Thursday, September 24, 2009

A Jupiter Enticement

In an effort to encourage the growth of amateur planetary astronomy, I thought I would try to inspire you with a just a taste of the neat things that are possible for the amateur with decent equipment, careful planning and a bit of patience. A planetary astronomer is one who concentrates their observing efforts on bodies orbiting within our solar system. And of the easily visible planetary bodies, one of the most consistently satisfying, if not the most satisfying, is Jupiter.

If you look up into a clear night sky, you can see the planet Jupiter. After Earth’s moon, Venus and sometimes Mars, it is the brightest object in the heavens. It looks like a very bright object but it doesn’t twinkle like a star. It has a bright, steady glow.

Because Jupiter can be seen from Earth, people have observed it for thousands of years. Ancient civilizations had no way of knowing that they were really looking at a planet, but they knew that it was different from the stars. They knew it was different because, unlike the stars, it seemed to move across the sky in a unique way. In fact, the word “planet” comes from the Greek word for “wanderer.”

The planet is named for the king of the gods in the Roman pantheon. Also called Jove, but known to the Greeks as Zeus, he overthrew his father Saturn (in Greek, Cronus). He then drew lots with his brothers Poseidon and Hades to determine who would be the supreme ruler of the gods. Jupiter won the draw and became the ruler of Olympus and the patron of the ancient Roman state. Jupiter was the rain god and lord of the sky. His weapon is a thunderbolt which he hurls at those who displease him. He is married to Hera, but is famous for his many affairs. He is also known to punish those that lie or break oaths.

It was not until the invention of the telescope in the early 1600s that people were able to take a closer look at Jupiter. When the Italian astronomer Galileo Galilei turned his homemade telescope toward Jupiter in 1610, he saw a huge striped world with moons of its own. However, not much else was discovered about the giant mysterious planet for hundreds of years.

In the 1970s, the Pioneer spacecraft were sent to Jupiter. There were soon followed by the two Voyager missions an eventually by Galileo, the spacecraft named after the astronomer, which was launched in 1989 and which plunged into Jupiter’s atmosphere at the conclusion of the mission in 2003.

What has been learned about the planet from these missions is truly amazing. Jupiter isn’t a planet as we normally think of one—it’s actually a giant ball made completely, or almost completely, of liquid and gas. It has more moons than any other planet and is often viewed as its own mini solar system. The size of the planet is astounding, encompassing two-thirds of all the planetary mass in the solar system.

The environment of Jupiter is one of powerful storms, incredible lightning, deadly radiation, and winds many times faster than those of the strongest hurricanes on Earth. Scientists continue to be fascinated by the planet.

However, it is not just the planet that interest scientists and astronomers today. The moons, or satellites, of Jupiter are also subjects of intense study. And with forty-nine moons officially named so far, there is a lot to be learned.

Lately, much attention has been focused on the fact that liquid water has been detected on several of Jupiter’s moons, suggesting that the moons may once have had, or may currently have, some form of life since water is necessary for life as we know it. Europa, the sixth moon from Jupiter, is considered by many to be, along with Mars, among the likeliest places outside of Earth to find evidence of life.

We are just over halfway through Jupiter’s current apparition, which is a fancy way of saying the current appearance of Jupiter from its last Solar conjunction until its next conjunction. Jupiter's last Solar conjunction was January 24, 2009, and it was at opposition (opposite from the Sun in our sky) on August 14. It will next be in conjunction on February 28, 2010. This means that Jupiter is past its visual prime for this time around, but it is still a sight to behold for those who take the time and make the effort.

Some of those who make this effort are the members of the Association of Lunar and Planetary Observers, the A.L.P.O. This international organization studies the Sun, Moon and the solar systems planets, asteroids, meteors, comets. The goals of the A.L.P.O. are to stimulate, coordinate, and generally promote the study of these bodies using methods and instruments that are available within the communities of both amateur and professional astronomers. Incidentally, if you happen to speak with a member of the A.L.P.O., you would do well not to make humorous references to a certain brand of dog food. I mention this for your own good…

A.L.P.O. members are encouraged to submit their observations for comparison and study. The most interesting are regularly published for the benefit of the members and the general public. The Jupiter observations appear in the weekly Jupiter Newsletter. This electronic publication is edited and posted by my good friend and fellow amateur Craig MacDougal, who is an Assistant Coordinator for the Jupiter Section of the A.L.P.O. The Jupiter Newsletter may be found on the A.L.P.O. Jupiter Section page ( The newsletter link is located near the bottom of the page and is appropriately called "The ALPO Jupiter Newsletter."

And while you are on the Jupiter Section site, if you really want to get an idea of what is possible for the amateur observer, I encourage you to check out the link at the top of the page called "Jupiter Observations and Alerts." Within it you will find a wonderful sampling of images from various member observers stretching from 2007 back to 2005. You will see fine examples of digital imaging and pencil drawing--yes, people still do that.

I’m afraid that is all I have for now, but we will revisit the Jupiter system soon. To learn more about Jupiter and Jupiter observing, please check out these sites:

The Galileo mission home page

The Jupiter page of NASA/JPL's Solar System Exploration site:

A.L.P.O Official Site

A.L.P.O. Jupiter Section

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