The Sciences

Celestial Rendezvous

By Bob BermanNov 1, 1995 6:00 AM


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Planets in the night sky follow one another across the heavens like a caravan. Why? It’s because the solar system is as flat as a pancake. All the planets and most asteroids commute within the same narrow band. This celestial highway is the zodiac. As you face November sunsets, it angles steeply to the left. Following the same route, faster-moving travelers periodically pass the slowpokes. The result: Close encounters of the dazzling kind. Such conjunctions have caught people’s fancy for many millennia; we know this because ancient Chinese records chronicled the events, giving us explicit dates of planetary meetings. These meetings can be revelatory to Earthly observers. They have helped astronomers refine calculations of gravitational influences among planets. And when a planet passes directly in front of a distant star, the star’s fading light provides details about the composition of the eclipsing body. Pluto’s size and atmosphere, for instance, were discovered by this method.

A bright conjunction, however, goes further, achieving a kind of graceful celestial poetry as well as providing a dramatic, in-your-face display of planetary motion. For it’s one thing to read that Venus travels more than a million miles a day, but it’s quite another to see the evening star nearly touch Mars one night and then pull away by a moon’s width the next.

Singular brilliance and lively motion make Venus the prime conjunction maker. But Venus lines up with the outer planets--those beyond Earth’s orbit--only when those planets circle to the far side of the sun. Then you can almost feel their awesome distance as they float next to (but actually way beyond) the evening star, like faraway ships behind a nearby lighthouse. That’s what’s in store for us this month.

Venus begins a series of dramatic meetings on November 15. For the next eight days that nearest planet forms a tiny mutating triangle with Mars and Jupiter. This triple conjunction is so tight that all three worlds bunch together in the same binocular field. And binoculars are definitely a good idea: this planetary conference convenes in bright twilight.

Add half an hour to the time of your local sunset. Then sweep binoculars to the left of the sunset. Any stars seen near the horizon mean you’ve met with success. Venus is brightest, Jupiter second brightest, and Mars a very distant and orange third.

Venus and Jupiter should stand out easily to the naked eye, but an unobstructed horizon is crucial. Find a rooftop or a clearing unless you live in the Midwest, desert Southwest, or other place where open skylines are routine.

Watch Venus skim past Jupiter on No-vember 18 and 19 and graze Mars by an eyelash on the 22 and 23. Then they’ll fit in the same telescope field. That last night the moon joins the act by floating just below the trio of planets. These are the year’s best conjunctions, the kind the ancients charted with such care.

If this lively planetary choreography is hidden by clouds or buildings, mark February 1 and 2 on your calendar.

Those nights Venus, even more brilliant and much higher than it is now, will glide past an oddly ringless Saturn. The duo will be knockout obvious to the naked eye against a dark western sky at 6 P.M. Then you might want to bring your paintbrushes to the nearest cave wall. Let not the archeologists of the thirtieth century think that the inhabitants of our time ignored these marvelous meetings in the heavens.

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