The Sun, Our Star

The Sun is the star at the very centre of our solar system. It is an enormous ball of hot glowing gas — mostly hydrogen and helium — that has been shining for about 4.6 billion years. Everything in our solar system, from tiny Mercury to distant Neptune, travels around the Sun, held in place by its powerful gravity.

Deep in its core the Sun squashes hydrogen atoms together in a process called nuclear fusion. This releases enormous amounts of energy that travel outwards as light and heat. Without the Sun there would be no warmth, no weather, and no life on Earth. In fact, almost all the energy living things use can be traced back to the Sun.

Here is a surprising idea: the Sun is not actually on fire like a bonfire. A fire needs oxygen to burn, and space has no oxygen. The Sun's heat comes from fusion, not from burning. It is a completely different and far more powerful way of making energy.

The Sun has an outer atmosphere called the corona. It is much hotter than the visible surface, reaching millions of degrees. During a total solar eclipse, when the Moon blocks the Sun's bright face, the corona glows like a beautiful white crown around the dark circle.

The Sun is not perfectly calm. Dark, cooler patches called sunspots come and go on its surface, and it sometimes flings out giant bursts of particles called solar flares. These bursts travel across space and, when they reach Earth, can create the beautiful glowing lights near the poles called auroras.