Students, do you know why the stars in the sky flash? I found the answer from "One Hundred Thousand Why". It turns out that before starlight shines into our eyes, it must pass through the earth's atmosphere. The atmosphere is volatile, and the temperature and density of each layer of atmosphere are different. As a result, the degree of refraction of light is also different.
Before the starlight reaches the ground, it will undergo many refractions, sometimes converging and sometimes dispersing. It is this turbulent atmosphere that makes us feel the stars twinkle when we look at them, just like blink of an eye. If you take a spaceship to watch the stars, the stars will not twinkle at all.
I also know why some stars in the sky are bright and some are dim: some stars in the sky are dark and some are bright. In addition to its luminous intensity, there is another factor that determines the brightness of stars, which is the distance between stars and us. Generally speaking, the stars look brighter and brighter as they get closer to us.
The apparent brightness of stars is expressed by the apparent magnitude. The brightest stars we see are generally rated as first class stars, and the darkest stars that people with normal vision can barely see with the naked eye are rated as sixth class stars.