How Can Stars Shine?
Star is a very large ball of burning gas in space which is usually seen from earth as a point of light in the sky at night. But, not all of the stars can only be observed at night, such as sun which is known as the nearest star to the earth.
If we see stars, we will think that stars have their own light. Now, how can they shine? Generally, the stars can shine because of thermonuclear fusion.
The thermonuclear fusion starts because of the intense pressure and temperature at the core of the star. In this place, atoms of hydrogen are fused into atoms of helium. And this reaction can releases energy in the form of gamma rays. And then, the gamma rays are trapped inside the star and push outward against the gravitational contraction of the star. Then, the gamma rays try to get out from the star. They are absorbed by one atom, and then emitted again. This can happen many times in a second and a single photon can take 100,000 years to reach the surface.
Then, when the photon reaches the surface, they have lost some of their energy so they become visible light photons. These photons leap off the surface and head out in a straight line into space. They can travel all the time if they run into nothing.
So we can see beautiful shining stars in the sky.