The surface of the sun is both a barrier and an indicator of the inner workings of the sun. The surface of the sun is a constantly shifting dynamo of fiery gas. When the sun's surface is moving, it is hard to see into the inside of the sun. However, scientists can extrapolate the activity inside the sun based on what happens on the outside of the sun. Changing mass and pressure inside the sun causes vibrations which can be tracked from the outside of the sun.
Inside the sun are layers and in each layer a different chemical process occurs. The center of the sun is also called the core. This is where the sun produces the energy that lights up our planet and provides us with warmth. The core is extremely hot. Under these conditions, nuclei that would normally repel each other fuse together instead. In the core, hydrogen joins together to make a helium nucleus. This releases positrons and neutrinos and radiation energy called gamma-ray photons. The fusion in the Sun's core also creates 99 percent of the Sun's heat or thermal energy. The rest of the sun becomes warm when the heat created by fusion moves outward from the core through the layers outside.
Streams of photons move into the radiative zone, which reaches 70 percent of the way to the Sun's surface. In the radiative zone, the photons move slowly, taking tens of thousands of years to cross into the convection zone. In the convection zone, moving gases bubble and mix and move up to the surface of the Sun. The surface is also called the photosphere. Most of the light that we see comes from the lowest part of the photosphere. The sun makes light that we can see because the fusion in its core creates intense thermal energy that is superheated. We see this very hot thermal radiation as light. The Sun also makes somewhat cooler thermal radiation that falls into the infrared part of the electromagnetic spectrum. This light is not visible to the human eye.
In 2009 NASA launched the Solar Dynamic Observatory, a machine that is specifically designed to look inside the sun. The observatory will not travel all the way into the center of the sun, but it will capture an image from the outside. The process is similar to the way an ultrasound works.