The difference between solar eclipse and lunar eclipse

Eclipse means that the moon revolves around the earth and moves between the sun and the earth. If the sun, the moon and the earth are just in a straight line, the moon blocks the sunlight that hits the earth, and the shadow behind the moon just falls on the earth. At this time, the eclipse happened. People in the shadow of the moon on the earth began to see the sun gradually weakening, and the sun was covered by a circular shadow. When the sky is dark and completely covered, the brightest stars and planets can be seen in the sky. After a few minutes, the sun gradually emerged from the shadow edge of the moon and began to shine and make the last contact. Because the moon is smaller than the earth, only people in the shadow of the moon can see the solar eclipse. Total lunar eclipse occurs when the moon blocks all the sun, partial solar eclipse occurs when the moon blocks part of the sun, and annular solar eclipse occurs when the moon blocks the central part of the sun. The duration of the total solar eclipse shall not exceed 7 minutes 3 1 sec. The longest time of annular eclipse is 12 minutes and 24 seconds. In order to postpone the observation of the total solar eclipse, a French astronomer chased the shadow of the moon by supersonic plane and extended the observation time to 74 minutes. China has the oldest solar eclipse record in the world, and there have been exact solar eclipse records for over 0/000 years BC. A solar eclipse is a typical example of light traveling in a straight line in a celestial body. When the moon moves between the sun and the earth, it is not always like this. When a lunar eclipse occurs, two conditions need to be met. First of all, the solar eclipse always happens on the first day of the lunar calendar. Not all eclipses will happen on the first day of the lunar calendar, because the orbit of the moon (ecliptic) and the orbit of the sun (ecliptic) are not on the same plane. There is an included angle of 59 between the ecliptic plane and the ecliptic plane. On the first day, if both the sun and the moon move near the intersection of the ecliptic and the ecliptic, and the sun and the intersection form a certain angle (eclipse limit), an eclipse will occur, which is the second condition to be met.

Because the orbits of the moon and the earth are not perfect circles, and the distance between the sun and the moon is near or far, the shadow formed by the sun being blocked by the moon can be divided into umbra, pseudo-umbra (formed when the moon is far away from the earth) and penumbra on the earth. The observer can see the total solar eclipse in the umbra; Annular eclipse can be seen in the range of pseudoumbra; Only a partial solar eclipse can be seen in the penumbra.

When the total solar eclipse occurs, it can be divided into five eclipse images according to the positional relationship between the round surface of the moon and the round surface of the sun: 1. Initial loss. The moon moves faster than the apparent speed of the sun. The moon caught up with the sun during the eclipse. When the eastern edge of the moon just "touches" the western edge of the sun, it is called the first loss, which is the first "circumscribed" and the beginning of the solar eclipse. 2. Eat well. About an hour after the initial loss, the moment when the eastern edge of the moon "cuts in" with the eastern edge of the sun is called an eclipse, which is the beginning of the total solar eclipse, when the moon covers the whole sun; 3. Eat a lot. It is the deepest eclipse moment of the sun, and the center of the moon moves to the center closest to the sun; 4.light. The moment when the western edge of the moon and the western edge of the sun "cut in" is called light, which is the end of the total solar eclipse; It usually takes only two or three minutes from eating to lighting, and the longest is no more than seven and a half minutes; 5. Last contact. About an hour after the birth of light, when the western edge of the moon "touches" the eastern edge of the sun, it is called the last contact. Since then, the moon has completely "left" the sun, and the eclipse is over.

There are many mountains on the surface of the moon, and the edge of the moon is irregular. At the moment of the lunar eclipse or the arrival of light, when the valley on the edge of the moon fails to completely cover the sun, the uncovered part forms a luminous area, like a crystal diamond; The reddish aperture around constitutes the "ring" of the diamond ring, which looks like a diamond ring inlaid with bright gems. Sometimes a lot of particularly bright lights or spots are formed, like a string of pearls embedded around the sun. This phenomenon is called Bell Pearl (Belle is a French astronomer).

Whether it is a partial solar eclipse, a total solar eclipse or an annular solar eclipse, the time is very short. The area where the solar eclipse can be seen on the earth is also limited, because the moon is relatively small and its umbra is relatively small and short, so the umbra will not sweep the earth for a long time. Because the average length of the umbra of the moon (373,293 kilometers) is shorter than the average distance between the moon and the earth (384,400 kilometers), there are more annular eclipses on the whole earth than total solar eclipses. solar prominence

