The Sun is the star at the center of our solar system. It is mostly hydrogen - about three quarters of its total mass - and helium - about one quarter of its total mass. The remainder of its mass is other elements found in much smaller quantity adding up to just under two percent of the sun's mass. These elements include carbon, nitrogen, oxygen, neon, magnesium, silicon, sulfur, and iron. Over 50 other elements are found in trace amounts. The temperature of the Sun's surface is 5778 K (5505°C).
The energy from the Sun is vital to life on Earth. Not only does it allow life to exist, but it also is the source of most energy humans use. Biomass, fossil fuels, and some renewable energies such as wind and solar power originate from the Sun. Fossil fuels are simply solar energy stored in a secondary form. The original energy from the Sun is captured through photosynthesis and stored in chemical bonds as plants grow. This energy is then released millions of years later after these plants have transformed into fossil fuels. All fossil fuels are ultimately energy from sunlight. The solar energy to the Earth is significant, even after passing through hundreds of kilometers of the Earth's atmosphere. The solar radiation that reaches the Earth has a significant amount of energy. At full intensity, the solar power to the Earth at the surface of the upper atmosphere is about 1367 W/m2. Taking into account the fact that only half of the Earth faces the Sun, as well as accounting for the different amounts of sunlight that hit different latitudes and the amount of atmosphere the sunlight has to pass through, the average power amounts to around 340 W/m2.
In addition to providing energy, the Sun's energy warms the Earth to a point that it is habitable (the structure of the atmosphere also helps to ensure that the Earth's energy budget maintains a constant, livable temperature). The Sun also creates weather patterns, ocean currents, and air currents.
Satellites have been launched to study the Sun continually. These satellites observe the Sun in a variety of wavelengths that helps to create a picture that describes the inner workings of the Sun. The Sun is believed to be made up of 6 different regions:
Figure 2. This is a three dimensional model of the Sun provided by NASA. Drag the image around to look at the Sun from different angles.
For more information on the energy that comes from the Sun, see:
For more information on how this energy is important on Earth, see: