The Sun: Our Own Star

The Sun is a star — an enormous ball of extremely hot, glowing gas that makes its own light and heat. It is not a planet, and it is nothing special among stars. It looks huge and blinding for one reason only: it is by far the closest star to us, about $150$ million km away, while the next-nearest star is tens of thousands of times further off.

The Sun sits at the centre of the solar system. Everything else — the eight planets, their moons, the asteroids and the comets — travels around it.

Some sense of scale: about a million Earths would fit inside the Sun, and its light takes roughly $8$ minutes to reach us. Sunlight you feel on your arm left the Sun before break started.

Why the Sun matters here on Earth. It is not just a light in the sky:

• Every producer in every food chain runs on its energy, so every meal you have ever eaten traces back to it.
• It warms the land, the sea and the air, which is what drives our weather.
• It evaporates water from the ocean, and that water eventually falls as the rain our farms depend on.
• It powers the solar farms of the Northern Cape and the panels on many South African roofs.

Worked example — planets versus stars. Why can you see Venus shining brightly in the evening if it makes no light of its own? Because it is reflecting sunlight back to you, the way a road sign flashes in a car's headlights. Stars shine with their own light; planets and moons only ever borrow the Sun's.