Prominence is a kind of solar activity phenomenon that protrudes beyond the edge of the sun's surface. When prominence appears, colored balls in the atmosphere resemble burning grasslands, and rose-red tongue-shaped gas rises like fire, with different shapes, some like clouds, some like arch bridges, some like fountains, some like clumps of grass, and some are as beautiful as festive fireworks. On the whole, they are shaped like earrings attached to the edge of the sun, hence the name "prominence". Prominences rise about tens of thousands of kilometers. Large prominences can be hundreds of thousands of kilometers higher than the surface of the sun, with a general length of about 200,000 kilometers, and individual prominences can reach 1.5 million kilometers. Prominences are much darker than the photosphere, so they can't be observed with the naked eye at ordinary times, and can only be seen directly during a total solar eclipse. Prominence is a very strange phenomenon of solar activity. Its temperature ranges from 5,000 to 8,000. Most prominences rise to a certain height and then slowly land on the surface of the sun. However, some prominences float in the lower layer of the corona, and the temperature is as high as 2 million K, which is as strange as a piece of unmelted ice in a hot steelmaking furnace. In addition, the density of prominence is 654,330 higher than that of corona.

solar corona

The outermost atmosphere of the sun is called the corona. The corona extends several times to dozens of times the diameter of the sun. In the most active year of solar activity, the corona is close to a circle; In quiet years, it is oval.

B] There are large irregular dark areas in the corona, which are called coronal holes. Coronal hole is an area with low gas density in the corona. There are three kinds of coronal holes: polar coronal holes, isolated coronal holes and extended coronal holes. Solar energy loses material in the form of solar wind-material particle flow. Coronal hole is an important source of high-speed solar wind. Coronal mass ejection (CME) is a very macroscopic and huge material and magnetic field structure that occurs in the corona. It is a sudden explosion phenomenon of large-scale dense plasma. Nothing can affect the earth more than it. When there is a strong explosion and coronal mass ejection on the sun, the powerful plasma flow carried by the solar wind may reach the polar regions of the earth. At this time, the aurora appears at the poles of the earth. The forms of aurora are ever-changing. Aurora has also been found on some planets with magnetic fields in the solar system. Flares occurring in the corona are called X-ray flares, and their wavelength is only 1 ~ 8 Angstroms or less. It directly causes the disturbance of the earth's ionosphere, thus affecting the earth's short-wave communication.

Rilang

An ejection phenomenon of solar photospheric matter. It usually occurs over sunspots and has strong reproducibility. When a broken wave falls behind along the rising path, it will trigger a new broken wave to take off, and so on, but the scale and height are getting smaller and smaller every time until it disappears. Surfing at the edge of the sun looks like a bright hill with a sharp peak at the top. The height of the rise is different. Small surfing is only a few hundred kilometers, big surfing can reach 5000 kilometers, and the maximum surfing can reach 1 ~ 20000 kilometers. The maximum speed of the projectile can reach 100 ~ 200 kilometers per second, which is more than 100 times faster than the fastest reconnaissance plane. When they reach the highest point, they begin to descend under the influence of the sun's gravity until they return to the surface of the sun. From the high-resolution observation data, it is found that surfing is composed of a very small bundle of fibers, and the distance between each fiber is very small. They shine together and move together as a whole.

Solar activity forecast

The change of the state of space environment between the sun and the earth is becoming more and more important to the modern cutting-edge technology on which modern life and production depend. As mentioned earlier, X-ray flares directly cause ionospheric disturbances on the earth, thus affecting short-wave communication on the earth. Solar proton events will endanger the sensors and control equipment of astronauts and spacecraft, and also pose a radiation threat to passengers and crew flying at high latitudes. According to statistics, strong solar activity is related to earthquakes, volcanic eruptions, droughts and floods, heart and nervous system diseases and traffic accidents. Therefore, solar activity and solar-terrestrial physical prediction are very important. Solar activity forecasting is divided into long-term, medium-term and short-term forecasting and early warning. As a systematic scientific research object, the space environment of the sun and the earth began in 1957 when humans entered space. The 1950s and 1970s were the exploration stages, and people gradually realized the importance of space environment. On the basis of a lot of exploration, a static model describing the environment is established and some important spatial activities are predicted. After 1980s, driven by demand, the research on the space environment of the sun and the earth developed rapidly. Since 1979, the international conference on solar-terrestrial prediction has been held as scheduled every four years, and its scale has been expanding. In order to unite and coordinate the work of major countries, a joint forecasting center was established. Headquartered in the United States, there are 10 regional alarm centers distributed all over the world. Our Beijing alarm center is one of them. After entering the 1990s, scientists vividly called it "space weather".

Solar activity cycle

The average period is 22 years, and it includes two sunspot cycles of 1 1 year. In each cycle, the polarity of sunspots is opposite, and the changes of other solar phenomena have two highs and two lows like sunspots. These solar phenomena include prominence, flare and frequency fluctuation of magnetic effect, and magnetic effect includes aurora and enhancement of radio interference to the earth. The basic sunspot cycle (sometimes called solar activity cycle) of1year was announced by Schwabe in 1843. Some people try to link the solar activity cycle with the changes of other phenomena, such as small changes in the diameter of the sun. Even the change of tree rings is related to the solar cycle.

A sunspot is a sunspot.

On the photosphere of the sun, there are some swirling airflow, such as a shallow disk, which is concave in the middle and looks black. These rotating air currents are sunspots. Sunspots themselves are not black. The reason why it looks black is that its temperature is one or two thousand degrees lower than that of the photosphere. Against the brighter photosphere, it becomes a black spot with no light.

