The star that serves as our sun is nearly 4.6 billion years old and consists of extremely hot plasma. The sun’s mass is more than every planet in our solar system put together and can generates enormous amounts of energy through nuclear reactions.
The Sun’s Atmosphere
The atmosphere above the sun’s surface consists of three layers, the photosphere, the Chromospheres and the Corona. The photosphere is the lowest region of the atmosphere and can be seen from earth. The average temperature of this region is about 5,800 degrees Kelvin. The outer edges of the photosphere cool down significantly and appear dark, giving the sun its defined looking edge. Above the photosphere is the chromosphere within which the temperature varies between 4,500 degree Kelvin and 10,000 degrees Kelvin. This layer of the atmosphere has many flame-like columns of plasma that are termed spicules which can rise up 6,000 miles from the sun’s surface. The last layer of the atmosphere is the corona. This layer consists of thin plasma is very hot, reaching 2 million degrees Kelvin. Scientists are currently studying the reason why the corona is so hot. The current theory is that it is somehow related to the sun magnetism.
The Sun’s Surface
The surface is a layer of plasma which is approximately 60 miles thick. The surface is covered in bumps which bring up hot plasma from inside the sun. The surface of the sun is also covered in sunspots. These spots are cooler regions that look dark against the rest of the extremely hot surface. There are also intensely bright spots that are also associated with the sun spots. Sunspots are the result of a concentration of the sun’s magnetic field, which stops the flow of heat from inside the sun.
The Sun’s Internal Structure
Inside the sun there are three layers with a core at the center. In the core of the sun there are extremely high temperatures and very high amounts of pressure. This spot within the sun is the area where nuclear fusion occurs. After the core comes the radiative zone, which is the zone that energy from the core travels through. It takes nearly 1 million years for the energy to travel out in the form of photons. The last zone inside the sun is the convection zone. The energy that eventually makes it through the radiative zone, concentrates in the convective zone. From there is enters the photosphere and from there is released as light and heat.
Source: Rees, Martin. Universe: The Definitive Visual Guide. DK Publishing, New York. 2008.