Jimmy Westlake: Approaching giant
August 6, 2009
Steamboat Springs — What’s that really bright star shining in our midnight sky? It’s not a star at all – it’s the planet Jupiter, the largest planet in our solar system.
You might have noticed it rising over the southeastern mountains around 10 p.m. The gap between Earth and Jupiter has been closing during the past few months and the two planets will be as close together as possible on the night of Aug. 14, when they’ll be just 375 million miles apart. That’s the night of Jupiter’s opposition to the sun, when the Earth passes directly between the giant planet and the sun. Rising as the sun goes down, Jupiter will remain in the sky all night long, setting as the sun rises. After Aug. 14, Earth and Jupiter will grow farther apart. The planet then will be a constant companion in our evening sky throughout the remainder of the year, but it will not appear any bigger and brighter than it does for the next few weeks.
This year, Jupiter slowly is sliding westward each night, through the stars of Capricornus, the Sea Goat, just east of the misty star clouds of the Milky Way. The full moon will rise alongside Jupiter tonight.
If you own binoculars, try aiming them at Jupiter, and you might glimpse one or two of Jupiter’s four giant moons. A small telescope will show them even better. It’s fascinating to watch the moons dance around Jupiter, changing their positions each night.
Jupiter is a different kind of planet than Earth. It is a colossal ball of hydrogen and helium gas, held together by its enormous gravity. Jupiter has no solid surface to stand on. If you tried to land on it, you would just sink down into its deep atmosphere and eventually splash down into an ocean of liquid hydrogen, thousands of miles deep.
With your telescope, you can see alternating light and dark cloud stripes in Jupiter’s atmosphere, as well as its famous earth-sized storm, the Great Red Spot. Recently, a comet or asteroid crashed into Jupiter’s atmosphere and exploded with the energy of thousands of nuclear bombs. The explosion left a dark, sooty cloud that astronomers have been monitoring carefully to understand the nature of such events. This is a stark reminder that collisions do occur in our solar system and we shouldn’t think of ourselves as immune from similar impact events. Interesting, isn’t it, that by studying Jupiter and the other worlds in our solar system, we learn much about our own planet Earth?
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Spot Jupiter for yourself in the southeastern sky this month during the late evening.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. He is an avid astronomer whose photographs and articles have been published all around the world. His “Celestial News” column appears weekly in the Steamboat Today newspaper and his “Cosmic Moment” radio spots can be heard on local radio station KFMU. Also, check out Jimmy’s astrophotography Web site at http://www.jwestlake.com.