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A
ground-based view of a prominence on the Sun's limb seen in H-alpha
light.
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| THE SUN | ||
| Without the Sun there would be no Solar System. The Sun does not just provide the energy required for life, but also provides the gravitational force to hold the planets in their orbits. | ||
| Orbit | ||
| The Sun orbits the centre of our galaxy at a distance of 8,500 parsecs, where a parsec is 30.86 million million kilometres. The Sun's orbital period is about 240 million years. Mapping of our galaxy has been underway for many years, and consequently we are reasonably sure of the Sun's location in the galaxy. | ||
| The Sun rotates with an average period of 27 days. However, the rotation period varies with latitude - equatorial regions have a rotational period of 25 days, whereas polar regions are slower and take 34 days to complete one rotation. | ||
 The location of the Sun in our galaxy. |
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| Physical properties and structure | ||
| The Sun is the most massive body in the Solar System, containing 98% of the mass of the Solar System. The Sun is more than 330,000 times more massive than the Earth. The Sun is also the Solar System's largest body, with a diameter of 1,391,900 kilometres, over 109 times that of Earth's. | ||
| The Sun is layered, and can effectively be divided into three regions, the core, the radiative zone, and the convective zone. The "surface" of the Sun that we see is the photosphere, above which lies the chromosphere and the outlying corona. | ||
 Comparison between the Sun and Earth. |
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| More about the Sun's structure | ||
| The dynamic surface | ||
| The surface of the Sun is exceptionally dynamic - a seething mass of convection currents, storms, flares, and huge prominences. Many of the solar surface features dwarf the Earth. | ||
 A prominence on the Sun's limb seen in H-alpha light. |
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| More about the Sun's activity | ||
| Solar wind | ||
| There is a constant outpouring of solar material - solar wind - that streams across the Solar System and reaches every planet. The interaction between the solar wind and the planet's magnetic field generates auroral displays. | ||
| More about solar wind | ||
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