The zodiacal light is a faint band of white light diffuse cone-shaped, seen in the night sky and stretching along the ecliptic plane. It is produced by reflection of sunlight on dust particles in the interplanetary medium. It still appears in the constellations of the zodiac, whence its name.
The reason for the zodiacal light is not visible all year is its low density. To see the ecliptic must lie vertically over the horizon, which comes only from February to March and September to October.
The gravitational influence of Earth on the zodiacal dust cloud has been highlighted by the IRAS satellite in 1994 and COBE in 1995.
The Earth has the effect of retaining dust particles tend to fall into the Sun under the Poynting-Robertson. It then formed along the orbit of the Earth, a ring of dust that will be reflected in the atmosphere under certain conditions.
On the right of this picture taken in July 2009 in Laguna Verde, near Valparaiso, Chile, one sees this band of white light and diffuse. On the left we see the bright band of the Milky Way, which opposes the zodiacal light.
The dust responsible for the zodiacal light revolve around the sun in substantially the same plane as the planets, i.e. the ecliptic plane. When the ecliptic is nearly vertical to the horizon, as in this picture, just before sunrise, the zodiacal light is distributed vertically in the atmosphere.
Periods of observation of the zodiacal light to the inhabitants of the northern hemisphere, are the months of March and April just after sunset or October, just before dawn. In the southern hemisphere, the zodiacal light is visible at the end of the summer after sunset and before sunrise in late spring.
There are few traces of observations that light before those of Jean-Dominique Cassini conducted between 1683 and 1693.
The zodiacal light is a phenomenon that comes from the reflection of starlight on dust around it. The study of such dust disks allows scientists to see if there are planets in formation around the star.
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Image: In this image taken in July 2009 in Laguna Verde, near Valparaiso, Chile, we see the zodiacal light on the right. The zodiacal light is seen when the sky is pure, mid-latitude north looking west in the spring, after sunset or east in the fall, just before dawn. Credit & Copyright: Manel Soria.