Minnesota Starwatch

University of Minnesota

Department of Astronomy

Minnesota Starwatch for August 2004
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Starwatch Newsletter

Minnesota Starwatch is a newsletter describing the night sky in the Midwest.

It is updated monthly, and is produced by the
Department of Astronomy, University of Minnesota
116 Church Street SE, Minneapolis, MN 55455

Minnesota Starwatch for August 2004

This year, the Perseid meteor showers which will peak on August 11-12 occur when the Moon will be a late rising waning crescent, allowing good dark skies for meteor viewing. Go out after midnight or a few hours before dawn, let your eyes adapt to the dark, and enjoy the celestial show.

This month, new moon occurs on the 16th, with the full moon squeaking in on August 30. Venus blazes in the pre-dawn skies, while a fainter Saturn is a bit harder to pick out in the Gemini constellation. Jupiter is your best bet for evening viewing, although it will get considerably fainter as the month progresses. On August 18th, watch for the crescent moon passing just over 2 1/2 degrees from Jupiter.

Spectacular pictures came in last month from a spacecraft launch seven years ago, on October 15, 1997. A Titan 4B Centaur rocket started the Saturn Explorer Cassini on its 2.2 billion mile journey. The rings of Saturn have once again astonished us with their beauty and mystery. The Cassini Division is the large gap between the A and B rings, named for the French-Italian astronomer Jean-Dominique Cassini, who discovered this gap in 1675, and for whom the spacecraft is also named. Particles in the Cassini division appear to have higher concentrations of "dirt", darker material unlike the icy other rings. This dark material is very similar to that seen on Saturn's moon Phoebe, and gives rise to speculation that the breakup of a moon has spread its dirt into ring-like structures around Saturn. Although the particles that make up Saturn's rings are tiny, Cassini's detailed has found beautiful bunched up waves of these particles, like a series of traffic jams slowly making their way down a highway.

Twelve different instruments on the spacecraft study a wide variety of Saturnalia, including the composition of Saturn's atmosphere, the magnetic fields that sweep around the planet, and the properties of its many moons. In December, the Huygens probe will be dropped into the atmosphere of Titan, Saturn's largest moon, where it will parachute down to the surface, giving us our first views of this new world. It is named for the Dutch scientist Christiaan Huygens, who solved the puzzle posed by Galileo fifty years earlier in 1610. As the first person to use telescopes for astronomy, Galileo had charted the two big 'companions' of Saturn, that appeared and disappeared, sprouting like 'arms' from the planet. With higher quality optics, Huygens discovered that these companions were actually very thin rings, which disappeared from our sight when they were lined up with the Earth. Centuries later, the advanced optics and other instruments of Cassini and Huygens are bringing us ever closer to understand the origins of these spectacular and beautiful rings.

For fun Astronomy Outreach programs check out our Public Outreach link, or if you're interested in how you can help build the new Minnesota Planetarium, please call 612-630-6151 or visit http://www.mplanetarium.org.

Como Planetarium is offering fun family shows about astronomy on a limited basis; please call 651-293-5398 for more info!

This has been a Minnesota Starwatch produced by the University of Minnesota Astronomy Department.