The Sun
The Sun is our nearest star. Nuclear reactions deep within the Sun create the energy that makes it shine and thus the light and heat that we need for our survival. To generate this energy, the Sun consumes four million tonnes of hydrogen fuel every second, and has done so since it was born, around 4.6 billion years ago. Nevertheless, it is so large that it is expected to shine for another five billion years. However, by that time, it will have swollen into a red giant, causing Earth’s oceans to boil away and destroying all life on our planet. It may even have expanded so much that it engulfs Earth.
As well as this virtually constant outpouring, the Sun also generates energy from magnetic activity. Varying over an 11-year period, the activity can be roughly tracked by the number of dark blemishes that appear on the Sun’s surface. Magnetic explosions called solar flares often accompany these sunspots. The most recent peak in the Sun’s cycle of activity occurred in mid-2000 with a second peak at the end of 2001.
Scientists are using data from two missions in ESA's Solar-Terrestrial Programme, SOHO and Cluster, to tell them more about how the Sun works and how it affects Earth. While SOHO studies explosions on the Sun and detects solar storms heading our way, Cluster measures the effects of this activity on near-Earth space as the incoming energetic particles subject the magnetosphere to a buffeting.
Facts about the Sun
| Distance From Earth | 149 600 000 km |
| Diameter | 1 392 000 km (= 109 Earth diameters) |
| Rotation Period at Equator | 24.6 days |
| Surface Temperature | 5500 °C |
| Core Temperature | 15 million °C |
| Mass (Earth = 1) | 15 million °C |
| Volume (Earth = 1) | 1 300 000 |
| Surface gravity (Earth = 1) | 27.94 |
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