Billions of years ago, big clouds of gas started clumping together. Gravity made them do it.
As the clump grew, so did its gravity. The stronger the gravity got, the more gas the clump pulled in. The gas packed tighter and tighter, and it heated up. Soon, the heat and pressure got too strong. In a big blast, a star was born. It was our star—the Sun—and right away, it began making energy. Billions of years later, the Sun is now middle-aged. It still pours out energy. It has used up more than half of its fuel, which is the hydrogen at its center. But don’t worry. Our Sun won’t run out of fuel for billions of years. Until then, the nuclear plant in the sky will give us heat, light, and other energy. That energy is what keeps everything on planet Earth alive.
