Moon and Venus

StarDate: July 14, 2010

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It's hurricane season -- the time of year when big storms develop over the tropics and threaten coastlines from Honduras to Nova Scotia.

The processes that help build these big storms may also help build big storms in the atmosphere of Venus, our closest planetary neighbor.

Venus has a hot, thick atmosphere that's topped by clouds of sulfuric acid. At this time last year, a bright white spot suddenly erupted in the clouds in the southern hemisphere.

Planetary scientists proposed several explanations for the spot, including a volcanic eruption on Venus's surface. But the most likely explanation seems to be weather -- an event that's similar to the processes at work in a hurricane.

The process is known as convection, where gases from deep in the atmosphere suddenly rise into the upper atmosphere. Here on Earth, that builds big thunderstorms, including those in the spiral arms of a hurricane.

On Venus, the gases are rich in sulfur and water vapor. At high altitudes, they link up to form dense clouds of sulfuric acid. These fresh clouds are quite bright, but they quickly fade as they mix with the clouds around them.

All of Venus's clouds are pretty bright, though, so they make the planet shine brightly. Look for it this evening to the upper right of the crescent Moon. It's the brilliant "evening star." The true star Regulus is to the lower right of Venus, completing a beautiful triangle in the western evening sky.

Script by Damond Benningfield, Copyright 2010

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

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