Venus and Saturn

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Venus and Saturn will just slip past each other in tomorrow's early dawn sky. Venus is the brilliant "morning star." Fainter Saturn is just to its left or upper left. At their closest, the two planets will be separated by about the width of a pencil held at arm's length. But they're quite low in the sky, so you'll need a clear eastern horizon to spot them.

The Cassini spacecraft is orbiting Saturn, and it has a busy few days lined up. Today, it's scheduled to fly about 800 miles from Saturn's largest moon, Titan. And tomorrow and Wednesday, it'll scan six of the planet's smaller moons at distances ranging from about 25,000 to 60,000 miles.

Titan is the jewel of the Saturn system because it's enveloped in a thick, cold atmosphere. The atmosphere is topped by an orange haze that's similar to smog here on Earth. Cassini has provided our first view through the smog, revealing an amazing world below.

It found that the atmosphere supports complex weather patterns, for example, and flowing liquids that carve rivers and fill hundreds of lakes. The liquid isn't water, though -- Titan is so cold that water is frozen as hard as granite. Instead, it's methane.

Titan also appears to have ice volcanoes. And giant dunes of frozen hydrocarbons undulate across thousands of square miles around the moon's equator. They help make Titan one of the most interesting moons in the solar system -- a frozen world that looks a lot like Earth.

Script by Damond Benningfield, Copyright 2009

For more skywatching tips, astronomy news, and much more, read StarDate magazine.