How Stars Work

What happens in the radiative zone of the Sun?

The energy produced by nuclear fusion at the core of the Sun travels outward as radiation—photons traveling through the solar plasma. Although the photons travel at the speed of light, the plasma in a star is so dense that the photons keep running into particles and bouncing away in an unpredictable pattern called a random walk. The bouncing around is so extreme, that it takes an average of one million years for the solar light to travel the 250,000 miles (400,000 kilometers) through the radiative zone. In the vacuum of space, light can travel that distance in less than two seconds.


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