What is a Radiation Zone?

Instructor: Danielle Reid


Did you know that inside of the Sun there are different layers where energy can travel? Explore this lesson to learn about one of those layers called the radiation zone. Discover what a radiation zone is and its role inside the Sun.

Introduction: The Many Layers of The Sun

The Sun, in all of its glory, is one beautiful star. Let's imagine we are an energy particle, called a photon, zipping around inside of the Sun. If we crack open the Sun and see its 'insides,' as shown in the diagram, you will notice a series of layers. We have the core, radiation zone, and convection zone. As a photon we first must originate from the Sun's core. At the core, this is the electrical heartbeat for the Sun. In other words, this is the site where reactions are taking place firing off energy that will eventually leave and produce sunlight. Of course we must mention the temperature for each of these layers. At the core, as you might suspect, it is very hot! 15 million degrees Celsius to be chemically correct.

Diagram Showcasing the Layers of the Sun

Zooming around as a photon, we must head straight entering the front door of the next layer called the radiation zone. The radiation zone is the site where energy transport occurs. This zone can be characterized as the place where we, the photons, bounce around facilitating the ability for energy to be transported to the outer surface of the Sun. The temperature at the radiation zone ranges from 2 to 7 million degrees Celsius.

Continuing on with our journey, as a photon, our last stop must be the convection zone. At the convection zone this is the outermost layer of the Sun where convection currents occur. The convection currents take us, the photon, to our final destination: which is the outer surface of the Sun. The temperature of this zone is approximately 2 million degrees Celsius.

Radiation Zone: Overview

Recall that the radiation zone is the site where energy transport occurs. This energy is carried by photons. Extending outside of the Sun's core, the radiation zone occupies roughly 45% of the Sun's radius. An illustration of this is shown below. So how does the radiation zone play such a pivotal role in making sure energy, produced from the Sun's core, travels to the outer surface? Great question!

The Radius of the Sun in Relation to the Radiation Zone

There are different methods that can be used to physically transport energy to the Sun's outer surface. However, one efficient way is through the use of radiation. Gamma radiation is the type of radiation used. The following diagram illustrates what happens to a photon as it travels through the radiation zone.

What Happens When a Photon Travels to the Radiation Zone

When a photon enters this zone it travels a small distance before it is absorbed by a particle. Once it is absorbed, it is spitted out or re-emitted causing it to change its direction in a random way. The photon then travels another small distance before being absorbed again by a particle. Once absorbed it is spit out or re-emitted and changes direction, yet again, in a random way. This process of traveling a small distance, being absorbed, re-emitted, and travelling in a random direction continues until the photon reaches the Sun's outer surface.

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