The Sun

Solar Activity
Sun animation
Credit:SOHO

The Sun is average star, but without its energy we would not exist.

It contains more than 99.8% of the total mass in the Solar System, with the planet Jupiter containing most of the rest. The Sun is primarily made up of hydrogen (75%) and helium (24%), together with small amounts of oxygen, carbon, neon and iron.

The Sun was born in a giant cloud of gas and dust, which collapsed under the force of its own gravity. As this material fell inwards it created a lot of heat and pressure. When the temperature in the middle, the Sun's core, reached about 1 million degrees it ignited causing it to begin nuclear fusion. When this happened, the Sun began producing its own light, heat, and energy. It takes about 50 million years for the Sun's energy to make its way from the core to the surface, and then another 8 minutes for the light to reach us here on Earth.

Astronomers have calculated that the Sun is about 4,500 million years old and should continue shining for another 5,000 million years or so before running out of fuel and undergoing a relatively peaceful death. The Sun is a very active place, as you can see from the SOHO animation (see right), and significant variations can be seen from day to day, and year to year. The activity arises from the bending and twisting of magnetic lines within the atmosphere of the Sun, which can lead to sunspots and solar flares.