dipper@utastro.UUCP (Debbie Byrd) (08/26/85)
Around this time of year you may see "the false dawn." We'll tell you what that is -- after this. August 26 The Zodiacal Light If you're planning a camping trip, be aware of a celestial phenomenon visible before dawn around this time of year. Especially if you camp in the mountains, where the nights can be cold, you might find yourself wrapped in a sleeping bag, waiting for sunrise. You may look toward the east -- and see a cone of hazy light extending up from the horizon. It looks like the sun on its way -- but don't be fooled. It isn't the sunrise, although it's been called "the false dawn. There's still another hour to go before the real dawn -- and what you're seeing is the zodiacal light. August and September are the best months to see the zodiacal light in the east before dawn. Around the first of March, the zodiacal light is easiest to see in the west after sunset. It looks kind of like an extra milky Milky Way -- very hazy and diffuse -- and maybe a little bluish. The zodiacal light extends like a cone, about 30 degrees up from the horizon. Around this time of year, it appears an hour or so before dawn begins to light the sky. Unlike the real dawn and twilight, the zodiacal light isn't caused by the atmosphere. It's caused by sunlight reflecting off dust grains that move like tiny planets in the plane of the solar system. The grains surround the sun in a thin disk -- and we see the sunlight reflected from them as an elusive cone above our horizon. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin