Among all kinds of meteor phenomena, the most beautiful and spectacular is the meteor shower. When it appears, thousands of meteors are like shining ribbons. Meteor shower is a kind of special celestial phenomenon in which groups of meteors appear to come from a point in the sky and fall. This point or a small area of the sky is called the radiant point of the meteor shower. A radiant point is a perspective effect. The basic reason for the formation of meteor shower is the fragmentation of comets. Comets are mainly composed of ice and dust. When the comet gradually approaches the sun, the ice vaporizes, so that dust particles, like water from a fountain, are ejected from the parent body and enter the orbit of the comet. However, large particles still remain around the mother comet to form a dust comet head; Small particles are blown away by the radiation pressure of the sun, forming a comet tail.
The remaining material remains near the comet's orbit. However, even a small eruption speed will cause a great difference in the revolution period of particles. Therefore, when the comet returns next time, the small particles will lag behind the parent, while the large particles will lead with the parent. When the earth passes through the dust tail orbit, we have a chance to see the meteor shower. Activity period of meteor shower: The five clouds of dust particles in the orbit of comets are called meteor clusters. When meteoroids can be ejected by comets, their distribution is relatively planned. Due to the gravitational action of the big planet, these particles gradually spread throughout the comet orbit. At present, this process is not very clear. Various forms of meteor showers may occur when the Earth passes through a meteoroid cluster. Every year the earth passes through the orbit of many comets. If there are meteoroid particles in the orbit, periodic meteor showers will occur. The meteor shower that occurs only when the mother comet moves to the perihelion is called near comet meteor shower. This indicates that the meteoroid cluster is still near the comet.
This type of meteor shower is mostly formed by comets with a period of less than several hundred years. Due to the gravitational perturbation of planets, the meteoroid body group of long-period comets may be very different from that of their parent comets. Meteor showers may also occur when the mother comet is not at the perihelion, which is called far comet type meteor shower. In order to distinguish meteor showers from different directions, the fate of meteor showers is usually given by the constellation of the sky region where the meteor radiation point is located.