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    The Zodiacal Light

    By travel
    9/30/2013, 4:23:33 AM

    This blog is written by Paul Adomshick of AccuWeather Astronomy on Facebook.

    Around the fall and spring equinoxes, an astronomical phenomena known as the zodiacal light becomes more visible for a few weeks.

    The zodiacal light is the result of sunlight reflecting off solar system dust. The conditions for this light being bright enough to be seen are best before the morning twilight hours in the fall, and after the evening twilight hours in the spring. As we are in the prime time for fall viewing of the zodiacal light, being close to the equinox, but not near full moon, the description of the phenomena will be in terms of the eastern sky, dawn and morning twilight. If you are looking for the spring zodiacal light, just think in terms of the western sky, dusk and evening twilight.

    Zodiacal Light over the Faulkes Telescope, Haleakala, Maui. Photo credit: Wikimedia Commons


    In order to see the zodiacal light, you will need dark sky conditions. Light pollution and the glow of the moon overwhelm its very faint light. If you have any light pollution to your east, it is almost certain that you will not be able to see it. It is generally fainter than the Milky Way, but in dark sky conditions, it can be quite prominent. It can resemble the light pollution of an isolated town on the horizon in a rural area, and is sometimes mistaken for light pollution. Because we are nearing the new moon this week, the glow of the moon will not wash out the zodiacal light.

    The zodiacal light appears as a wedge of light, wide at the horizon, and narrowing the farther it gets from the horizon. The wedge is tilted, and points along the ecliptic, which is the flat plane that the orbits of the planets lie in. It is usually easier to see the closer you are to the tropics, because the path of the ecliptic tends to be more directly overhead.

    The zodiacal light is often called a “false dawn” because it is seen in the same part of the sky as the first light of dawn. However, the two phenomena are different, because the zodiacal light is sunlight reflected off solar system dust, whereas the light of dawn is sunlight lighting up our own planet's atmosphere. Once true dawn conditions begin, the zodiacal light is too dim to be seen. If you happen to be outside over the next week or two, in the hours before dawn, in a dark sky area, take a look to the east, and you may get your chance to see the zodiacal light.

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    Astronomy blog