Week of May 26 — June 1, 2013

I hope you've been paying attention to the marvelous dance of the planets taking place low in the western sky at dusk. What a great opportunity to see how the worlds of our solar system move in their orbits, and all within only a few days.

Head outdoors shortly after sunset and you will easily spot a trio of planets — Mercury, Venus and Jupiter — that are changing their apparent positions from night to night. The brightest of the three is Venus, the Earth-sized world that is shrouded in sunlight-reflecting clouds. The faintest is Mercury, the tiny rocky world that lies closest to the sun.

If you haven't been following the sky show, now's a great time to begin. In fact, at dusk on Sunday, May 26, the three worlds will appear in their most compact arrangement. In fact, if you have binoculars, you'll be able to see all three in the same field of view. And if you wait until they drop a bit lower and the horizon enters the field of view, you'll see a fourth planet as well (the Earth)! That's half of the solar system's planets in one field of view!

That we can see all these worlds one small region of space, of course, is purely an illusion. These planets are really millions of miles apart from one another but because of their movements now appear roughly along the same line of sight from our vantage point. On May 26, for example, Jupiter lies on the opposite side of the sun — 564 million miles from Earth — nearly as far as it ever becomes. Venus, on the other hand, lies 153 million miles, and Mercury only 106 million miles from Earth.

Within only a few days, the three planets will appear to separate. While the show began last week with Venus closest to the horizon and Jupiter highest in the sky, the whole configuration will reverse itself this week. By May 29, stargazers will easily notice that Jupiter is descending from night to night, while Venus and Mercury appear to be ascending. By the first day of June, the trio will be widely separated with Mercury highest in the sky and Jupiter closest to the horizon.

One thing you might notice is that these planets appear to twinkle. Now this seemingly contradicts what most of us learned in school — that stars twinkle but planets don't. This is one of those many facts we learned that just is not true.

The twinkling we see is the result of unstable air moving in front of distant lights and causing them to appear to shimmer. We see this frequently when we look over a hot campfire; distant objects appear to be bouncing around. When a star's light passes through our turbulent atmosphere, its thin light beam is also distorted and bent — thousands of times per second — and we see the stars as appearing to twinkle. And the same is true for planets, mostly when they appear near the horizon.

Whether you're out barbequing or just enjoying the early evening this week, be sure to cast your gaze skyward for a show you won't soon forget!

Visit Dennis Mammana at www.dennismammana.com. To read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.