The light beam formed by the reflection of sunlight from the dust particles around the sun
Zodiacal light is the reflection of light from the sun by some dust particles that constantly surround the sun.The silvery white light cone formed on the ecliptic plane due to the scattering of solar light by interplanetary dust is generally triangular and roughly parallel to the ecliptic planesunlightDirection enhancement.Generally speaking, the ecliptic light is very weak, and it is not easy to see except that it is barely visible after dusk in spring or before dawn in autumn under ideal observation conditions.Zodiacal light existsInterplanetary matterProof of.The infrared zodiacal light taken by the IRAS spacecraft shows a flat, lenticular shape (see figure), which extends along the plane of the ecliptic to both sides (reference: Sykes, M. V. (2007))Infrared views of the solar system from space.Aas/division for Extreme Solar Systems Abstracts, 681-694.Encyclopedia of the Solar System）
The sun sets in the west, and after dusk, a flame like light can sometimes be vaguely seen in the western sky.Similarly, when the sun rises in the east and the dawn does not appear, you can also see a ray of light extending upward from the horizon in the east.It is difficult to observe this astronomical scene in the days when there are bright celestial bodies such as the moon, Venus and Jupiter, but it can surprise those who see it in the night when there is no moon.
No matter who looks carefully, he will find that the bright light is very wide near the horizon, and gradually narrows to the zenith, like a flame tongue.This is the zodiacal light.
features
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Ecliptic light
Ecliptic light（zodiacal light）
be locatedearthUp and downlatitudeThe faint triangular cone of light seen on the western horizon after dusk in spring or on the eastern horizon before dawn in autumn.EclipticLight extends upward along the ecliptic, reaching about 30 ° above the horizon.
Its visible time is not long.Seen after dusk in springEcliptic light, gradually disappear as the night falls completely;autumndawnThe zodiacal light I saw earlier disappeared into the dawn as the east gradually turned white.
Ecliptic lightVery weak, must be in goodEnvironmental ScienceCan be observed effectively.The spatial direction of the ecliptic plane after dusk in spring and before dawn in autumn is exactly the closest to the vertical ground plane, so the ecliptic light will rise higher and be easy to see.
Near the equator, the ecliptic plane is sometimes completely perpendicular to the local horizon, which is more conducive to observation.In addition to the advantages of low latitude, the observation point should be selected at a place with high altitude as far as possible to achieve good atmospheric transparency and avoid the interference of artificial light sources;To avoid possibleaurora, it is better to observe at low magnetic latitude;Of course, the observation point should also have good weather conditions, that is to say, it should chooseVernal equinox、the autumnal equinoxBefore and after (the most favorable time to observe the zodiacal light), there are places with continuous sunny nights and transparent and stable atmosphere.
When the observation conditions are excellent (e.gearthatmosphereYou can also see the zodiacal light extending inward to the sun and covering the whole sky outward.It forms a brighter belt along the ecliptic, calledzodiac。The two sides of the ecliptic belt are parallel to the ecliptic, extending from the top of the ecliptic light cone to the direction away from the sun, and the brightness continues to decline until it is about 135 degrees away from the sun.After that, the brightness rose again and began to reach a maximum near the anti sun point.There is a 20 ° × 10 ° light area near the anti sun point that is brighter than the surrounding area, calledSunshine。
Chinastayyuan dynastyThere have been observations of zodiacal light since the early days.Italian astronomer GD.CassiniZodiacal light was observed on March 18, 1683, and systematic research was first carried out.
cause
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Ecliptic light
Ecliptic lightThe main reason is the scattering of sunlight by interplanetary dust.Therefore, the spectrum of zodiacal light is very similar to that of the sun.It is generally believed that lineInterstellar dust particlesAfter the asteroid is crushed orcometThe product of disintegration.They are basically scattered on and near the plane of the ecliptic, so the light of the ecliptic extends roughly along the plane of the ecliptic.In addition, there may be a small part of zodiacal light distributed in interplanetary spaceElectronic cloudFormed by scattering.In the vicinity of the Earth's orbit, the density of the number of electrons in the electron cloud is about the order of 100-1000 per cubic centimeter.
People's research travelInterstellar matterThere are two main methods of GPS: one is to send the interplanetary probe to the field for sampling;Second, the observational characteristics of zodiacal light (includingstrength、polarization、spectrum, color, etc.)Interplanetary matterThe nature of (density, distribution, shape, size, etc.).The former method is direct, but the cost is huge, and the number and scope of flights are limited;Although the latter method is indirect, it is economical and convenient, and can be observed for a long time, so it is still often used today.
