The word planet came from the Greek word "planetes," which means "wanderer." Since the dawn of civilization, stargazers, astrologers as they were once called, have observed the nighttime sky and noticed bright objects travelling along the same path in the sky as the Sun and Moon. The stargazers found that the objects did not twinkle like ordinary stars. These early scientists reasoned and also saw that the objects were bright and were close to Earth. Henceforth, the Greeks honored the original name and shortened it with the name, "planets."

 

There are five known planets that can be seen in the night sky. Mercury, closest planet to the sun can be seen after sunset and before sunrise. Venus, closest planet to Earth, can be viewed as the morning or evening star, depending on its position in its orbit around the sun. Further out, about one and a half times the distance our Earth is to the sun, the red planet Mars is visible. Beyond Mars lies the asteroid belt, with its largest object, Ceres. This object, which orbits between Mars and Jupiter, was reclassified back in the 1800's as an asteroid. In August of 2006, Ceres was reclassified again as a Dwarf Planet. Jupiter, which covers one constellation of the zodiac a year, orbits outside of the asteroid belt. The last of the naked-eye planets is the ringed planet Saturn.

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It should be noted that a "perturbation" is a deviation in a system, moving object, or process from its regular or normal state of path, caused by an outside influence.

On March 13, 1781, William Herschel discovered such perturbations in Saturn's orbit. Herschel used these findings to predict the existence of a planet beyond Saturn. This new world, named Uranus after the Greek god of the sky, was found in the constellation of Taurus. On September 23, 1846, Johann Gottfried Galle noticed the very same perturbations in Uranus's orbit. This led to the discovery of Neptune in the constellation of Aquarius.

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In the early 1900's, an astronomer named Percival Lowell noted perturbations in Neptune's orbit. This led to the discovery of the mysterious "Planet X." Throughout most of his life, Lowell was determined to find this mysterious world beyond Neptune, the planet named for the Roman God of the Sea. After checking the sky for several years, Lowell died before the discovery was made....

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​The alignment of the naked eye planets on April 25, 2002.

Planetary Conjunction of 2002, Courtesy of Stellarium Computer Program