card
047

Sun

OLogy Series
place
card
047

Sun

OLogy Series
place

Ninety-three million miles from Earth, a giant ball of hot gas brightens the sky. Nuclear reactions in the Sun's core create energy, which gradually flows to the Sun's surface. This energy reaches Earth in the form of sunlight. The Sun's heat and light warm Earth's surface, drive weather and currents, and make life possible on our planet. We experience the Sun's energy every time we feel its warmth on our skin or see with the aid of sunlight.

A Burning Question
Life on Earth is dependent on the energy from the Sun. All of our food needs sunlight to grow. Where does the Sun get so much energy? Scientists have been trying to figure this out for hundreds of years. Some believed that the Sun was a colossal lump of burning coal, but then where was all the smoke? Others thought it might be covered with volcanoes -- that would be a lot of lava! Another explanation was that its surface was heated by endless meteorite showers. Only over the last 150 years have we begun to understand how the Sun and other stars really work. The Sun's tremendous energy is produced when atoms of hydrogen are fused together. The Sun produces more energy every second than has ever been used by all people on Earth!

How long has the Sun been shining?

460,000 years

4.6 million years

4.6 billion years

Are you right?

Correct!

Our Sun is a middle-aged yellow star that is nearly halfway through its lifespan. It formed in a cloud of gas and dust about 4.6 billion years ago. It will run out of fuel in about 5 billion years.

About how long does the Sun's light take to reach Earth?

8 seconds

8 minutes

8 hours

Are you right?

Correct!

Sunlight reaches us about 8 minutes after it leaves the Sun. In that time it travels 93 million miles at the speed of light.

Neil Tyson, astrophysicist

Our Sun is an ordinary star, like billions of others in the Milky Way.

The surface of the Sun never changes.

Fact
or
Fiction
?

Fiction

The surface of the Sun is always changing. Flares, sunspots, and "starquakes" keep the Sun's surface in constant motion.

A million-mile-per-hour wind blasts out from the Sun across the entire Solar System.

Fact
or
Fiction
?

Fact

This powerful wind of hot gas flows out from the Sun's extremely hot outer layers. Fortunately, Earth's magnetic field and atmosphere protect it from this solar wind.

The Sun makes up about 98.6 percent of the Solar System's entire mass.

Fact
or
Fiction
?

Fact

If you combined all the planets, moons, asteroids, comets, gas, and dust that orbit the Sun, they would make up only 1.4 percent of the Solar System's mass.

Age: 4.6 billion yrs. old Diameter: 870,000 miles
Average Core Temp.: 27,000,000 degrees F
Average Distance from Earth: 93,000,000 miles
Characteristics: middle-aged yellow star; more massive than the average star; produces energy in its core when hydrogen & helium fuse together
Significance: produces heat and light required for life on Earth; drives weather and climate
Cool Fact: The Sun's gravity holds our Solar System together!

Image credits: courtesy of NASA; Neil Tyson: AMNH.