Throughout history, people have believed that solar energy comes from fire. They believed this because if their fire produces heat and energy, so does the sun, right? The energy of the sun, they understood less than 100 years ago, comes from the mass on the surface resulting from nuclear fusion! Nuclear fusion occurs in the nuclei of hydrogen atoms to form a more massive nucleus, which releases an enormous amount of energy. Nuclear fusion that occurs in the sun is the collision and/or fusion of two hydrogen nuclei. First, a proton's positive charge is neutralized and emits a particle called a positron, transforming the proton into a neutron and transforming the original protons into a proton-neutron pair. Second, another proton combines with this proton-neutron pair to produce a nucleus composed of two protons and one neutron. Third, two nuclei composed of two protons and neutrons collide and/or merge. As fusion proceeds, two protons are released. The remaining two protons and neutrons are merged to form a helium nucleus. At each stage, energy is released. The energy released during the three stages of nuclear fusion is what makes the sun bright and gives it a very high temperature. The scientist cannot see the interior of the sun, but computer models have revealed what the invisible layers may look like. In the center of the sun is the wound. The core represents 25% of the total diameter of the Sun, or 1,390,000 km. the temperature of the sun's core is about 15,000,000 degrees Celsius. No liquids or solids can exist in the core due to the incredibly high temperatures. The core, like the entire sun, is made of ionized gas. The mass of the Sun is 300,000 times that of the Earth. Due to the large mass of the sun, the pressure exerted by the sun... middle of paper ...... is exerted on these areas. In some places the magnetic field is 10 times stronger than in other places, because less energy is transferred, these regions of the photosphere are up to 3.00 Celsius colder than the surrounding regions. Although they still shine brightly, these cooler areas of the sun appear darker than the areas around them. A large sunspot has a diameter of more than 100,000 km, several times the diameter of the Earth. The sunspot cycle lasts about 11 years. A sunspot cycle begins when the number of sunspots is very low but begins to increase. Sunspots initially appear in groups halfway between the equator and the sun's poles. The number of sunspots increases over the years until it reaches its maximum of 100 or more sunspots, then begins to decrease to its minimum just to start its 11-year cycle again..