The Sun
Our star, a yellow dwarf
The star the Solar System turns around: a ball of hydrogen and helium 109 times Earth's width, holding 99.8 % of all the mass the system contains. In its core, at about 15 million °C, hydrogen fuses into helium, and the energy that releases takes many thousands of years to work its way out to the surface.
What you see here is that surface, the photosphere, at about 5,500 °C, grained with cells of hot gas that rise, cool and sink back within minutes. The Sun is about 4.6 billion years old, roughly halfway through its life.
Key figures
- Diameter
- 1,391,400 km, 109 × Earth
- Mass
- 333,000 × Earth
- Share of the Solar System's mass
- 99.8%
- Surface temperature
- about 5,500 °C
- Core temperature
- about 15 million °C
- Rotation
- 25 days at the equator, 34 at the poles
- Age
- 4.6 billion years