What's Inside a Star

Sun Star Photosphere Fusion Nuclear Image

A star at its most basic, is a burning ball of gas. A very large, hot, massive burning ball of gas. Our closest example is, of course, the Sun, which teaches us much of what we know of the makeup of a star. What do we find when we explore inside this burning ball of gas?

A Look Inside a Star

As much as we know about the stars in the universe there is quite a lot we don’t know. Using our life giving star, the Sun, as an example, we can predict what goes on inside most stars, however.

Starting from the centre outwards, a star is really a constantly renewing source of energy. It is not infinite, although in comparison to the lifespan of a human it may seem so, but after several billion years even a star will burn out. Until that time, however, a star is very much like a series of nuclear explosions, creating energy through a process called nuclear fusion.

The core of a star converts hydrogen into helium through the P-P Chain, which stands for Proton- Proton. This is part of the nuclear fusion process, and the core is also the only part of a star that actually produces heat (because of the fusion process). The rest of the star is heated because of the core heat radiating outwards.

How it keeps going

The core of a star is a self monitoring entity, keeping the fusion rate at a relative constant due to a self-correcting equilibrium process that modulates the density and temperature. These two factors have a great impact on the rate of fusion that takes place—if the rate of fusion were to ramp up, the core would heat up more and expand against the outer layers. This would cause the fusion rate to slow down. If, conversely, the fusion rate drops too low, the core would cool enough to shrink. Once it shrank past a certain level this would cause the fusion process to ramp up once more. In this way the fusion rate stays roughly in the right window of temperature and density to continue as it is.

Slow Moving Traffic

A star is a fine example of the scale of the universe. The sun provides life on Earth daily energy and heat from the giant ball of gas that is in a constant state of action, but when considering the length of time it takes from the creation of energy to its delivery on the planet’s surface it really helps put things in perspective.

When the energy—in the form of photons released in a fusion reaction in the core—is created it is immediately absorbed by a nearby area of solar plasma. It is then re-emitted in a completely random direction. It continues this process until it makes its way up through the radiation level of the star and then out into the photosphere and beyond. The process is so random, and the star so vast, that in our Sun it takes that photon about 50 million years to escape. Even if the random travel of the photon keeps it travelling in a relative straight line outwards it would take around 20,000 years.

Final Thoughts

Understanding the processes and make up of a star’s interior is a very important step in understanding its impact on the neighbourhood. Modelling the nuclear fusion process of a star has been instrumental to terrestrial scientists in their pursuit of new, safe, renewable power sources.

What's Inside a Star

A Look Inside a Star

How it keeps going

Slow Moving Traffic

Final Thoughts

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