Planets Dance in the Predawn Light

Planets Dance in the Predawn Light
by Dave Adalian

Early risers and those who like to stay up until dawn will be treated to a planetary dance if they’ll look to the east before first light all next week.

On Sunday morning just before the Sun rises three planets will hover just above the eastern horizon. Brightest and easiest to find of the trio will be Earth’s twin sister Venus.

This 8,000-mile-wide orb is about the same size as our own planet, but covered with a planet-wide haze that reflects back much of the light that strikes it, making it one of the most dazzling sights in the night sky.

Closer to the horizon and to the left of Venus will be a close pairing of Mercury and Saturn. On Sunday morning, Mercury will sit about a degree above the ringed planet and both will be very close to the horizon. Twenty-four hours later, the pair will have switched positions, with swift-footed 3,000-mile-wide Mercury moving so quickly toward the Sun it will appear about one degree below slower-moving Saturn.

Also joining the dance on Monday morning will be a very slender crescent moon sitting above the planetary trio. The Moon will be even thinner still, as thin as you are ever likely to see it on the last day of its 28-day cycle, on Tuesday morning when it floats near Saturn’s left-hand side.
For a striking example of what a difference distance makes for planetary viewing, remember that our moon is just 850 miles more narrow than faraway Mercury but appears roughly 166 times larger to the naked eye.

By Wednesday morning, Venus and 75,000-mile-wide Saturn will be all alone in the eastern sky with Mercury lost in the wash of predawn brightening.

Their other dance partners now gone, Venus and Saturn will go it alone over the next several mornings while Venus makes its way closer to Saturn and sunup each day.

On Tuesday, with the Moon close at hand, Saturn and Venus were some 5 degrees apart, by Friday the gap will have narrowed to less than 2 degrees, or about four times the width of the full moon.

The gap will be at its smallest over the weekend when Venus will be less than one degree above Saturn, and the final move of the celestial cotillion will come on Sunday morning when the two change position, with Saturn now less than a degree above Venus.

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Join the Tulare Astronomical Association for its monthly public star party this Friday, 9-11 p.m., at the Arthur L. Purcell Observatory, 9242 Ave. 184, south of Tulare and 2.1 miles west of Highway 99. Information and direction: http://starry-starry-nights.blogspot.com/.

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This column originally appeared in the Visalia (Calif.) Times-Delta and Tulare (Calif.) Advance-Register on Aug. 17, 2006.