The Sun
The Sun is our nearest star. Nuclear reactions deep within create energy in the form of the light and heat that we need to survive. 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.
But the Sun is so large that it is expected to shine for another five billion years. By that time, it will have swollen into a red giant, boiling away Earth’s oceans and destroying all life on our planet. It may even have expanded so much that it engulfs Earth.
Meet the Sun
| Distance from Earth | 149 600 000 km |
| Diameter | 1 392 684 km (= 109 Earth diameters) |
| Rotation period at the equator | 24.6 days |
| Surface temperature | 5500°C |
| Core temperature | 15 million°C |
| Mass (Earth = 1) | 333 060 |
| Volume (Earth = 1) | 1 300 000 |
| Surface gravity (Earth = 1) | 27.94 |
Magnetic activity
The Sun also generates energy from magnetic activity. Varying on an 11-year cycle, this activity can be roughly tracked by the number of dark spots 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 2014, with the next expected in 2025.
ESA missions
Scientists are using data from three ESA missions – Solar Orbiter, SOHO and Cluster – to discover more about how the Sun works and how it affects Earth. Whilst Solar Orbiter takes the closest ever images of the Sun to unravel the mysteries of the solar cycle, SOHO studies explosions on the Sun and detects solar storms heading our way, and Cluster measures the effects of this activity on Earth’s magnetic environment.
