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Zodiacal light
 
 
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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
Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
 along the ecliptic
Ecliptic

The ecliptic is the apparent path that the Sun traces out in the sky during the year. As it appears to move in the sky in relation to the stars, the apparent path aligns with the planets throughout the course of the year....
 or zodiac
Zodiac

Zodiac denotes an annual cycle of twelve stations along the ecliptic, the apparent path of the Sun across the heavens through the constellations that divide the ecliptic into twelve equal zones of celestial longitude....
. In mid-northern latitudes, the zodiacal light is best observed in the western sky in the spring after the evening twilight
Twilight

Twilight is the time between dawn and sunrise, and the time between sunset and dusk. Sunlight Scattering in the upper Earth's atmosphere illuminates the lower atmosphere, and the surface of the Earth is not completely lit or completely dark....
 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
Moonlight

Moonlight is the light that comes to Earth from the Moon. This light does not originate from the Moon, but is actually reflected sunlight. However, the Moon does not Reflection sunlight like a mirror but emits light from those portions of its surface which the Sun's light strikes....
 or light pollution
Light pollution

Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light. The International Dark-Sky Association , "The Light Pollution Authority," defines light pollution as: It obscures the stars in the night sky for city dwellers, interferes with astronomy observatory, and, like an...
.






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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
Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
 along the ecliptic
Ecliptic

The ecliptic is the apparent path that the Sun traces out in the sky during the year. As it appears to move in the sky in relation to the stars, the apparent path aligns with the planets throughout the course of the year....
 or zodiac
Zodiac

Zodiac denotes an annual cycle of twelve stations along the ecliptic, the apparent path of the Sun across the heavens through the constellations that divide the ecliptic into twelve equal zones of celestial longitude....
. In mid-northern latitudes, the zodiacal light is best observed in the western sky in the spring after the evening twilight
Twilight

Twilight is the time between dawn and sunrise, and the time between sunset and dusk. Sunlight Scattering in the upper Earth's atmosphere illuminates the lower atmosphere, and the surface of the Earth is not completely lit or completely dark....
 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
Moonlight

Moonlight is the light that comes to Earth from the Moon. This light does not originate from the Moon, but is actually reflected sunlight. However, the Moon does not Reflection sunlight like a mirror but emits light from those portions of its surface which the Sun's light strikes....
 or light pollution
Light pollution

Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light. The International Dark-Sky Association , "The Light Pollution Authority," defines light pollution as: It obscures the stars in the night sky for city dwellers, interferes with astronomy observatory, and, like an...
. 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
Ecliptic

The ecliptic is the apparent path that the Sun traces out in the sky during the year. As it appears to move in the sky in relation to the stars, the apparent path aligns with the planets throughout the course of the year....
. 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
Gegenschein

Gegenschein , is a faint brightening of the night sky in the region of the antisolar point....
.

This phenomenon was first investigated by the astronomer Giovanni Domenico Cassini
Giovanni Domenico Cassini

This article is about the Italian-born astronomer. For his French-born great-grandson, see Dominique, comte de Cassini.Giovanni Domenico Cassini was an Italy/France mathematician, astronomer, engineer, and astrologer....
 in 1683 and first explained by Nicolas Fatio de Duillier
Nicolas Fatio de Duillier

Nicolas Fatio de Duillier was a Switzerland mathematician known for his work on the zodiacal light problem, for his role in the Newton v. Leibniz calculus controversy, and for originating the "push" or "shadow" theory of gravitation....
 in 1684.

Formation

The zodiacal light is produced by sunlight reflecting off dust particles in the solar system
Solar System

The Solar System consists of the Sun and those Astronomical object bound to it by gravity: the eight planets and five dwarf planets, their 173 known Natural satellite, and billions of Small Solar System body....
 known as cosmic dust
Cosmic dust

Cosmic dust is a type of dust composed of particles in space which are a few molecules to 0.1 mm in size. Cosmic dust can be further distinguished by its astronomical location; for example: intergalactic dust, interstellar dust , interplanetary dust and circumplanetary dust ....
. Consequently, its spectrum
Spectroscopy

Spectroscopy was originally the study of the interaction between radiation and matter as a function of wavelength . In fact, historically, spectroscopy referred to the use of visible light dispersed according to its wavelength, e.g....
 is the same as the solar
Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
 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
ORBit

