Just like our planet, and most other celestial bodies, the Sun is divided into distinct layers. The critical difference is that the Sun is not solid, unlike Earth, so the layers are a bit harder to determine. Because the Sun is mostly composed of helium and hydrogen and is not solid, it does not have an outer boundary that is clearly defined.
However, we can determine the internal structure of the Sun, and it is made up of seven different layers. The layers of the Sun are divided into two larger groups, the outer and the inner layers. The outer layers are the Corona, the Transition Region, the Chromosphere, and the Photosphere, while the inner layers are the Core, the Radiative Zone, and the Convection Zone.
The Outer Layers
- Transition region
There are four outer layers of the Sun, and the Corona is the outermost one. It starts at about 1300 miles above the photosphere, and its temperature is measured to be around 900,000 degrees Fahrenheit. It is impossible to see the Corona with the naked eye, but there is an exception. We are able to see it during a solar eclipse, or by using a special device called the coronagraph. There is no upper limit to the Corona.
It is followed by the Transition region, which is an extremely narrow layer that divides the Chromosphere from the Corona. Its width is only 60 miles, which is incredibly small for a layer on a body as large as the Sun. This layer marks the spot where the temperatures rise tremendously since the Corona layer is much hotter than the Chromosphere.
The Chromosphere is the layer we find between the distances of 250 and 1300 miles from the solar surface. The temperatures in this layer vary greatly, with the parts that are further from the solar surface being much hotter than the ones that are closer to it. Still, it does not compare to the temperatures that are reached in the Corona layer. It is an interesting thing to notice how the temperature in these layers grows the further away we move from the center of the Sun.
The Photosphere is the last, innermost layer of the outer layers of the Sun. We are able to observe this layer directly, and its temperatures vary between 11,000 and 6,700 degrees Fahrenheit. The majority of this layer is covered by granulation, which is caused by bubbling gases and sunspots from magnetic fields.
The Inner Layers
- Convection zone
- Radiative zone
There are three inner layers of the Sun, and the Convection zone is the outermost one. It completely surrounds the next layer, the Radiative zone.
In this layer, all of the hot material found near the center of the Sun rises cools down and drops back into the radiative zone to get more heat. This is the movement that creates sunspots and solar flares. This layer marks the border of what we usually refer to as the Sun.
The radiative zone is the second inner layer of the Sun. It sits outside of the core, and it holds its extremely high temperature. The zone itself has a temperature of around 7 million degrees Fahrenheit. This layer serves as a passage for all the energy that is released by the core. Photons travel through the radiative zone, and they can’t travel through long ranges of space, so it takes almost 50 million years for a photon to travel through this layer of the Sun.
Finally, we have the core, as the innermost layer of the Sun. The core is plasma, but its movement is extremely similar to that of a gas. The temperature of the core of the Sun is around 27 million degrees Fahrenheit. In the core, nuclear reactions occur that create helium from hydrogen atoms. This releases huge amounts of energy, and it starts to move outwards toward the other layers. This energy eventually becomes the light and heat we receive on Earth.