The Pleasures of Jupiter

If you haven't had the opportunity to observe Saturn through any of the local observatory telescopes these last few months, you're out of luck until mid- January 2007. That's the next time this magnificently ringed world will once again clear the eastern tree-tops at a reasonable hour (before midnight) at these facilities.

However, we are fortunate that Jupiter has now become the showpiece of the heavens from both Seagrave Observatory in North Scituate and Ladd Observatory in Providence. Though Saturn's rings were the main attraction for our guests to observe on any public open night, Jupiter, being much closer to the Earth, shows a lot more detail to even an inexperienced observer. Plus, if you know what to look for, the Jovian system and its four prominent moons present many interesting events to enjoy. So before you visit your local observatory, learn about the dynamic and ever changing system of Jupiter and his moons.

When Jupiter finally rose out of the turbulence and sky pollution to the east, we were treated to great views of this giant planet. And now, through much of the summer, Jupiter will be well placed for observing. Following is a beginner's guide to observing this system of worlds that behaves like a miniature solar system.

Since this column is scheduled to appear in July, finding Jupiter in the sky will be quite an easy task. Within 15 to 20 minutes after sunset, you shouldn't have any trouble locating brilliant Jupiter due south of your location and about halfway up off the southern horizon. It will be the brightest object in the sky in that direction, except when the First Quarter Moon passes just 5 « degrees below it on July 3!

I realize Jupiter requires a telescope to really appreciate its beauty, but if you have a pair of 10 X 50 binoculars you can at least 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 Jupiter's four brightest moons. Galileo Galilei first observed them and Jupiter in 1610, so they are now known as the Galilean Satellites in his honor. They are: Io, Europa, Ganymede and Callisto.

If you want to identify the Jovian moons, I suggest you visit the following web site and download the Galilean Satellites program: http://members.cox.net/astro7/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 and casts a 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, which is 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.

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 1970s) 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 the storm'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. (The Dan's Software web-site also offers software that predicts when the Great Red Spot will be visible.) In recent years the red coloration has come back somewhat, making the Great Red Spot a little easier to see than it had been for 15 years or so.

Did you know Jupiter has a new "little red spot" that has recently formed? It's called "Red Jr." This new spot formed from the merging of three white spots in recent years. However, more recently it has turned red, much like its bigger brother, "Red Sr." It will be very interesting to witness the evolution of this new feature in the Jovian cloud tops.

As I was writing this column, an announcement was made that on July 4th, Red Jr. would slide past the Great Red Spot. (These huge storms reside at different latitudes in Jupiter's cloud tops; therefore they rotate around the planet at different rates, which allows features to pass one another form time to time.) Contrary to some media reports, the two spots will not collide. The outer fringes of these storms will most likely interact, though astronomers do not expect any significant changes. There is some speculation that Red Jr. may lose energy and its red coloration may disappear as a consequence. If you don't have access to a telescope, you may find an internet site or two that will display the event.

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. 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 if you own your own telescope get outside and view the fascinating system of Jupiter. 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

Furthermore, you can visit Ladd Observatory on the corner of Hope Street and Doyle Avenue on Providence's East Side every clear Tuesday night. The doors open at 8:30 pm during the summer months and admission is free. More information can be found at Ladd's website: www.physics.brown.edu/physics/commonpages/ladd/

While outside during the summer months, don't forget to look skyward for a few shooting stars. You'll see five random meteors or so on any clear evening, but at the end of July, from the 28th through the 30th, there are two meteor showers that may enhance the number of meteors seen. The Moon, a few days from First Quarter, will not severely brighten the sky to overwhelm the visibility of these shooting stars. Most will be yellow in color, and a few may enter our atmosphere as bright exploding fireballs.

And finally, the Earth is at its farthest distance from the Sun this year on July 3 at 94,508,169 miles.

As always, keep your eyes to the skies.