ORBit is a Common Object Request Broker Architecture 2.4 compliant Object Request Broker . It features mature C , C++ and Python bindings, and less developed bindings for Perl, Lisp , Pascal , Ruby , and Tcl....
 of Earth. This material is known as the interplanetary dust cloud
Interplanetary dust cloud

The interplanetary dust cloud is cosmic dust which pervade the space between planets in the Solar System and in other planetary systems. It has been studied for many years in order to understand its nature, origin, and relationship to larger bodies....
. 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
Albedo

The albedo of an object is the extent to which it diffusely reflects light from the Sun. It is therefore a more specific form of the term reflectivity....
 (reflecting power) as Earth's moon
Moon

The Moon is Earth's only natural satellite and the List of natural satellites by diameter satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is km, about thirty times the diameter of the Earth....
, each particle would be 8 km from its neighbors. The gegenschein may be because particles directly opposite the sun as seen from Earth would be in full phase
Lunar phase

Lunar phase refers to the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases vary cyclically as the Moon orbits the Earth, according to the changing relative positions of the Earth, Moon, and Sun....
.

The Poynting-Robertson effect
Poynting-Robertson effect

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 a dust grain in the solar system to slowly spiral inward....
 causes the particles to spiral slowly into the Sun, thus requiring a continuous source of new particles to maintain the zodiacal cloud. Comet
Comet

A comet is a Small Solar System body that orbits the Sun and, when close enough to the Sun, exhibits a visible coma or a tail?both primarily from the effects of solar radiation upon the Comet nucleus....
ary dust and dust generated by collisions among the asteroid
Asteroid

Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, smaller than planets but larger than meteoroids....
s are believed to be mostly responsible for the maintenance of the dust cloud producing the zodiacal light and the gegenschein
Gegenschein

Gegenschein , is a faint brightening of the night sky in the region of the antisolar point....
. 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
Minor planet

An asteroid group or minor planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid....
 and several cometary trails.

Historical explanations


Previously, it was believed that zodiacal light was just the atmosphere of the sun
Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
. According to the 1728 Cyclopaedia:

"The zodiacal light is nothing but the solar atmosphere, a rare and subtile fluid, either luminous by itself, or made so by the rays of the sun surrounding its globe; but in a greater quantity, and more extensively, about its equator, than any other."


Importance to Islam


The Prophet Muhammed is known to have described zodiacal light in reference to the timing of the five daily prayers, calling it the "false dawn," or "al Fajr al Khaadib." Muslim oral tradition preserves numerous sayings, or hadith
Hadith

Hadith are oral traditions relating to the words and deeds of the Prophets of Islam Muhammad. Hadith collections are regarded by all traditional madhab as important tools for determining the Muslim way of life, the sunnah....
, in which Muhammed describes the difference between the light of false dawn, appearing in the sky long after sunset, and the light of the first band of horizontal light at sunrise, the true dawn. Practitioners of Islam
Islam

Islam is a Monotheism, Abrahamic religion originating with the teachings of the Prophets of Islam Muhammad, a 7th century Arab religious and political figure....
 use the Prophet's descriptions of zodiacal light to avoid errors in determining the timing of daily prayers.

Such practical descriptions and applications of astronomical observations were vital to the golden age of Islamic astronomy
Islamic astronomy

In the history of astronomy, Islamic astronomy or Arabic astronomy refers to the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language....
.

Trivia

Recently, after a 30-year break from his studies to play guitar with multi-platinum rock group Queen
Queen (band)

Queen were an England rock music band formed in 1970 in London by guitarist Brian May, lead vocalist Freddie Mercury and drummer Roger Meddows-Taylor, with bassist John Deacon completing the lineup the following year....
, guitarist Brian May published his doctoral thesis on zodiacal light, entitled, "A Survey of Radial Velocities in the Zodiacal Dust Cloud." He subsequently received his Ph.D in Applied Astrophysics from Imperial College London.

See also

  • Optical phenomenon
    Optical phenomenon

    An optical phenomenon is any observable event which results from the interaction of light and matter. See also list of optical topics and optics....
  • Zodiacal dust
    Zodiacal dust

    Zodiacal dust forms a pancake shaped cloud in the Solar System collectively known as the zodiacal cloud. It occupies the same plane as the orbit of the planets from which it derives the name zodiac....
  • Islamic astronomy
    Islamic astronomy

    In the history of astronomy, Islamic astronomy or Arabic astronomy refers to the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language....


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