The sun is a star. It is a yellow dwarf, which is a medium-size kind of star. Many stars in the Milky Way are like our sun. The sun is a huge ball of gas, mostly hydrogen and helium. It is about 100 times wider than Earth. It would take 1.3 million Earths to fill it.

Let's go inside the sun. Deep in the sun's core, a thing called nuclear fusion turns hydrogen into helium. This is what makes the sun's energy. The core is the middle of the sun, and it is very hot. It is about 27 million degrees Fahrenheit.

You could not stand on the sun. It is not a solid ball. The part we call its surface is the photosphere. It is about 10,000 degrees Fahrenheit. Sunspots are dark spots on the sun. They are cooler than the places around them.

The sun is about 93 million miles from Earth, or 150 million kilometers. That is very far. Light from the sun takes about 8 minutes to reach us. Light is not all the sun sends us. Besides light, the sun gives off heat.

Never look at the sun without special eye protection. It must be made for looking at the sun. The sun's light and heat warm Earth and make life possible. Nothing could live on the sun. But its energy is vital for most life on Earth.

Words to know

• core: the middle
• photosphere: the sun's surface
• sunspots: cooler dark spots
• fusion: hydrogen into helium