Week of Nov. 17-23, 2013

Early risers this week will see a beautiful string of planetary pearls shining at dawn, 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 lots of other stuff like dust and chunks of ice and rock. Nearly everything orbits the sun in this 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.

Normally, the location of the ecliptic isn't obvious to anyone but the astronomically savvy, but this week sky watchers can find it easily as it spans the sky from west to east.

During dawn this week you'll easily see four planets among the stars. High in the southwestern sky shines brilliant Jupiter, and farther to the east — about midway up in the southeastern sky — lies reddish Mars. Connect these two with an imaginary line and you've got the approximate path of the ecliptic. Much farther toward the east — but still along the ecliptic — lie the planets Mercury and Saturn.

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. Before sunrise on Nov. 21, the waning gibbous moon will appear just west of Jupiter, and by the next morning will have drifted along its orbit and will appear to the east of the bright planet.

Keep watch over the week and you'll see that the moon continues along this path. On the mornings of Nov. 26 and 27, the waning crescent moon will glide past Mars and, by the end of the month, will begin closing in on Mercury and Saturn which, by the way, will have reversed positions in the sky.

Over time, you will notice that the moon appears to stray somewhat from the relatively strict arc defined by the planets; that's because its orbit is tipped by about five degrees to the ecliptic, and it sometimes appears slightly above or slightly below it. And that's why we don't experience eclipses every time there is a new or full moon.

Stargazers who are uninformed about the workings of our solar system and its orientation 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 traveled this way for billions of years. If ever they don't align this way, then I'll be worried!

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.