Plenty of Planetary Pleasures

By now I hope you have visited Seagrave Observatory in North Scituate or Ladd Observatory in Providence to observe the magnificent ringed planet Saturn. For a two-week run in mid-April the seeing was absolutely astounding. In fact, many Skyscraper members commented they hadn't seen such detail in quite some time. Several divisions could be seen in Saturn's system of rings, and five of his largest moons were usually visible. And the disk of the planet revealed more subtle colors and structure than we can ever remember seeing in recent years.

When Jupiter rose out of the turbulence and sky pollution to the east, similar great views of this giant planet greeted our eyes! And now, through much of the summer, Jupiter will be well placed for observing. Jupiter, only 500,000,000 miles from us, shows a wealth of detail to a patient observer, especially if you know what to look for. Following is a beginner's guide to observing this system of worlds that behaves like a miniature solar system.

First you have to know where to find Jupiter in the sky. During early June, Jupiter is the bright object you'll see when looking south and about half-way up from the horizon just after sunset. It resides among the not well recognized stars of the constellation Virgo. I realize that Jupiter requires a telescope to really appreciate its beauty, but if you have a pair of 10 X 50 binoculars, train them on Jupiter and you can spot some of his brighter moons.

But the best way to view Jupiter is through a telescope, whether it is a small backyard instrument or one at the local observatories. My favorite turn-of- the-twentieth-century author, Garrett P. Serviss called Jupiter "one of the greatest pleasures that the telescope affords." One of the first things that will catch your eye will be the Galilean moons. Galileo Galilei first observed them and Jupiter in 1610, so now the four moons collectively honor his discovery. They are: Io, Europa, Ganymede and Callisto.

If you want to identify which moon is which, I suggest you visit the following web site and download the Galilean Satellites program: http://www.cox-internet.com/ast305/dansoftware.html. It displays the relative positions of the Galilean moons for a given date and time. While these satellites parade around Jupiter in the plane of its equator, many interesting events occur for us earth-bound astronomers to observe.

When a moon passes in front of Jupiter, casting its shadow onto the Jovian cloud tops, it is called a transit. Besides seeing the satellite's shadow, you may also see the bright disk of the satellite traversing Jupiter's clouds at the same time, though this event is more difficult to observe. A moon may also pass behind the planet. That's called an occultation. Jupiter's shadow can even eclipse a satellite as well; gradually the moon will either blink out or reappear. Also, it's fun to watch all four moons line up on one side of the planet. As you can see there's much to observe in Jupiter's vicinity. Accurate predictions (to within one minute) of these events can also be calculated using software found at the above noted web site as well.

In addition, you'll easily notice the more prominent dark bands or belts in Jupiter's cloud tops. The once dominant feature of Jupiter (from at least Galileo's time thru the mid 1970's) was the famous Great Red Spot. It is nothing more than a giant storm in Jupiter's clouds that has been active for more than 400 years. Unfortunately it's not as red or great as it once was, so it might be difficult to detect in smaller instruments without special filters to enhance the image. Today it could be called the Not So Great Beige Spot! The web-site already mentioned above also offers software that predicts when the Great Red Spot will be visible.

Keep in mind that Jupiter rotates once in 10 hours, making it possible to see the entire planet in one or two nights of observing. Also, even under low magnification the view will be rewarding. For example, 36 power will make Jupiter appear as large as the full moon does to the naked eye.

So get out there with your telescopes and view some of our solar system's most beautiful planets. Then continue exploring the rest of the universe. You've got a lifetime of discoveries awaiting you every clear night.

If you don't have access to a telescope or you'd like to explore the universe with larger instruments, then by all means visit Seagrave Memorial Observatory on Peeptoad Road in North Scituate. We offer public viewing free of charge every clear Saturday night. We open the gate to our facility about a half-hour after sunset. Our members will be happy to share their love of the sky with you. More information, including directions and membership, can be found at our website: www.theskyscrapers.org.

As always, keep your eyes to the skies.