What’s inside the sun?


Perhaps someone has heard such an interesting fact that the mass of our Sun is 99% of our entire solar system. The mass, volume and temperature of our star is simply staggering. Hence the simple question, what does the Sun consist of and what is in its center?

Of course, we cannot directly inspect and study the Sun from the inside. But the general laws of physics, the main characteristics of our star and theoretical models allow us to represent the internal structure of the Sun. The inner structure of the Sun helps us understand the structure of other stars like our Sun. Therefore, let’s look at it.

Let’s start our journey from the center of the Sun — its core. A sphere with a radius of about 150-175 thousand kilometers is called the solar core. It is here, at a depth of more than a million kilometers from the surface of the Sun, that the very thermonuclear reactions take place. The density of matter in the core is approximately 150 tons per cubic meter, which is 6.6 times the density of osmium, the densest metal on Earth. The temperature here reaches 14 million Kelvin.

Interestingly, the core is the only place in a star where energy is released (due to thermonuclear reactions). The rest of the Sun’s layers are simply heated by this energy.

The next layer of the inner structure of the Sun after the core is the zone of radiant transfer. Here, with the help of radiation, energy is transferred to the highest layer of the Sun — the convective zone. In the convective zone, the plasma is mixed and energy is transferred to the lower layer of the atmosphere — the photosphere. In the photosphere, matter cools down and sinks back into the depths of the convective zone, where over time it heats up from the zone of radiative transfer and rises again. The temperature in the zone of radiant transfer depends on depth and ranges from 7 to 2 million Kelvin. In the convective zone, the temperature drops to 6,000 Kelvin.

An interesting fact: the density of the convective zone layer is 1000 times less than the density of air on Earth. And if we decompose our entire Sun into molecules, then in we can see that in general the Sun consists of hydrogen and helium, by volume 92% and 7%, respectively. Also in the composition of the matter of the Sun there are other heavier elements, such as: iron, nickel, magnesium, chromium, carbon, sulfur and other elements. We can say that the Sun and other similar stars are made up of the entire periodic table.

As you can see, the internal structure of the Sun is diverse, but for scientists it is quite simple, in contrast to the Sun’s atmosphere.

In general, the Sun’s atmosphere can be divided into two layers: the photosphere and the chromosphere. The photosphere is the deepest layer of the Sun’s atmosphere and only it can be seen in the visible spectrum. And it is on it that sunspots are formed. This layer, relative to the solar radius, is very thin — up to 300 kilometers. The temperature in the upper layers of the photosphere drops to 4400 degrees Kelvin.

We talked about a fairly detailed structure of the chromosphere and its high temperature in this article — “Why is the solar corona so hot?”.

Author: Alexey Nimchuk.

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