Sunday, September 12, 2010

"False Dawn" Zodiacal Light


The zodiacal light, as seen from Kilimanjaro.


For the next week or so sky-watchers in the Northern Hemisphere will have the chance to see an elusive celestial pyramid known as the zodiacal light.

The triangular tower of light is easiest to spot around the spring and fall equinoxes. Look for it over the eastern horizon about an hour before sunrise in the fall, and over the western horizon just after sunset in the spring.

At best, the zodiacal light is no brighter than the dim plane of our home galaxy, the Milky Way, so atmospheric haze, a bright moon, or light pollution can hide the faint cone from view. (See a picture of the Milky Way arcing over Iran.)

In general, the zodiacal light is easiest to see in dark, rural areas, particularly on moonless nights.

September 8 saw a new moon—when the unilluminated side of the moon faces Earth—so viewing conditions should be favorable for the next few days as the waxing moon slowly returns to full brightness.

Since the light appears close to dawn in the fall, the phenomenon was often mistaken in antiquity for the light of the rising sun, and it became known as the false dawn. ...

via "False Dawn" This Week: Zodiacal Light Easier to See.

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