The interplanetary matter is roughly symmetrically distributed around the sun, in which there are a large number of dust particles as small as 1 μ m or even 0.1 μ m. Their distribution is that the farther away from the sun, the smaller the number, and the number of small particles is much more than that of large particles.These conclusions from the observation of zodiacal light are consistent withSpace probeThe measured results are in good agreement.
The above distribution of interplanetary matter inevitably leads to two symmetries of the main part of the ecliptic light: ① symmetry to the ecliptic plane; ②Symmetric to the yellow circle passing through the sun.This has been fully confirmed by a large number of observations.
brightness
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Ecliptic light
Ecliptic lightThe brightness increases monotonously towards the sun, which can be considered as externalCoronaAn extension of.That is, near the sun, the zodiacal light blends inF Corona（Dust corona）And become part of the outer crown.However, the brightness of zodiacal light is not fixed, it has short-term changes and long-term changes, and the reasons are very complex.For example, it has been pointed out that solar activity affects the brightness of zodiacal light.
Overlapping with zodiacal lightNight skylightIn addition, it is necessary to distinguish between "true zodiacal light" (that is, the zodiacal light measured on the surface of the earth's atmosphere and corrected) and "zodiacal light" (that is, the zodiacal light changed by the scattering of the earth's atmosphere).It is difficult to deduce the true zodiacal light from the zodiacal light, and most of the uncertainty of the observation results comes from this.
Poyntine Robertson effectIt will cause dust particles to slowly enter the sun in a spiral path, so there must be a steady stream of new dust particles to supplement the clouds in the ecliptic.come fromcometDust tail andasteroidThe dust particles generated by the collision are the main source of particles that supplement and form zodiacal light and sunlight.Observations from different spacecraft show that there are indeed some dust particles with banded distributionasteroid family It is related to the comet tail.
In 2010, according to the online edition of Science magazine in the US, the US planetary dynamics home computer model solved the mystery of the night sky glow - the mystery of the formation of zodiacal light.It is concluded that almost all the zodiacal light dust comes fromShort period comet, overturning the long held speculation.
observation
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When the observation conditions are very good (such as outside the earth's atmosphere), you can also see that the ecliptic light extends tosunlightNearby, outward all over the sky.A bright belt is formed along the ecliptic, called the ecliptic belt.The two sides of the ecliptic belt are parallel to the ecliptic, extending from the top of the ecliptic light cone to the direction away from the sun, and the brightness continues to decline until it is about 135 ° away from the sun.After that, the brightness rose again and reached a maximum near the anti sun point.There is a light area of about 20 ° × 10 ° near the anti sun point, which is brighter than the surrounding area, called the sunshine.
The zodiacal light is a triangular cone along the ecliptic, just like a tongue like dim light. The closer it is to the horizon, the more it expands and the brighter it becomes.In mid latitudes, it is usually easier to see the eastern horizon after sunset in spring or before sunrise in autumn.The best viewing time is before the beginning of astronomical dawn (autumn) or after the end of astronomical twilight (spring).
Ecliptic light
The sunshine is the light image at the place opposite to the sun and 180 degrees away from it,RangeThe small ellipse with a size of about 20 °× 10 ° and a dim light is caused by the back scattering of sunlight through dust particles.It can only be observed in an environment free from light damage and moonlight.
Conditions
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Zodiacal light is located in the low and middle latitudes of the earthlatitudeThe faint triangular cone of light seen on the western horizon after dusk in spring or on the eastern horizon before dawn in autumn.The zodiacal light extends upward along the ecliptic, reaching about 30 degrees above the horizon.The visible time is not long.The zodiacal light seen after the spring dusk gradually disappears as the night falls completely;The zodiacal light seen before dawn in autumn gradually fades into the dawn with the east.The zodiacal light is very weak, and only under good environmental conditions can it be observed effectively.
The spatial direction of the ecliptic plane after dusk in spring and before dawn in autumn is exactly the closest to the vertical ground plane, so the ecliptic light rises higher and is easy to see.Near the equator, the ecliptic plane is sometimes completely perpendicular to the local horizon, which is more conducive to observation.In addition to the advantages of low latitude, the observation point should be selected at a place with high altitude as far as possible to achieve good atmospheric transparency, avoid the interference of artificial light sources, and avoid possibleaurora, it is better to observe at low magnetic latitude;Of course, the observation point should also have good weather conditions, which means that it should choose a place with continuous sunny nights, transparent and stable atmosphere around the spring and autumn equinoxes (the most favorable time for observing the zodiacal light).
