Earth’s Place in the Universe

The Sun

Thank goodness for the sun! Life couldn’t exist on Earth without it. There are lots of reasons why. For one thing, the sun’s heat keeps Earth from being an unlivable ball of ice.

What exactly is the sun? What are some of the ways our world depends on it? And how does it sustain life?

Bringing life to planet earth

Star of the Show

Our solar system just has one sun. Some solar systems have two or more! But one sun is all we need.

Not only is our sun the star of the show here on Earth, it’s actually a real star. Although our sun may be special to us, it’s just one of millions and millions of stars in the universe. Just look up at the sky on a clear, dark night and you will see plenty. Stars come in different types. Ours is a type called a yellow dwarf star. Even though it’s closest star to Earth, it’s still 94.43 million miles away from us.

Our sun formed from space dust 4.6 billion years ago. That same cosmic dust formed all the planets in our solar system, including Earth, but most of it went into making the sun. In fact, the sun contains more than 99% of all the matter in our solar system. Even though it’s not the biggest type of star, our sun is big enough to fit more than one million planets the size of earth inside it.

The sun is made almost completely of just two elements: hydrogen and helium. It is very hot: over 10,000° Fahrenheit. That heat is generated by a reaction between hydrogen and helium called a fusion reaction. That is far too hot for an astronaut, or even a spaceship, to get close to. No wonder NASA isn’t planning any missions to the sun anytime soon.

The closest star

Bringing life to Earth

The sun’s heat is the only reason we exist here on Earth. It warms our planet to just the right temperature for life.

The sun gives us more than warmth. Plants—the basis of all our food —need the sun’s energy to create their own food. Without the sun, we wouldn’t have flowers, apples, broccoli, wheat, sugar, or any other food. Plants are more than food: without them, our atmosphere also wouldn’t have the oxygen that we need to breathe. Besides food and warmth, our bodies need sunlight, too. It provides us with Vitamin D, an essential ingredient for healthy bodies.

So, the next time you are enjoying a meal, savoring a warm afternoon, or just feeling grateful for the life all around you, don’t forget to thank your lucky star: our sun.

Written by Laura McCamy

Edited by Beth Geiger, MS Geology

Illustrated by Renee Barthelemy