Conjunction Junction

By Bob Berman|Friday, August 01, 1997
RELATED TAGS: MARS, METEORS & ASTEROIDS
For millions, including even not-so-devoted sky watchers, the summer’s celestial highlight is the Perseid meteor shower. This year the shower should be especially dramatic under favorable, moon-free conditions during the post-midnight, early hours of August 12. The display of shooting stars, one every minute, should successfully compete with the urge to sleep.

But something considerably rarer will also adorn the August firmament: a series of beautiful conjunctions featuring every member of the solar system that can be seen by the naked eye. None requires the slightest knowledge of constellations or the ability to identify anything more challenging than the moon. We’re talking ancient, epic-style sky watching.

The fun starts in the first week of August, as orange-flavored Mars slides in front of the vivid blue star Spica. Spica is Virgo’s brightest member, a violent sun whose lavish mass and high interior pressure crank up its nuclear furnace to a blue-hot sizzle. Spica is so luminous that it appears bright despite its daunting distance of 260 light- years.

Although Mars is merely reflecting sunlight from its dark, iron- rich surface, it shines a bit brighter than Spica because it hovers some 11 million times closer to us. And yet neither Mars nor Spica, despite occupying a vacant, non-Milky Way district of the heavens, is impressive enough to demand our gaze. But put them together and it’s another story. Suddenly, when facing south at nightfall, there’s a striking duo with vivid contrasting hues that match the official orange-and-blue colors of both New York State and the Mongolian People’s Republic.

Every night the Red Planet inches its way nearer to Spica, passing just above on August 3 and sliding away thereafter. Mars’ nightly change comes entirely from its 15-mile-per-second orbital motion. We’re too far from Mars now--138 million miles--for our own movement through space to factor into the equation. It’s one thing to have learned about the revolutions of the planets in elementary school, but this is an in-your- face display of the solar system’s movements.

Two nights after that encounter, on August 5, when twilight is still bright, peer just to the left of where the sun has set. Another rendezvous, this time a three-way meeting of the thin crescent moon, Venus, and Mercury. Venus, just now emerging from behind the sun’s glare after being lost since last winter, gleams alluringly: it’s hard to miss that single brilliant star above the moon. Mercury’s far more subtle since it’s much less bright and dangles beneath the moon in horizon murk.

Having notched our belts with the four nearest celestial bodies to Earth, it’s time for larger, more distant prey. Again, the moon obliges. We really don’t need guidance to locate Jupiter: it’s now closer to Earth than at any time in the last nine years, far and away the brightest star after nightfall. But since this is a month for observing with ease, you can abolish any challenge by waiting for August 17, when the full moon hovers next to that fascinating dollop of hydrogen. Check out its planet-class satellites (through any small telescope or steadily braced binoculars) with the knowledge that the Galileo spacecraft is now zooming by each in turn, sending us the clearest images ever of those fascinating moons.

Finally, watch the moon rise at 10:30 p.m. on August 21 and note the star floating strangely close by. That’s Saturn, its rings in view again and begging for a telescopic peek after standing edgewise for the last few years. If you find yourself spellbound by that most beautiful of all worlds, chalk it up to a bad case of conjunctionitis.
Comment on this article
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT
ADVERTISEMENT
Collapse bottom bar
DSCOctCover
+

Log in to your account

X
Email address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it emailed to you.

Not registered yet?

Register now for FREE. It takes only a few seconds to complete. Register now »