They are thought to be caused by interactions with particularly strong regions of the underlying magnetic field, which slightly reduce the radiation coming up from the core, cooling the surface. These cooler spots can be up to 50,000 kilometres across. The temporary splodges across the surface appear darker to us than the warmer plasma surrounding it. Sunspots are cooler parts of the Sun's surface, and occur in the photosphere. The equatorial regions take just 24 days to rotate and the polar regions more than 30. On average, it takes 27 Earth days for the Sun to rotate once on its axis, but different parts move at different speeds. Even though the Sun is not solid like Earth, it still has a rotation as the plasma swirls around its surface. The most abundant of these include oxygen, carbon, nitrogen, silicon, magnesium, neon, iron, and sulphur. In addition to hydrogen and helium, scientists have detected at least 65 other elements in the Sun. This is called solar wind - under certain conditions, when it hits Earth's atmosphere it can cause auroras, such as the Northern Lights. When the plasma is heated to the temperatures seen on the Sun, it contains so much energy that the charged particles can escape the star's gravity and blow out into space. Under intense heat and gravitational force this is fused into helium during nuclear fusion. The Sun is a ball of gas and plasma - around 91% of it is hydrogen gas. This dramatic increase in temperature in the atmosphere is one of the star's biggest mysteries. As distance from the core of the Sun grows wider, the temperature would be expected to drop. In the Sun's atmosphere, known as the corona, the temperature begins to rise again to roughly two million degrees Celsius. By the time it gets to the surface the temperature is down to a much cooler 5,973☌ - but it's still hot enough to boil diamonds. At this point the temperature drops to around two million degrees Celsius. The energy produced at the core takes up to a million years to reach the outer layer known as the convective zone. This releases an extraordinary amount of energy which in turn is released as heat and light. This is hot enough to sustain thermonuclear fusion, when hydrogen atoms are fused together to form larger helium atoms. The core is the hottest part of the Sun, at 15 million degrees Celsius. Due to its huge mass and strong gravity, the Sun is a near perfect sphere. Some stars are just a tenth of its size, while others are more than 700 times bigger. It contains 99.86% of the mass of the entire solar system and could contain roughly 1.3 million Earths. The Sun is the biggest object in our solar system, with a distance of 695,508 kilometres from centre to surface.

The sun origin guide