Why are there stars at night?

Because the light of the sun is very strong and the light of the stars is very weak during the day, you can't see the stars during the day. But in fact, the stars exist like night.

Stars can be roughly divided into planets, stars, comets, white dwarfs and so on.

1, the planet itself doesn't shine, what we see is the sunlight it reflects.

2. A star is a big celestial body like the sun, which will react inside itself and radiate energy into space in the form of light.

3. Comets are like Halley's Comet. The light we see is the phenomenon that the material of the comet's tail is melted when it passes through the solar system, so the comet we see often has a long tail. Most of the stars we can see at night are stars, and some are planets in our solar system.

Extended data:

Without external force, under the action of universal gravitation, all objects tend to gather towards the center. The most concentrated result is a sphere! Although a star is solid on the surface, it is possible to transform it into a sphere, because solids are also deformable and solid particles are movable.

The energy activity inside the star makes the shape of the star irregular. However, the stones in the mountains roll down from the heights due to the gravity of the stars, and the rivers carry the sediments from the heights to the low-lying oceans (rivers also flow due to the gravity of the stars). These are all examples of concentration to the center, which make the star change from irregular to spherical. If the interior of the star stops moving, it is likely that the star will become a very standard sphere (except for centrifugal force and gravity of other celestial bodies) after many billions of years.

Many asteroids, because of their small mass and low gravity, are generally composed of hard solid rocks, and it is difficult to complete the process of moving to the center under the action of their own gravity, so their shapes are grotesque, oval and rod-shaped.