Pleasure at the Telescope: Observing Jupiter
April 2003 :
Note: This article may contain outdated information
This article was published in the April 2003 issue of The Skyscraper and likely contains some information that was pertinent only for that month. It is being provided here for historical reference only.
I can only hope that once astronomical spring arrived on March 20, the weather rapidly improved, providing ample opportunity to observe Saturn and his magnificent rings for at least another month or so before this beautiful planet disappears into the solar glare.
As I mentioned last month, we've been fortunate during the last few years to have Jupiter and Saturn prominently positioned in the early spring evening sky. This scenario will not always be the case. Even now the two planets are moving further apart in the sky. Eventually you won't be able to observe both on the same evening. Though that will be unfortunate for our annual spring star parties at local schools, there's always something interesting to observe in the heavens.
Where can you currently find Jupiter in the vault of the heavens? Jupiter is the brightest object high in the southern sky, residing within the indistinct constellation of Cancer the Crab. Although Cancer's star pattern is not very bright, there is one beautiful star cluster called the Beehive just less than two full moon diameters from Jupiter.
I realize that Saturn and Jupiter require a telescope to really appreciate their beauty. If you don't have access to one, try training a pair of 10 X 50 binoculars on these giant worlds. With Saturn's rings wide open, the binoculars should show you an oblong image, hinting at the ring system. Train them on Jupiter and you can spot some of Jupiter's moons.
You can look at the wonderful pictures of the planets in so-called coffee- table astronomy books, or I can describe in great detail my recollections of planetary views through a variety of telescopes both large and small. However, nothing can compare to your first glimpse of Jupiter or Saturn through even a small or modest telescope.
My favorite turn-of-the-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. When several of the Galilean moons are visible at the same time, they sometimes appear in a straight line, parading around Jupiter in the plane of its equator. This astrophysical arrangement presents many interesting events 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.
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) is 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. Today it could be called the Not So Great Beige Spot! Monthly magazines devoted to the astronomy hobby, like Sky and Telescope or Astronomy, will have specific times of events occurring in the Jovian environment.
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. Please note our new public open night schedule. Beginning in April, the observatory will once again be open every Saturday night, weather permitting of course. Our members will be happy to share their love of the sky with you. If substantial snow still covers our parking lot, the observatory will remain closed. More information, including directions, membership, and weather related closures can be found at our website: www.theskyscrapers.org
