Why doesn't it burn like the sun if Jupiter is made of hydrogen?

The requirement of nuclear fusion to occur is possessing enough mass to heat the core of the planet to 10,000 k. Jupiter's mass is too small to create nuclear fusion. Jupiter would need to be about seventy-five times as massive to fuse hydrogen, burn like the sun or become a star.

Jupiter is not big enough to react to the elements helium and hydrogen, which burn and cause it not to become bright, which is because there is no reaction to generate energy to burn. Jupiter is comprised of similar materials as the sun.