1. The Sun: Our Star

At the heart of everything is the Sun. It is not a special object that's different from the points of light you see at night — the Sun is a star, just much closer than the rest. It is a giant ball of hot gas (mostly hydrogen), and it holds about 99% of all the mass in the solar system. That enormous mass gives it the gravity that keeps every planet in orbit.

Where does the Sun's energy come from? Not from burning like a fire. Deep in its core, under crushing pressure and heat, nuclear fusion squeezes hydrogen atoms together to form helium, releasing tremendous energy. That energy works its way out and leaves the surface (about 5,500°C) as the light and heat we receive.

The Sun even has 'weather': cooler, darker patches called sunspots, and a constant stream of particles called the solar wind that flows out across the solar system.

⚠️ Common misconception: the Sun is not a planet, and it does not burn like a campfire. It is a star that makes energy by nuclear fusion — joining atoms together, not chemical burning.

💡 Tip: the Sun = a star + fusion (hydrogen → helium) + 99% of the mass → its gravity rules the solar system.