One of my least favorite household chores is dusting. I don't know why, but if I let it go more than a week, I can write my name on the TV screen. After two weeks, geologists can do sediment dating in the stuff.
If this sounds familiar, you've probably also noticed that when the light is just right, the dust is totally invisible. But when the lighting changes – usually moments before company arrives for dinner – the room appears aglow with dust.
Well, the same thing is true in our part of the solar system. Whoever is in charge is apparently no neater than I am, because the entire inner solar system is littered with a glowing, dusty disk. And, while this interplanetary cloud is composed of different stuff than that blanketing the stereo, the principles for seeing it are similar.
Since this dusty disk lies mostly in the plane of our solar system – along the band of constellations we know as the zodiac – that's where we can see it . . . if the lighting is just right.
And so it is around this time of year, when a faint pyramid of softly glowing interplanetary dust ascends almost vertically from the eastern horizon at dawn – the “zodiacal light.”
Much harder to spot is the gegenschein, German for “counterglow,” because it appears diametrically opposite the sun.
The gegenschein appears as a faint, diffuse oval some 10 degrees across – about the size of your fist held at arm's length. Before you rush out to see it, though, remember that it's fainter than the Milky Way and 15 times fainter than the zodiacal light. Any light from the moon, street lights, haze or even bright stars or planets can make seeing it impossible. It's only visible from under the clearest, darkest sky far from cities and their suburbs.
Over the next two weeks, the gegenschein drifts eastward through the constellation Pisces. Around midnight at the end of September, you can face south and look overhead. There you'll see the Square of Pegasus, and you can use its two left stars to point southward toward the gegenschein.
Be careful not to convince yourself you see it when it really isn't there. Imagination can be a powerful force to overcome.
© Creators Syndicate Inc.
