Light zodiacale

The light zodiacale is a weak triangular gleam which can be perceived on the night sky and which extends starting from the surroundings from the Sun along the plan from the ecliptic (or of the Zodiaque which gave him its name).

Principle

The light zodiacale is produced by the reflection of the Lumière of the Sun by the particles of dust of the interplanetary Milieu present in the Solar system. The materials which cause it are distributed in a volume in the shape of lens centered on the Sun and extending well beyond the Orbite from the Ground. As the majority of these particles are located close to the plan of the ecliptic, the light zodiacale mainly seems to come from it.

Characteristics

The quantity of particles of dust necessary to produce the light zodiacale is extremely weak: if the particles had a diameter of 1 mm and same the Albédo that the the Moon, it would be enough that each particle is distant of its neighbors of almost 10 km.

The spectrum of the light zodiacale is the same one as that of the Sun. Nevertheless, part of the sunlight is absorbed by the particles of dust and is re-emitted in the form of radiation Infrarouge. This emission induces a slow spiral of the particles towards the Sun, known under the name of Effet Poynting-Robertson, which implies that a continuous source of particles is necessary in order to maintain the light zodiacale. It is thought that the Comet S and the Astéroïde S are responsible for this phenomenon. These last years, of the observations carried out by several interplanetary probes showed that bands of dust associated with various families with asteroids and with cometary tails seem related to the structure of the light zodiacale.

Observation

The light zodiacale is very slightly luminous and is completely masked by the light of the Moon or the luminous Pollution. With the average latitudes north, one best observes it towards the west in spring, after the twilight, or towards the east with the autumn, right before the paddle.

The light zodiacale decrease in luminosity with the distance to the Sun, but by certain very black nights, one can observe a continuous band from approximately 5 with 10° of broad all along the ecliptic, known under the name of band zodiacale. In fact, the light zodiacale covers the sky in its entirety and is the source of 60% of the one night luminosity without the Moon. Contrary to the light zodiacale, it is possible to observe a known very weak oval gleam under the name of Gegenschein .

As of the 19th century of the researchers, whose Svante August Arrhenius whose imagined that this light could give information on the nature of the particles present in space where it is visible.

See too

Internal bonds

interplanetary Gegenschein
Medium
optical Phenomenon

External bonds

References

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