The origin of the name of meteor shower

Meteor showers are generally thought to be caused by the friction between meteoroids and the earth's atmosphere (meteoroids can be asteroids in the asteroid belt). Meteor swarms are often produced by fragments of comets, so the orbits of meteor swarms are often related to the orbits of comets. Meteor showers are formed by swarms of meteors. A meteor shower looks like a falling meteor in the night sky. This point or this small sky area is called the radiation point of meteor shower. Meteor shower is usually named after the constellation in the sky where the radiant point of meteor shower is located to distinguish meteor showers in different directions. For example, every year165438+1October 1 7 or so, the radiant point of the meteor shower is in Leo, so it is named Leonid meteor shower. Orion meteor shower, Aquarius meteor shower and Perseid meteor shower are also named in this way. A single meteor is random in direction and time, and there is no radiation point at all. This kind of meteor is called accidental meteor. An important feature of the essential difference between meteor shower and accidental meteor is that the reverse extension lines of all meteors intersect at the radiation point. The earliest meteor shower record in the world is China's record of Lyra meteor shower: "Stars fall like a rainy night". "Zuo Zhuan" records that in the seventh year of Duke Zhuang of Lu, "in summer and April, the stars disappear and fall like rain." An earlier ancient book, Annals of Bamboo Books, wrote: "In the fifteenth year of Xia Emperor, the stars set like rain at night."

Meteor shower [2] In the solar system, besides the eight planets, dwarf planets and their satellites, there are comets, asteroids and some smaller celestial bodies. Although small in size, small celestial bodies revolve around the sun like the eight planets and dwarf planets. If they have a chance to pass near the earth, they may break into the earth's atmosphere at a speed of tens of kilometers per second. Due to the intense friction with the earth's atmosphere, huge kinetic energy is converted into heat energy, which ionizes the matter and gives off dazzling light. This is the meteor that we often see.

Some meteors are single, the direction and time are random, and there are no radiation points at all. This kind of meteor is called accidental meteor. Meteor showers are essentially different from occasional meteors. An important feature of meteor shower is that the reverse extension lines of all meteors intersect at the radiation point.

The scale of meteor showers varies greatly. Sometimes only a few meteors appear in an hour, but they all seem to "flow out" from the same radiation point, so they also belong to the category of meteor showers; Sometimes in a very short time, thousands of meteors can be seen at the same radiation point, just like fireworks in festivals. When the hourly zenith discharge (ZHR) of meteor shower exceeds 1000, it is called "star rain".

Occasional meteors are produced every day, and the time and area of occurrence are random. Meteor showers are periodic in time, and some of them can be predicted scientifically, so they are also called periodic meteors. In addition, it is an important feature of meteor shower that all backward extension lines intersect at the radiation point.