dipper@utastro.UUCP (Debbie Byrd) (08/29/84)
This is a good time of year to see the zodiacal light. More on the so-called "false dawn" -- right after this. August 28 The Zodiacal Light A mysterious pyramid of light can be seen before dawn in late August and early September. The zodiacal light -- sometimes called the "false dawn" -- is visible from country locations above the eastern horizon an hour or so before real dawn washes the sky. The zodiacal light is even milkier-looking than the summer Milky Way. It's so large and obvious that it's easy to miss, since you may be expecting something smaller. This soft light resembles the glow of a town or city on the horizon. But it originates in outer space, where sunlight reflects off dust in the plane of the solar system. This zodiacal band of dust has been known for some time. But recently it was learned that this one band is flanked by additional dust bands -- possibly the result of collisions between asteroids, or a single catatrophic collision between an asteroid and a comet. IRAS, the Infrared Astronomical Satellite, revealed the complex nature of dust in our solar system while orbiting Earth last year. So the zodiacal light -- or false dawn -- originates in outer space. It's often seen and maybe almost as often ignored by country dwellers, wakeful campers and people who get up before dawn to start a long drive to the east. If you're out before dawn in the country, look toward the east for a large, hazy cone of light. The way to tell the false dawn from the real dawn is to check the time -- if it's an hour or so before real twilight begins, then you're seeing the zodiacal light. Script by Deborah Byrd. (c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin