The zodiacal light in the eastern sky before the beginning of morning twilight. A reddish auroral glow can also be seen near the horizon, especially at the left.

The zodiacal light is a faint, roughly triangular, whitish glow seen in the night sky which appears to extend up from the vicinity of the sun along the ecliptic or zodiac. In mid-northern latitudes, the zodiacal light is best observed in the western sky in the spring after the evening twilight has completely disappeared, or in the eastern sky in the autumn just before the morning twilight appears. It is so faint that it is completely masked by either moonlight or light pollution. The zodiacal light decreases in intensity with distance from the Sun, but on very dark nights it has been observed in a band completely around the ecliptic. In fact, the zodiacal light covers the entire sky, being responsible for 60% of the total skylight on a moonless night. There is also a very faint, but still slightly increased, oval glow directly opposite the Sun which is known as the gegenschein. Image File history File links Zodiacal_light. ... Image File history File links Zodiacal_light. ... It has been suggested that this article or section be merged with Dawn. ... Aurora borealis Aurora Australis For other meanings, see Aurora. ... The Sun (or Sol) is the star at the center of our Solar system. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... Zodiac signs, 16th century , medieval woodcuts The zodiac (from Greek zoon, animal) is an imaginary belt in the heavens extending approximately 8 degrees on either side of the Suns apparent path (the ecliptic), that includes the apparent paths of the Moon and the planets Mercury, Venus, Mars, Jupiter, Saturn. ... Spring is one of the four seasons of temperate zones. ... It has been suggested that this article or section be merged with Dawn. ... Autumn (often referred to as fall in North America) is one of the four temperate seasons, the transition from summer into winter. ... Moonlight has several meanings: Moonlight is the light that is perceived as coming from the moon. ... This composite satellite photograph of the earth at night demonstrates how much of the worlds light is projected into space, rather than on its intended target. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... Gegenschein (German for counterglow) is a faint brightening of the night sky in the region of the zodiac directly opposite the Sun caused by reflection of sunlight by small dust particles that lie in the plane of the Solar system. ...

The zodiacal light is produced by sunlight reflecting off dust particles which are present in the solar system and, consequently, its spectrum is the same as the solar spectrum. The material producing the zodiacal light is located in a lens-shaped volume of space centered on the sun and extending well out beyond the orbit of Earth. This material is known as the interplanetary dust cloud. Since most of the material is located near the plane of the solar system, the zodiacal light is seen along the ecliptic. The amount of material needed to produce the observed zodiacal light is amazingly small. If it were in the form of 1 mm particles, each with the same albedo (reflecting power) as Earth's moon, each particle would be 5 miles from its neighbors. The gegenschein may be due to the fact that particles directly opposite Earth from the sun would be in full phase. This article describes dust in the astronomical cosmic context, of which interplanetary dust and interstellar dust are particular types. ... Presentation of the solar system (not to scale) The solar system comprises our Sun and the retinue of celestial objects gravitationally bound to it. ... Extremely high resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of spectra, that is, the dependence of physical quantities on frequency. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... Interplanetary dust cloud The interplanetary dust cloud has been studied for many years in order to understand its nature, origin, and relationship to solar systems (our own, as well as extrasolar systems). ... The albedo is a measure of reflectivity of a surface or body. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... In astronomy, a phase of the Moon is any of the aspects or appearances presented by the Moon as seen from Earth, determined by the portion of the Moon that is visibly illuminated by the Sun. ...

Sunlight absorbed by the dust particles is re-emitted as infrared radiation. This reradiation causes the particles to spiral slowly into the Sun (Poynting-Robertson effect), thus requiring a continuous source of new particles to maintain the zodiacal cloud. Cometary dust and dust generated by collisions among the asteroids are believed to be responsible for the maintenance of the dust cloud producing the zodiacal light and the gegenschein. In recent years, observations by a variety of spacecraft have shown significant structure in the zodiacal light including dust bands associated with debris from particular asteroid families and several cometary trails. Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... The Poynting-Robertson effect, also known as Poynting-Robertson drag, named after John Henry Poynting and Howard Percy Robertson, is a process by which solar radiation causes dust particles in a solar system to slowly spiral inward. ... Photo of the comet Hale-Bopp above a tree. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... Minor planets, or planetoids are minor bodies of the Solar system orbiting the Sun (or of other planetary systems orbiting other stars) that are larger than meteoroids (the largest of which might be taken to be around 10 meters or so across) but smaller than major planets (Mercury having a...

This phenomenon was first investigated and explained by the astronomer Gian Domenico Cassini about 1690. This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

See also

• Optical phenomenon

An optical phenomenon is any observable event which results from the interaction of light and matter. ...

External links

• A Brief History of Observations
• "Zodiacal Light and the Gegenschein", an essay by J. E. Littleton

Reference

Wikimedia Commons has media related to:

Zodiacal light

• Reach, W. T. (1997). "The structured zodiacal light: IRAS, COBE, and ISO observations". Diffuse Infrared Radiation and the IRTS. ASP Conference Series. 124, 33-40

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