It is easy to see zodiacal light in the western sky after sunset from January to March, and in the eastern sky before dawn from October to November.This is because during these two periods, the angle between the ecliptic and the horizon is relatively large, and will not be disturbed by the Milky Way.Outdoor lighting will worsen astronomical observation conditions, and even the Milky Way will not be visible.In this sense, it can also be said that zodiacal light is an "endangered species" in the night sky, while for sunlight, it is already an "extinct species".
There were observations of zodiacal light in China in the early Yuan Dynasty.Italian astronomer GD. Cassini began to observe the zodiacal light on March 18, 1683, and was the first to carry out systematic research.
Causes
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Ecliptic light
The cause of zodiacal light is mainly the scattering of solar light by interplanetary dust.Therefore, the ecliptic light spectrum is very similar to the solar spectrum.It is generally believed that the interplanetary dust particles areasteroidAfter being crushed orcometThe product of disintegration.Basically, it is scattered on and near the ecliptic plane, so the ecliptic light extends along the ecliptic plane.In addition, a small part of zodiacal light may be formed by scattering of electron clouds distributed in interplanetary space.In the vicinity of the Earth's orbit, the density of the number of electrons in the electron cloud is about the order of 100-1000 per cubic centimeter.
research method
Methods for studying interplanetary matter:
There are generally two methods for people to study interplanetary matter: sending interplanetary probes to the field for sampling;Observational characteristics of zodiacal light (including intensity, polarizationspectrum, color, etc.).The former method is direct, but it costs a lot of money, and the number and scope of flights are limited;Although the latter method is indirect, it is economical and convenient, and can be observed for a long time, so it is still often used.
Roughly distributed
Approximate distribution of interplanetary matter:
The interplanetary matter is roughly symmetrically distributed around the sun, in which there are a large number of dust particles as small as 1 μ m or even 0.1 μ m. The distribution is that the farther away from the sun, the smaller the number isparticleThere are many more than large particles.These conclusions from observations of the zodiacal light are consistent with the measured results of the space detectors.
It has two symmetries
The distribution of interplanetary matter inevitably leads to two kinds of symmetry in the main part of zodiacal light:
1. Symmetric to the ecliptic plane;
2. Symmetric to the yellow circle passing through the sun.This has been fully confirmed by a large number of observations.
Brightness observation
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Ecliptic light
The brightness of zodiacal light increases monotonously towards the sun, which can be considered as an extension of the outer corona.In other words, near the sun, the zodiacal light melts into the F corona (dust corona) and becomes part of the outer corona.However, the brightness of zodiacal light is not fixed, it has short-term changes and long-term changes, and the reasons are very complex.For example, it has been pointed out that solar activity affects the brightness of zodiacal light.Of the night sky light that overlaps with the zodiacal lightnatureIt is also very complicated and changeable. In addition, it is necessary to distinguish between "true zodiacal light" (that is, the zodiacal light measured on the surface of the earth's atmosphere and corrected) and "zodiacal light" (that is, the zodiacal light changed by the scattering of the earth's atmosphere).It is difficult to deduce the true zodiacal light from the zodiacal light, and the uncertainty of the observation results mostly comes from this.
Poyntine Robertson effect will cause dust particles to enter the sun slowly in a spiral path, so there must be a steady stream of new dust particles to supplement the clouds in the ecliptic.Dust particles from the collision between comet dust tail and asteroid are the main source of particles that supplement the formation of zodiacal light and sunlight.In recent years, observations from different spacecraft have shown that there are indeed some dust particles with banded distribution that are related to some specific asteroid families and comet tails.
When the observation conditions are very good (for example, outside the earth's atmosphere), you can also see the zodiacal light extending tosunlightNearby, outwards almost covers the whole sky.It forms a bright belt along the ecliptic, called the ecliptic belt.The two sides of the ecliptic belt are parallel to the ecliptic. It extends from the top of the ecliptic light cone to the direction away from the sun, and its brightness continues to decline until it is about 135 ° away from the sun.After that, the brightness rose again and reached a maximum near the anti sun point.There is an area of about 20 ° × 10 ° light near the anti sun point, which is brighter than the surrounding area, called the sunshine.
The zodiacal light is a triangular cone along the ecliptic, like a tongue like dim light. The closer it is to the horizon, the more it expands and becomes brighter.In mid latitudes, it is usually easy to see near the eastern horizon after sunset in spring or before sunrise in autumn.The better viewing time is before the beginning of astronomical dawn (autumn) or after the end of astronomical twilight (spring).
The sunshine is the light image that appears at the place opposite to the sun and 180 degrees away,RangeIt is a small oval with a size of about 20 ° × 10 ° and a dim light, which is caused by the back scattering of sunlight through dust particles.It must be observed in an environment free from light damage and moonlight.
