zodiacal light

a luminous tract in the sky, seen in the west after sunset or in the east before sunrise and thought to be the light reflected from a cloud of meteoric matter revolving round the sun.

[1725-35]

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Band of very faint light in the night sky.

It is thought to be sunlight reflected from interplanetary dust grains lying mostly in the plane of the zodiac, or ecliptic. Seen in the west after twilight and in the east before dawn, it is most clearly visible in the tropics, where the ecliptic is approximately perpendicular to the horizon. In midnorthern latitudes it is best seen evenings in February and March and mornings in September and October (vice versa in midsouthern latitudes). The light can be followed visually to a point about 90° from the Sun. It continues to the region opposite the Sun, where a slight enhancement, the gegenschein, is visible.

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▪ astronomy

      band of light in the night sky, thought to be sunlight reflected from meteoroids concentrated in the plane of the zodiac, or ecliptic. The light is seen in the west after twilight and in the east before dawn, being easily visible in the tropics where the ecliptic is approximately vertical. In mid-northern latitudes it is best seen in the evening in February and March and in the morning in September and October.

      The zodiacal light can be followed visually along the ecliptic from a point 30° from the sun to about 90°. Photometric measurements indicate that the band continues to the region opposite the sun where a slight enhancement called the gegenschein, or counterglow, is visible. There is some zodiacal light in all parts of the sky; it can be considered an extension of the F-corona of the sun.

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