The interior of the Sun is divided into several spherical shells: the core, the radiation zone, and the convective zone. The core is located in the center of the Sun and is the place for the nuclear fusion of hydrogen into helium. The radiation zone is located above the core and is responsible for the upward energy transfer due to radiation. The convective zone is located in the outer layer of the inner part of the Sun and is accountable for sunspots and solar flares.
The Sun’s outer layers consist of the corona, the transition region, the chromosphere, and the photosphere. The photosphere is the layer we see during solar eclipses and contains various chemical elements such as hydrogen, helium, carbon, and oxygen.
The inner layers of the Sun are of great importance for understanding its physical processes and characteristics. Unraveling the mystery of the inner part of the Sun involves studying the aspects of these main layers, each of which has its unique properties.
Image created by Lee H. Kolb, audiovisual engineer at NASA/Marshall Space Flight Center
The sun consists mainly of gaseous material and can be divided into several main layers:
Core: The central layer of the Sun, known as the core, is where the primary process that powers our star occurs – the nuclear fusion of hydrogen into helium. In this reactor, the temperature reaches about 15 million degrees Celsius, and the pressure is so great that the core is compressed, creating a powerful thermonuclear process.
Outer nuclear layer: This layer is located behind the core and represents the zone where the energy synthesized in the core begins to move upwards towards the surface of the Sun. This process, known as convection, causes ripples and thermal flares, known as solar flares. Outer reddened layer (photosphere): The photosphere is the layer of the Sun closest to the surface and is the layer we see during solar eclipses. This layer contains various chemical elements such as hydrogen, helium, carbon, and oxygen and emits light due to heating.
Corona: The corona is the Sun’s outer layer, the least warm but the brightest. This layer is visible during solar eclipses when its pale glow extends beyond the visible photosphere.
The composition of the Sun consists mainly of two chemical elements:
Hydrogen (~73% mass and ~92% volume): Hydrogen is the main element that fuels reactions in the Sun’s inner core. Most of the hydrogen in the Sun is converted into helium through nuclear fusion.
Helium (~25% mass and ~7% volume): Helium is formed due to the nuclear fusion of hydrogen in the core of the Sun. It makes up a significant part of the mass of the Sun and is responsible for many phenomena observed on the surface.
Other elements such as iron, nickel, oxygen, nitrogen, silicon, sulfur, magnesium, carbon, neon, calcium, and chromium are also found in the Sun, but in smaller amounts (less than 2% by mass).
The sun generates a huge amount of energy, which is the source of light, heat, and other forms of energy for all objects in the solar system. Solar radiation reaches the Earth and is critical to life on our planet, including photosynthesis and climate phenomena.
The Sun is classified as a G-type main-sequence star.
The Sun emits photons and neutrinos. Photons emitted by the Sun carry the energy and light we perceive on Earth. This light is the source of heat for sustaining life on Earth. Neutrinos are elementary particles emitted by the Sun during nuclear fusion. Neutrinos have very little mass and almost no charge, so they fly through matter almost without interaction. Since neutrinos fly through the Sun and other objects without significant interference, they are an essential source of information about nuclear processes occurring in the solar core.