The different layers of the Sun are determined by the physical function they perform. Currently, astrophysics has a model of the solar structure made up of six layers divided into two groups: the inner and outer layers of the Sun.
The only layers of the Sun that can be observed directly are the outer layers: photosphere, chromosphere, and corona. These three layers make up the solar atmosphere.
Starting from an inner core and moving outward, the layers of the Sun are:
1. Solar Core
The core of the solar Sun is the layer where nuclear fusion reactions are generated. Therefore, it is where all the energy is generated. It is composed of gas that appears as a plasma due to high temperature (about 15 million degrees Celsius) and pressure due to its own magnetic field. High pressure is necessary for nuclear fusion to occur.
Nuclear reactions are the source of energy generating more energy than 80% of the other stars in the Milky Way.
Thermal energy has been transmitted through electromagnetic waves for 4,603 billion years. This phenomenon of electromagnetic waves is solar radiation.
2. Radiant Zone of the Sun
In the area outside the solar core, the transport of the energy generated inside is produced by radiation to the radioactive area. This zone is composed of plasma, that is, large amounts of ionized hydrogen and helium.
In this area, the temperature decreases as we move away from the nucleus. These temperature differences favor the photons moving outwards.
3. Convective Zone of the Sun.
Located above the radiant area. Solar gases are no longer ionized and photons are easily absorbed. Consequently, the photons are no longer transported by radiation.
The transport of energy is carried out by convection. Heat is transported in an inhomogeneous and turbulent manner by the fluid itself.
Turbulent convective sections are formed, in which patches of hot and light gas rise up to the photosphere. In the photosphere the solar atmosphere becomes transparent to radiation and the hot gas gives up its energy in the form of visible light.
The photosphere generates almost all of the visible light that the star emits into space. The photosphere is the first of the outer layers of the Sun.
In the photosphere, sunspots (7) are formed, which are dark spots on the solar surface due to their much lower temperature. Most solar flares (9) appear around sun spots.
The width of the photosphere is approximately 400 kilometers, and the temperature varies between 7,500 and 4,700 Kelvin, decreasing as it moves away from the nucleus.
The chromosphere is believed to be 2,000 to 3,000 kilometers wide. As it moves away from the nucleus, the density of the chromosphere decreases and the temperature increases from 4,500 to 100,000 degrees Celsius.
6. Crown, the Outer Layer of the Sun.
Its width is a few million kilometers. The total luminosity is only half the luminosity of the full moon.
The density of matter at the base of the corona is 109 atoms per square centimeter.
The temperature of the corona generally oscillates around one million kelvins.