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What Is the Sun Like? Structure and Origin

What is the Sun like? Structure and origin

The Sun is a star around which the Earth rotates. It is mainly composed of the chemical elements hydrogen and helium.

It has an approximate diameter of 1,400,000 km and a mass of 1.99 × 1033 g. Inside it could be placed 1.3 million Earth planets.

The Sun revolves around itself. However, since it is made up of a large mass of gases, the different regions do not rotate in solidarity, but they do so at different speeds, depending on latitude.

The Sun, and with it the entire solar system, moves towards a point in the sky located in the Hercules constellation at a speed of about 19 km / s.

What Kind of Star Is the Sun?

Our sun is a yellow dwarf, a medium-sized star. This type of star has an average surface temperature of about 6,000 degrees Celsius and its brightness is light yellow, almost white.

Scientists believe that the sun is in the middle of its life. When it grows old it will become a red giant and later it will become a white dwarf.

Our star is estimated to be brighter than 85% of the billions of stars in the Milky Way. Most are red dwarfs.

Features and Data

Average distance from Earth

149.597.870.700 m


1.391.016 km


6,0877 x 10 12 km 2


1,4123 x 10 18 km 3


1,9891 × 1030 kg


1411 kg / m 3

solar Structure

The Sun is made up of:

  1. Solar core.
  2. Radiant zone.
  3. Convective zone.
  4. The photosphere. Inner layer.
  5. The chromosphere. Intermediate layer.
  6. The crown. Outer layer.

the Sun

The only ones that can be observed directly are the external ones, which are called photosphere, chromosphere and corona. These three layers make up the solar atmosphere. 

The transition from the properties of one layer to those of the next takes place gradually.

Solar Core, the Origin of Energy

The solar nucleus is the source of solar energy. In the nucleus it reaches the highest temperature (around 15 million degrees). It is made up of gas that appears as a plasma.

Inside, nuclear fusion reactions occur. These nuclear reactions are responsible for the production of solar energy. The rest of the star is heated by heat transfer from the core.

Every second, the core transforms approximately 600 million tons of hydrogen into helium. This nuclear reaction releases a large amount of energy. 3.86 × 10 26 J / s.

The density of the nucleus is close to 150,000 kg / m 3 (150 times denser than liquid water).

Radiant Zone

In the area outside the nucleus, the transport of the energy generated inside occurs by radiation to the outer limit of the radioactive area. This zone is made up of plasma, that is, large amounts of hydrogen and ionized helium.

The Sun's temperature decreases from the inside out. Therefore, it is easier for a photon to move outwards than the other way around. It can take a million years for a photon to reach the surface and manifest as visible light.

Convective Zone

Located above the radiant zone. Solar gases are no longer ionized and photons are easily absorbed. Consequently, photons are no longer transported by radiation.

The energy transport is carried out by convection. Heat is transported in an inhomogeneous and turbulent way by the fluid itself.

Turbulent convective sections form, in which patches of hot, light gas rise 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.

Photosphere, the Innermost Layer

The photosphere is the innermost layer and is responsible for almost all of the visible light that the star emits into space.

The width of the photosphere is approximately 400 km, and the temperature varies between 7,500 kelvin and 4,700 kelvin, to the areas furthest from the nucleus.

Chromosphere, Intermediate Layer

The chromosphere is believed to be 2,000 to 3,000 km wide. The density of the chromosphere decreases from the innermost to the outermost regions, but the temperature increases from 4,500 to 100,000 degrees Celsius at the same time.

Crown, Outer Layer

Its width is a few million kilometers. The total brightness is only half the brightness of the full moon.

The density of matter at the base of the corona is 109 atoms / cm2. This value is equivalent to 10-10 times the density of the Earth's atmosphere at sea level.

The temperature of the corona generally ranges around one million kelvins.

What Are Sunspots?

Sunspots are relatively dark spots on the sun's surface. They are associated with relatively cooler points in the sun. This relative cooling caused by strong magnetic fields hinders the convection of the plasma.

The heat supply from the core is temporarily reduced. Sunspots disappear over time.

Sunspot number is a measure of the Sun's activity. An active sun produces short bursts of energy that release charged particles.

What Are Solar Flares?

A solar flare is basically a giant explosion on the surface of the Sun. It occurs when the magnetic field lines of sunspots get tangled and erupt.

The material heats up to many millions of degrees Celsius in just minutes. Radiation is emitted through virtually the entire electromagnetic spectrum.

Solar flares are frequent when the Sun is active in the years around the solar maximum. Some solar flares can launch huge clouds of solar plasma into space. These eruptions are called coronal mass ejections.


The sun is the main source of energy for our solar system.

The most important part is the core. Nuclear fusion reactions are generated in the nucleus, releasing a large amount of energy.

The most important layers are:

  • The photosphere. Inner layer.
  • The chromosphere. Intermediate layer.
  • The crown. Outer layer.

Published: November 9, 2016
Last review: May 14, 2020