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CHESHIRESTARWATCH |
by Jim Maynard
Star date:
05:05:97
Jupiter is the king of the planets. The Romans applied this name to this bright dot in the sky, the largest planet in our solar system. The four largest planets, Jupiter, Saturn, Uranus, and Neptune are sometimes called the Jovian planets.
These worlds are largely gases; hydrogen and helium (like our Sun), plus methane, water vapor, and ammonia. Any rocky core must lie far beneath the gaseous atmosphere we see. Below this lies a layer of liquid hydrogen, with metallic hydrogen near it's core.
Jupiter is 11 times the diameter of Earth and has a mass 317 times that of Earth. The temperature at the top of the cloud layer is -120 degrees (-180 degrees F).
Jupiter rotates on it's axis every 10 hours, meaning it's "day" is only about 40 percent the length of a day on Earth. This rapid rotation, combined with Jupiter's large size and fluid composition, makes it seem flattened at the poles.
The magnetic belts of
Jupiter are the strongest in the solar system. They trap particles coming
in from the sun and develop intense radiation belts around the planet.
The first two spacecrafts to voyage the 600 million kilometers (375 million miles) from Earth to Jupiter were Pioneer 10 and 11 in the mid-1970's. Much more informative were Voyager 1, which reached Jupiter in March 1979 (discovering the rings of Jupiter,
100 times dimmer than the rings of Saturn), and Voyager 2, which passed the planet in July 1979.
The latest robot probe to reach Jupiter is named Galileo. It arrived in December 1995, dropping the first probe into the upper reaches of the Jovian atmosphere Dec. 7.
First discovered by Galileo Galilei during the "99 years of astronomy" (1543-1642) the four largest moons of Jupiter are lively and full of surprises. Io (pronounced Ee-oo) is a world of active volcanoes, spewing sulfur dioxide, which create glow in the dark volcanoes. Io also lies well within the radiation belt of Jupiter, and the Galileo probe caught a volcano there in the process of erupting, throwing sulfur dioxide 63 miles above the surface of Io.
The Galileo spacecraft has returned stunning images and data from this frozen world. It is now known that Europa contains all the ingredients needed for life (although not life itself as far as we know) including a liquid ocean, and NASA has hastily planned a probe to travel to Europa to explore the depths of its waters. This probe will be tested in the frigid wastes of Antarctica.
Jupiter rises over the horizon at about 2:30 in the morning, in the east-southeast sky, and will be well placed in the evening sky by the end of July.
Clear skies and good viewing.
Jim Maynard is the head of the astronomy department at Earth Treasures and has been an amateur astronomer for more than 20 years. He is an astronomy student at Keene State College and leads star parties at Wheelock Park in Keene, NH.
If you have questions about astronomy or star gazing, call him at 603-357-7192.
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