inimitable singularity, and leave every spectator truly amazed.”

During the span of Saturn’s almost 29½ year orbit of the Sun, our Earthly perspective affords us a view of this magnificently ringed world from different angles above or below the ring plane. Since September 2009 we have been observing the north face of the rings, which are now tilted less than 10 degrees to the horizontal. Despite this small angle, they remain quite visible through just about any telescope. This tilt will increase each year until 2017 when the rings will be at their widest angle of 27 degrees. Last year we observed the rings tilted only two to three degrees.  

It is amazing Saturn’s rings are visible at all, considering the planet’s distance from the Earth and the fact that the ring plane is only about 328 feet thick (just larger than the length of a football field). The rings are comprised of irregularly shaped dirty snowballs, ranging in size from grains of dust to many particles the size of pebbles. There are also some “boulders” as large as a car or small house-sized bodies. They all orbit Saturn along the planet’s equatorial plane.

While Saturn’s rings are slowly de-orbiting and will eventually all “rain” down onto his cloud tops (in 50 to 100 million years or so) and cease to exist, there’s no excuse, except for bad weather, not to catch a glimpse of Saturn with your own telescope or to visit one of the local observatories.

Once you tire of ring watching you can turn your attention to the disk of Saturn himself. The light-colored bands and zones in Saturn’s cloud tops are much less prominent than those of Jupiter. (Very little cloud detail can be seen in small telescopes.) However, bright “spots” do develop from time to time. As I write this column at the end of February, a very large bright feature, which had first developed during December 2009, was continuing to expand in Saturn’s North Temperate Zone. Do a Google search on the web to see if this so-called “Serpent Storm” persists. I have yet to view it with some larger telescopes.

In addition, both before and after opposition, one can observe the shadow of Saturn projected behind the planet and onto his rings. Also, as the observing angle of Sun/Earth/Saturn increases a keen-eyed observer should have no difficulty in detecting the shadow of the rings upon Saturn’s cloud tops. These particular viewing circumstances provide a stunning 3D effect of the Saturnian system.

In conclusion, locally you can also see about 1/8th of Saturn’s 61 moons, depending upon which size telescope is used. In order of size and brightness they are Titan, Rhea, Iapetus, Dione, Tethys, Enceladus, Mimas and Hyperion. The first five or six of the above can be observed in a dark moon-less sky using the 12-inch Brashear refractor at Ladd Observatory.

Hopefully by the beginning of April the snow will be gone and the temperature will be more comfortable for star and planet gazing. Drag those telescopes out of your basement, closet, or garage and put them to good use collecting the light of beautiful celestial objects.

But if you don’t have a telescope or the one you do own does not provide a great view of Saturn, I encourage you to visit one of the local observatories. I suggest waiting until mid-April to give Saturn ample time to rise higher into the sky and clear the local tree-lines and buildings. Check out the websites for Seagrave Memorial Observatory in North Scituate (http://www.theskyscrapers.org) or Ladd Observatory (http://www.brown.edu/Departments/Physics/Ladd/) in Providence for the public night schedule. The large telescopes at these two facilities will certainly reward you for your efforts.    

As always, keep your eyes to the skies.