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What Happens as You Get Toward the Center of the Sun?

For thousands of years, humans have looked up at the sky and wondered what that great, life-giving ball of light was. Many early civilizations believed the sun was a god. As civilizations became more scientifically advanced, our understanding became clearer. Now, astronomers know quite a lot about the sun, including what it is made from and how it works.

The Chromosphere
- The outside layer of the sun is called the chromosphere. It is nearly 2,000 km (1,250 mi) thick and can reach temperatures as high as 20,000 degrees Kelvin (35,000 F). The chromosphere is nearly invisible to humans, thanks to the incredibly bright photosphere below it, but it is possible to see it during a solar eclipse or with special instruments. The chromosphere is covered by magnetic field lines, which hold everything together.
The Photosphere
- The second layer of the sun is called the photosphere. It is the part of the sun that produces most of the light we see. It is 500 km (310 mi) thick, which seems huge but is actually thinner than an onion skin in comparison to the rest of the sun. Temperatures in the photosphere can reach between 4,500 and 7,500 K (7,500 to 13,000 F). As of 2011, scientists are unsure why the photosphere is cooler than the chromosphere.
Convective Envelope
- Below the photosphere lies the sun's convective envelope. This is the section of the sun that energy from the core has to travel through before it is released as light and heat. Hot matter from the core rises through the area, until it reaches the top and cools, forcing it to drop back toward the core. The process repeats over and over, so that the whole area moves like a pot of boiling water. The upper part of the convective envelope are 660,000 K (1,200,000 F) while the lower part can reach temperatures over 2,000,000 K (3,600,000 F).
Radiation Zone
- The radiation zone is the area surrounding the sun's core. This dense section of the star slowly transfers energy away from the center, cooling it as it goes. Energy is transferred from one atom to the next, and it takes 170,000 years for energy to travel through this region because it is transferred between atoms randomly rather than taking a direct route out.
The Core
- The core of the sun is an incredibly dense and hot factory that destroys atoms to create the energy that provides us with light and heat. Temperatures at the core reach an astounding 15,000,000 K (27,000,000 F), and nothing known to man can survive there. The density of the sun's core provides most of its mass, making its gravity so strong it is able to keep Earth (and the rest of the solar system) in orbit.

Astronomy