November 25, 2008
This story ends with the best sky show of the year--a spectacular three-way conjunction of Venus, Jupiter and the crescent Moon.
It begins tonight with a sunset stroll.
At the end of the day, when the horizon is turning red and the zenith is cobalt-blue, step outside and look southwest. You'll see Venus and Jupiter beaming side-by-side through the twilight. Glittering Venus is absolutely brilliant and Jupiter is nearly as bright as Venus. Together, they're dynamite.
Add another stick of TNT and voila!"”it's tomorrow. Go outside at the same time and look again. You'll be amazed at how much the Venus-Jupiter gap has closed. The two planets are converging, not in the slow motion typical of heavenly phenomena, but in a headlong rush"”almost a full degree (two full Moon widths) per night. As the gap shrinks, the beauty increases.
On Nov. 29th the two planets will be less than 3 degrees apart and you'll think to yourself "surely it can't get any better than this."
And then it will. On Nov. 30th a slender 10% crescent Moon leaps up from the horizon to join the show. The delicate crescent hovering just below Venus-Jupiter will have cameras clicking around the world.
Dec. 1st is the best night of all. The now-15% crescent Moon moves in closer to form an isosceles triangle with Venus and Jupiter as opposing vertices. The three brightest objects in the night sky will be gathered so tightly together, you can hide them all behind your thumb held at arm's length.
The celestial triangle will be visible from all parts of the world, even from light-polluted cities. People in New York and Hong Kong will see it just as clearly as astronomers watching from remote mountaintops. Only cloudy weather or a midnight sun (sorry Antarctica!) can spoil the show.
Although you can see the triangle with naked eyes--indeed, you can't miss it"”a small telescope will make the evening even more enjoyable. In one quick triangular sweep, you can see the moons and cloud-belts of Jupiter, the gibbous phase of Venus (69% full), and craters and mountains on the Moon. It's a Grand Tour you won't soon forget.
Finally, look up from the eyepiece and run your eyes across the Moon. Do you see a ghostly image of the full Moon inside the bright horns of the crescent? That's called "Earthshine" or sometimes "the da Vinci glow" because Leonardo da Vinci was the first person to explain it: Sunlight hits Earth and ricochets to the Moon, casting a sheen of light across the dark lunar terrain.
By itself, a crescent Moon with Earthshine is one of the loveliest sights in the heavens. Add Venus and Jupiter and "¦ well ... it's time to stop reading and go mark your calendar:
Dec. 1st @ sunset: Sky show of the year!
Image 1: Venus and Jupiter converging over Hawaii on Nov. 19, 2008. Photo credit and copyright: Stephen O'Meara.
Image 2: A sky map of the triple conjunction on Dec. 1, 2008.
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