How big is the sun and why

The structure of the sun

We explain the structure of the sun to you and imagine the sun as an onion - a look into the interior of our central star.

The sun: the oldest and largest star in our solar system

Our sun is a self-luminous sphere made of hot gases which, unlike the earth, has no fixed mass. With a diameter of 1.4 million kilometers, our gigantic fireball is not only the largest celestial body, but also the heaviest.

Compared to the sun, our earth looks tiny with a diameter of 13,000 kilometers. Imagine that the sun is a soccer ball and the earth is a three millimeter ball about 30 meters away from the soccer ball. This is roughly the relationship between the sun and the earth. But although the sun is 330,000 times heavier than our earth, it is not sluggish.

In 25 days, the sun rotates once around itself and at the same time races through the Milky Way at hell's speed. The sun moves around the center of the galaxy, our solar system, at around 220 kilometers per second. Inside, there are barely imaginable temperatures of 15 million degrees Celsius for us humans and the pressure is 200 billion times higher than on earth.

The core of the sun - a fusion reactor

If we take a closer look at the sun, we can see that the structure of the sun is similar to that of an onion: It consists of several layers and skins. The core of the sun has a gigantic diameter of about 175,000 km and is a fusion reactor.

Nuclear fusion takes place here at a temperature of 15 million degrees Celsius and ten times the density of lead. A heavy helium nucleus is created from four hydrogen atomic nuclei. During this amalgamation, mass is lost, which is converted into energy.

In just one second, the sun converts around five million tons of matter into energy, which it releases into the room in the form of heat and light. The most important properties of the sun come from this loss of mass: light and warmth.

The long way through the radiation zone

The radiation zone is located around the core of the sun. Here the energy from the inside of the sun is transported to the outside in the form of light. However, this layer is so dense and impenetrable that light and heat need a million years to get to the outside, even at the speed of light. So when the sun's rays reach our earth, they are already ancient.

Glowing chunks on the way to the sun's surface

If we move further away from the core of the sun, the temperature drops to "only" three million degrees Celsius and we reach the next layer - the convection zone. The following happens there: Due to the "low" temperature, the energy can no longer be carried to the surface as radiation.

Instead, glowing chunks of matter, so-called granules, rise to the surface of the sun. Here they cool down and sink back into deeper layers. This process is called convection.

Brightest layer: the photosphere

The next layer is called the photosphere. It is the visible surface of the sun and, at around 6,000 degrees Celsius, comparatively cool. This zone consists of a gas layer 400 kilometers thick, which is not solid, but impenetrable.

In the photosphere, the energy from the inside is released as visible radiation to the outside, which is why it is also referred to as the brightest layer.

The solar atmosphere - two hot gas envelopes

The chromosphere and the corona together form the solar atmosphere. The chromosphere joins the photosphere as the next layer and is also called the color sphere. It was given this name because of its bright reddish color. Here the temperature rises again to around 10,000 degrees Celsius.

The chromosphere is up to 10,000 kilometers high and consists of individual gas jets. The outermost layer of the solar atmosphere is formed by the corona. This zone consists of very thin gas. You can only see the corona during a total solar eclipse.

Then it appears as a white, glowing wreath of light around the darkened sun. The temperature in this layer rises again to several million degrees Celsius.