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King of Planets

+ Von Del Chamberlain +

People are out looking around the night sky a lot these days. "What is that bright star in the sky?" many have asked me. Before I answer, I must ask a question of my own. "What time of night are you referring to?" Usually the answer is, "Evening, just after dark." Then I need to ask, "What portion of the sky?" Depending upon the current configuration of the planets I can often answer "Jupiter".

Jupiter has always been one of the dominant objects of Earth's sky for human eyes. Although the ancients had no way of knowing that this was the largest of the planets, they named it well. In their minds, the hurler of thunderbolts looked down from lofty Mount Olympus, so it seemed appropriate to associate him with the great luminary looking down from heaven, nearly always visible, and always brilliant. The planet only disappears for a couple of months when it is lost in the glare of the Sun, being on the far side of its orbit as we view it.

There are many things the old Greeks did not know about this great light of heaven, but the more we study it the more appropriate it seems that they named it as they did. Jupiter has a diameter about 12 times that of Earth, yet it rotates on its axis more than twice while Earth rotates once. Jupiter has nearly 318 times more mass than Earth: indeed nearly three times more mass than all the other planets combined. Except for the Sun itself, Jupiter is the giant of the Solar System. It is nearly large enough to have become a star. Think about that. If Jupiter had been a bit more massive we would be living in a binary star system. Or would we? If Jupiter had become a star, would life have been possible on Earth? Probably so, for Jupiter would have been a dim star, orbiting 5 times farther out from the Sun than Earth is. For us, its distance constantly changes between 4 and 6 times the solar distance. As Earth sweeps between Jupiter and the Sun it is 4 times farther away than the Sun, and when Jupiter is beyond the Sun, on the far side of its orbit it is 6 times farther from us than the Sun. Thus, if Jupiter had been a star, orbiting just as it currently does, it would be an extremely bright, but constantly changing, light. How different things would be. We would not have had nearly as much darkness, for whenever Jupiter would be in the sky it would cast its much greater brilliance into our otherwise night--far more light than the full moon we know. The famous science fiction author, Arthur C. Clarke, included the idea of Jupiter becoming a star in his series of books, 2001, 2010, 2061, and 3001.

Although Jupiter does not truly rule the Solar System, for that is the role of the Sun, it does have a family of its own. At least count we know of sixteen natural satellites orbiting Jupiter. None of these were known to the Greeks, for telescopes were required to see them, but as soon as Galileo looked at Jupiter through his lenses in 1610 he discovered four tiny dots accompanying the planet. That was all for the better part of 300 years, but as telescopes became better and bigger, another Jovian satellite was found in 1892. Additional ones were discovered in 1904, 1905, 1908, and 1914. A pair of them were added to our awareness in 1938, then another in 1951. Space science technologies discovered one in 1974 and three more in 1979. Now, we have seen these members of the Jovian family in some detail through the eyes of space probes, and they are among the most astonishing worlds we have ever seen. Each and every one of them is unique, crying out for further exploration. In addition to these larger bodies, we have learned through space programs that Jupiter sports a ring composed of tiny orbiting particles.

I can only hope that you will go out and locate Jupiter. You will know it when you see this eye-dazzler, and once you have found it you can follow it for the rest of your life. As you enjoy it, think about its role in ancient history; consider how much we have learned about it; then contemplate the many secrets it still holds for future discovery through exploration.

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