By Jim Kaler

Go outside the next clear night to look for two bright planets. You don't need to know anything about astronomy to find them. As twilight darkens the western sky, Venus glows brilliantly and simply can't be missed. So lovely is its light that in ancient times it was named for the goddess of love and beauty. For the next few months it will continue to brighten. Near maximum it's easily visible in daytime and in a dark location casts eerie shadows. Closer to the Sun than Earth, as it orbits it goes through phases like the Moon, showing different portions of its day and nighttime sides. Discovered by Galileo around 1610, the phases were instrumental in proving that Copernicus was right, that the planets go around the Sun rather than the Earth.

On the other side of the sky, as darkness deepens, Jupiter rises high in the east. Though not as bright as Venus, it overwhelms anything else and is impossible to miss. Five time farther than Earth from the Sun, the king of the gods takes a dozen years to go around the sky against the background of the constellations of the Zodiac, residing in a different one each year. Looking through his small telescope, Galileo found four satellites that orbited in mere days, and drew the conclusion that if Jupiter could control its moons then the Sun could control its planets, again supporting Copernicus.

Venus and Jupiter could not be more different. Made of rock and iron like Earth but just a bit smaller and less massive, Venus displays a featureless cloudy surface. Not lovely at all, its clouds are made of sulfuric acid floating in a dense atmosphere composed mostly of carbon dioxide, the surface air pressure 100 times that on Earth. With a greenhouse effect gone mad, the temperature on the ground closes in on 900 degrees F. Radar observations show great numbers of volcanoes, though we don't know if any are active. The planet takes 243 days to rotate relative to the stars: backwards!

Jupiter is not a lot better. The largest planet in the solar system, 11 times Earth's diameter, 300 times Earth's mass, Jupiter is made mostly of hydrogen and helium, much like the Sun. Floating in this gaseous mix are clouds composed of ammonia and various hydrocarbons. Not far below the apparent surface, under crushing gravity the hydrogen turns liquid and then metallic. Rotating in just 10 hours, the planet has a powerful magnetic field and lethal radiation belts. Stretching out from the Jupiter are the four Galilean satellites, which are bright enough to be seen in binoculars. Heated by tidal stretching, Io, the size of our Moon, is the most volcanic body known. Europa may have a deep underground ocean. Made mostly of ice, Ganymede, the size of Mercury, is the solar system's biggest moon, while similar Callisto is not much smaller. Go take a look, then watch the planets change positions as the seasons progress.

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Copyright © James B. Kaler, all rights reserved. These contents are the property of the author and may not be reproduced in whole or in part without the author's consent except in fair use for educational purposes. First published in the January-March 2015 Clark-Lindsey Village Voice.