Internal Structure of the Sun

While we cannot physically observe the inside of the Sun, the principles of physics, key attributes of the Sun, and theoretical models enable us to conceptualize its internal structure. Gaining insight into the Sun’s internal makeup helps us comprehend similar stars in the universe. Let’s embark on this exploration starting from the core of the Sun.

The core, a sphere with a radius of approximately 150,000 to 175,000 kilometers, lies more than one million kilometers beneath the Sun’s surface. It is in this region that nuclear fusion reactions take place. Remarkably, the density in the core reaches about 150 tons per cubic meter, making it 6.6 times denser than osmium, the densest metal found on Earth. The temperature in this area soars to an astounding 14 million Kelvins.

Interestingly, the core is the sole area within the star that generates energy through nuclear fusion. This energy serves to heat the Sun's outer layers.

Following the core is the radiative zone, where energy is transferred to the upper layer of the Sun, known as the convective zone, primarily through radiation. Within the convective zone, plasma undergoes mixing, allowing energy to be conveyed to the lower atmospheric layer, the photosphere. In this region, the material cools and descends back into the convective zone, eventually heating back up from the radiative zone before rising once again. The temperature in the radiative zone varies with depth, ranging from 2 to 7 million Kelvins, while it drops to around 6000 Kelvins in the convective zone.

An intriguing fact: the density of the convective zone is about 1,000 times less than that of Earth’s atmosphere. If we could break down the Sun into its molecular components, we would find that it primarily comprises hydrogen (92%) and helium (7%), along with trace amounts of heavier elements such as iron, nickel, magnesium, chromium, carbon, and sulfur. In essence, the Sun contains nearly the entire periodic table.