Stargazers: See a planetary string of pearls


A beautiful string of planetary pearls shines at dawn right now, but one of the coolest sights of the early morning sky is one that's completely invisible.

Well, sort of.

Stargazers who know something about astronomy can find it on most nights and mornings but, unfortunately, most will not realize its true significance. I'm referring, of course, to the geometric plane of our solar system.

We know that our solar system includes the planets, the sun, moon, comets, asteroids and tons of other stuff, like dust and chunks of ice and rock. Nearly everything orbits the sun in a geometric plane, the result of our planetary system's birth from a rapidly spinning disk billions of years ago.

From within, we see this plane as an arc across our sky; it represents the general paths that the sun, moon and planets take on their journeys through the starry heavens. We call it the "ecliptic" because it is along this arc that the sun and moon appear to travel and, therefore, the only place where eclipses can occur.

The ancients recognized this arc also, but, of course, did not understand its significance. So they devised 12 stellar groupings to mark its position, and knew it as the zodiac among which their gods appeared to wander. This week, the zodiac constellations that appear at dawn are — from west to east: Leo, Virgo, Libra, Scorpius and Sagittarius.

And this week sky watchers can find along the ecliptic all five visible planets ... and the moon!

At dawn or shortly before, gaze toward the southwestern sky and you'll see the bright planet Jupiter, the second brightest planet. Farther toward the east (and almost due south at dawn) you'll spot the Red Planet Mars. Though it doesn't appear terribly bright right now, it will later in the spring when it comes closer to the Earth.

Trace a line between these two planets and you've got the beginning of the ecliptic. Farther to the east you'll encounter Saturn, just short distance from — and slightly brighter than — the reddish star Antares.

Next on the arc of the ecliptic, you'll find brilliant Venus low in the southeast. And below it, very close to the southeastern horizon, you should spot Mercury.

Since this arc also represents the general path that the moon takes as it orbits the Earth each month, watch during the week as the waning moon glides along it from morning to morning. At dawn on Jan. 27, the moon will appear just below and to the west of Jupiter; on Jan. 28 it will appear to its east.

By Feb. 1, you will see the last quarter moon next to Mars, and on Feb. 3 above Saturn. And on Feb. 6, the thin crescent moon will form a nice triangle with Venus and Mercury.

Stargazers who are uninformed about the workings of our solar system and its appearance in the sky will undoubtedly interpret this configuration as an "alignment" of the planets — something with important supernatural significance.

I'm not too worried, though... the planets have behaved this way for billions of years. If ever they don't align this way, then I'll be worried!

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