The Sun

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The Sun's Layers

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The core, or very center, of the sun is the main region where nuclear reactions take in hydrogen to form helium, creating energy. The temperature is approximately 15,000,000 degrees Celsius and the density is about 150 g/cm cubed.

Radiative Zone

The layer stretches from the edge of the core to the base of the convective zone. In it, energy from the core is transported in the form of radiation. Photons bounce from particle to particle while in the radiative zone. The density drops from 20 g/cm cubed to 0.2 g/cm cubed across the radiative zone, and the temperature goes from 7,000,000 degrees Celsius to 2,000,000 degrees Celsius.

Convective Zone

This is the outermost layer of the interior, and is found from a depth of 200,000 km to the visible surface. At the base of this zone temperatures average about 2,000,000 degrees Celsius. Although this is certainly hot, it's cool enough for heavier ions like carbon, nitrogen, oxygen, and iron to hold onto most of their electrons, causing this layer to be opaque and more difficult for radiation to pass through. This trapping of heat makes the fluid unstable, so it convection is created. The density is 0.0000002 gm/cm cubed.


This layer is the visible surface of the sun. It is about 100 km thick. Often, things like sunspots, faculae, and granules can be seen on the photosphere using a good telescope. The temperature ranges from 4,230 degrees Celsius to 5,730 degrees Celsius, and the density is 10^(-9) g/cm cubed.


The chromosphere is an irregular layer that lies above the photosphere. In it, the temperature rises to 20,000 degrees Celsius. These rising temperatures make the hydrogen give off a reddish colored light. Features like a chromospheric network of magnetic fields, plage around sunspots, dark filaments, and prominences are found on this layer. Its density is 10^(-12) g/cm cubed.


This is the sun's outer atmosphere. It can only be viewed during total eclipses, and often changes from eclipse to eclipse. The shape of the corona changes in time with the sunspot cycle. It is 800,000 to 3,000,000 degrees Celsius, and this high temperature causes x-ray emissions. The density is 10^(-16) g/cm cubed.


These look like dark spots on the sun's surface. They will usually last for several days, but large ones can stay for weeks. They are magnetic regions with an extremely strong magnetic field. Sunspots will most likely come in groups of two, in which one will have a positive magnetic field and one will have a negative. The darkest areas of the sunspot are the parts with the strongest magnetic field.


These are dense clouds of material hovering above the surface of the Sun (loops of magnetic field hold them in place). Often, they stay quiet and undisturbed for days or weeks, until the magnetic loop that holds them up begins to change. Then, they rise up and erupt in a matter of minutes of hours.

Solar Flare

A solar flare is an explosion on the surface of the sun. Within minutes, they can heat material to millions of degrees a create as much energy as a billion megatons of TNT could. They usually occur near sunspots. These flares release energy in the form of electro-magnetic energy, energetic particles, and mass flows.


Also known as the Northern and Southern Lights, auroras are due to solar winds (caused by CMEs). When this solar wind reaches Earth, the solar particles and magnetic fields cause the release of particles trapped near Earth, triggering reactions in the upper atmosphere, where nitrogen and oxygen molecules release photons of light.