The sun, our nearest star, sustains life on Earth by producing light, rain, wind and chemical energy found in fossil fuels, and allowing plants to grow. It is the largest object in the solar system, containing 98 percent of the total mass. The temperature at the sun's core is 27 million degrees Fahrenheit and 11,000 degrees on the surface.
The sun is a giant ball of hydrogen and helium gases. Hydrogen makes up 92 percent of the sun. Helium makes up about 7.8 percent, while other trace elements make up about 0.01 percent. These trace elements include oxygen, carbon, nitrogen, magnesium and iron. Hydrogen is the simplest element, because each atom of hydrogen has only one proton. It is the most plentiful gas in the universe. Helium was discovered on the sun in 1868 by the astronomer Joseph Lockyer. The other trace elements are believed to have formed as a result of other stars found in the galaxy millions of years ago. Stars also produce energy by converting hydrogen to helium at its core. When the hydrogen supply is used up, stars will look for other ways to produce energy. They do this by attracting other elements and converting them into helium. The star can then explode into a supernova. These new elements are spread into space, contaminating the new generation of stars, like the sun.
According to evidence found from meteorites, the sun was formed at the same time as the solar system 4.56 billion years ago by gases. It started as a huge, rotating hydrogen, helium and dust molecular cloud. Due to its gravity, the ball began to compress, and as it compressed, it started to spin faster and faster. This spinning eventually flattened the ball into a disk shape, with the majority of the mass at the center, creating a gas sphere. This gas sphere attracted other materials. The added materials promoted more compression, which increased the temperature and pressure, in turn causing the atoms to fuse in the center, and the sun was born. Scientists estimate that the sun will shine for another 3 billion to 5 billion years. This number is estimated by calculating the rate at which hydrogen in the core has converted to helium. Currently, the sun has used up 37 percent of its hydrogen supply since its birth.
Hydrogen and helium work together to give off energy and light from the sun. The process is called nuclear fusion. Gravitational pressure compresses and creates extreme heat at the sun's core. Hydrogen atoms cannot survive at this temperature, so the atoms split into protons and electrons. Four hydrogen protons will then fuse with one helium nucleus causing a disproportionate mass. The excess mass is released as energy. Fifty percent of this energy is released as infrared or heat energy and 40 percent is released as visible sun light.