Why is there a Leonid meteor shower?

In addition to the sun, nine planets and their satellites, asteroids and comets, there are a lot of dust particles and tiny solid blocks in the interplanetary space of the solar system, which also move around the sun. When approaching the earth, its orbit will change due to the gravity of the earth, so it is possible to pass through the earth's atmosphere. In other words, the earth may enter the earth's atmosphere when it crosses their orbit. Because these particles move at a high speed (1 1-72km/s) relative to the earth, they rub violently with atmospheric molecules and burn and glow, showing a light trace in the night sky. This phenomenon is called a meteor, which usually occurs at an altitude of 80- 120km above the ground.

Sometimes the number of meteors in a certain area of the sky will increase obviously in a certain period of time, with dozens or even more meteors per hour, which looks like rain. This phenomenon is called meteor shower. A particularly large meteor shower is also called star rain. For example, the Leonid meteor shower appears at 1833, with as many as 35,000 per hour (about 10 per second), and the scene is very spectacular. Meteor shower is the result of a large group of meteoroids breaking into the earth's atmosphere. This group of meteoroids is called meteor group.

The trajectories of meteor group members in space are basically parallel to each other. Because of the perspective, on the earth, meteor showers caused by meteor showers all radiate from the same point, which is called the radiation point of meteor showers. Most meteor groups are named after the constellation where the radiant point is located or the nearby stars, such as Leo meteor group and Aquarius δ meteor group.