Sorry, question 25, total solar eclipse

There are three kinds of eclipses: total solar eclipse, annular solar eclipse and partial solar eclipse. In the process of an eclipse, a total solar eclipse can be observed in some places on the central line of the food belt, and an annular eclipse can be observed in other places, so we call it a mixed eclipse, also known as the' fourth eclipse', which is the so-called' total solar eclipse'. [ 1]

catalogue

1 Introduction

2 Schematic diagram of the formation of total solar eclipse and annular solar eclipse

1 Introduction

"Through the clouds, we can only see part of the sunlight. The total lunar eclipse only lasted 14 seconds. Unfortunately, we didn't see' Phnom Penh'. " Yu Jun, an astronomical photographer who went to Ken to watch the eclipse, told the reporter, "The process of the eclipse is very short, and the feeling of being there is fleeting." [2]

Riquan huanshi

Total solar eclipse (two photos)

Starting from 3rd 19:05 Beijing time, the total lunar eclipse will be staged on the second day of this century. "The eclipse began at Beijing time 19:05, and the shadow of the moon began to project on the earth. The whole process lasted 3.3 hours. Because the shadow moves at different speeds on the earth's surface, the time for observing the solar eclipse varies from place to place. The longest total solar eclipse is located in the ocean near the west coast of Africa, but it is only 1 min 39 seconds. " Zhu Jin, director of the Beijing Planetarium, said. [2]

Why did this eclipse get so much attention? "The biggest attraction of this eclipse is that it is a rare total solar eclipse." Li Xin of Beijing Planetarium told reporters: "There are three kinds of solar eclipses: total solar eclipse, annular solar eclipse and partial solar eclipse. In the process of an eclipse, a total solar eclipse can be observed in some places on the center line of the eclipse belt, and an annular eclipse can be observed in other places, so we call it a mixed eclipse, also known as the' fourth eclipse'. " [2]

Li Xin said that if the distance between the Earth and the Moon is just right during the eclipse, the apparent diameters of the Sun and the Moon observed from the Earth will be almost equal. However, due to the movement of the moon and the curvature of the earth's surface, the distance between the earth and the moon will change slightly within a few hours of the eclipse, which is the reason for the mixed eclipse. There are three kinds of mixed food, which are the beginning and end of total food, the beginning and end of total food, and the end of total food is in the middle, but there will never be mixed food in the middle. This mixed food is the first case. [2]

Throughout the 20th century (190 1 by 2000), there were 228 eclipses, of which only 6 were mixed. There are only seven kinds of mixed foods in 2 1 century, and this one appeared on this year's1October 3, and it is the second mixed food in 2 1 century. At the beginning of this eclipse, an annular eclipse can be observed in the eclipse belt in the western Atlantic. Because the food fraction is very close to 1, you can only see the annular eclipse lasting 2 or 3 seconds. But this is the essence of mixed food. The annular eclipse with a food fraction close to 1 is very spectacular and is called "Phnom Penh solar eclipse". But this observable area is located in the ocean, so it is very difficult to observe. Then the eclipse turned into a total lunar eclipse, and the eclipse belt crossed the Atlantic Ocean, entered Central Africa and ended in East Africa. [2]

2 Schematic diagram of the formation of total solar eclipse and annular solar eclipse

Neither the earth nor the moon itself gives off light. Everything that doesn't shine and is opaque has a shadow behind it under the sunlight. The side of the earth and the moon facing away from the sun is also dragging long shadows. As we can see from the picture, the shadow consists of two parts: the darkest part of the shadow is called the umbra, and the sun can't be seen in the umbra of the moon; The slightly dim shadow around the umbra is called penumbra, and only a part of the sun can be seen in the penumbra of the moon.

The earth revolves around the sun, the moon revolves around the earth and revolves around the sun with the earth. Therefore, during the revolution of the moon around the earth (29 and a half days), when the moon moves between the sun and the earth, if the sun, the moon and the earth are in a straight line or close to a straight line, the sun will be covered and an eclipse will occur.

Similarly, when the moon comes to the earth's side facing away from the sun, if the sun and the earth's moon are in a straight line or close to a straight line, an eclipse will occur when the moon enters the umbra of the earth.

There are three kinds of solar eclipses: partial eclipse, annular eclipse and total solar eclipse. The part of the moon that covers the sun is called a partial solar eclipse. The moon only covers the central part of the sun, and a circle of the sun's surface is exposed around the sun, which is called annular eclipse like a halo. A total solar eclipse is when the sun is completely obscured. The occurrence of these three different solar eclipses is related to the changes of the positions of the sun, the moon and the earth, and also depends on the changes of the distance between the moon and the earth.

The moon is much smaller than the sun, its diameter is about a quarter of that of the sun, and the distance from the moon to the earth is almost a quarter of that from the sun to the earth, so from the perspective of the earth, the circular surfaces of the moon and the sun are almost equal in size, so they can be covered and an eclipse can occur. There is also a total solar eclipse [1]