Question

What causes a star to shine brightly

Answer 1

Deep inside the core of the sun, protons can collide into eachother with enough speed that they stick together to form a helium nucleus and generate a big amount of energy at the same time.

Answer 2

Stars shine brightly because they are hot and made up of gases. As we know that the fire gives off the light.

They are a source of energy and nuclear reactions continuously takes place there.

The best example is the sun which shines so bright because of the nuclear fission in it. the hydrogen is converted into helium continuously and this process emits heat and light.

So, the starts shines so bright.