Sunspot is a kind of solar activity on the photosphere, and it is the most basic and obvious phenomenon in solar activity. It is generally believed that sunspots are actually a huge vortex of hot gas on the surface of the sun, with a temperature of about 4500 degrees Celsius. It looks like some black spots because it is lower than the surface temperature of the photosphere of the sun. Sunspots rarely move alone. Often appear in groups

In ancient times, people did not understand the scientific truth of solar eclipse, and the fear of solar eclipse was no less than that of solar eclipse. It is said in foreign countries that Columbus sailed to Jamaica in South America at the beginning of the16th century, and there was a conflict with the local aborigines. Columbus and his sailors were trapped in a corner, without food and water. The situation is very critical. Knowing that there would be a total lunar eclipse that night, Columbus, who knew something about astronomy, shouted to the natives, "No food, no moonlight!" " In the evening, Columbus's words came true, and there was no moonlight. When the natives saw this scene, they were afraid, so they quickly made peace with Columbus. Eclipse is a special astronomical phenomenon, which means that when the moon moves to the shadow of the earth, the area between the moon and the earth will be blocked by the earth because of the sunlight, and the moon will be missing. That is to say, at this time, the sun, the earth and the moon are just (or almost) in a straight line, so the light from the sun to the moon will be blocked by the earth. As far as the earth is concerned, when an eclipse occurs, the directions of the sun and the moon will be different by 180 degrees, so the eclipse must occur in Wangwang (that is, around the lunar calendar 15). It should be noted that the orbits of the sun and the moon in the sky (called the ecliptic and the ecliptic) are not on the same plane, but have an intersection angle of about 5 degrees, so only when the sun and the moon are located near the intersection of the ecliptic and the ecliptic can they be connected in a straight line to produce an eclipse.

Eclipses can be divided into three types: partial eclipse, total eclipse and penumbral eclipse. When only a part of the moon enters the umbra of the earth, there will be a partial lunar eclipse; When the whole moon enters the umbra of the earth, a total lunar eclipse will occur. As for the penumbral eclipse, it means that the moon just passes through the penumbral region of the earth, which causes the brightness of the moon to be extremely slightly weakened, so it is difficult for the naked eye to see the difference, so it is not noticed by people.

The diameter of the earth is about four times that of the moon. In lunar orbit, the umbra diameter of the earth is still 2.5 times that of the moon. So when the centers of the earth and the moon are roughly on the same straight line, the moon will completely enter the umbra of the earth, resulting in a total lunar eclipse. But if only a part of the moon is always covered by the umbra of the earth, that is, only a part of the moon enters the umbra of the earth, a partial lunar eclipse will occur. There will be no annular eclipse on the moon. Because the moon is much smaller than the earth.

The diameter of the sun is much larger than that of the earth, and the shadow of the earth can be divided into umbra and penumbra. If the moon enters the penumbra, the sunlight will also be blocked. This phenomenon is called penumbral eclipse in astronomy. Because the sun in the penumbra is still very strong, the brightness of the lunar surface is only slightly weakened. In most cases, the penumbra eclipse is not easy to distinguish with the naked eye. In general, because it is not easy to be found, it is not called an eclipse, so there are only two kinds of total solar eclipse and partial solar eclipse.

In addition, because the umbra of the earth is much larger than that of the moon, it also means that in the event of a total lunar eclipse, the moon will completely enter the umbra of the earth, so there will be no annular eclipse.

The number of solar eclipses occurs twice a year, up to three times, and sometimes none at all. Because under normal circumstances, the moon either passes above the Earth's umbra or leaves from below, rarely or partially passes through the Earth's umbra, so an eclipse will not occur under normal circumstances.

According to the statistics of observation data, the percentage of lunar eclipse, partial eclipse and total eclipse in the penumbra in each century is about 36.60%, 34.46% and 28.94%.

After the total lunar eclipse, the penumbra begins to eclipse: the moon just touches the penumbra, which is invisible to the naked eye at this time.

The process of a formal eclipse can be divided into five stages: initial loss, eclipse, eclipse, luminescence and last contact.

The first loss: marks the beginning of the solar eclipse. The moon slowly entered the shadow from the eastern edge, and the umbra of the moon and the earth was delineated for the first time.

Eclipse: The western edge of the moon is inscribed with the western edge of the Earth's umbra, and the moon just enters the Earth's umbra.

Eclipse: The center of the moon is closest to the center of the Earth's umbra.

Luminescence: the eastern edge of the moon is inscribed with the eastern edge of the umbra of the earth, and the total solar eclipse phase ends at this time.

Final contact: the western edge of the moon is tangent to the eastern edge of the umbra of the earth. At this time, the whole eclipse was over.

The degree of eclipse is called "eclipse", which is equal to the ratio of the farthest distance from the edge of the moon wheel to the umbra of the earth and the meridian of the moon when the eclipse is serious.

End of the penumbra eclipse: The moon leaves the penumbra, and the whole eclipse process officially ends.