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Billions of years ago, huge clouds of gas began clumping together, pushed into each other by gravity.
As the clump grew, so did its gravity. The greater the gravity, the more gas the clump attracted. The gas packed together tighter and tighter, and so it heated up. Soon, the heat and pressure became too powerful. In a big blast, a star was born. It was our star—the Sun—and right away, it began creating energy. Billions of years later, the Sun is now middle-aged. It still churns out energy, but it has used up more than half of its fuel, which is the hydrogen at its core. 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.
Core
The superhot core is where atomic blasts take place. Hydrogen turns into helium, and energy is created. The energy is in the form of gamma rays, which are deadly to humans. The gamma rays begin to rise to the Sun’s surface.
Temperature: 27,000,000°F
Solar flares are sudden blasts of burning gas. They shoot millions of miles into space and release a powerful burst of energy. Solar flares and sunspots often happen together.
Radiative zone
In the radiative zone, gamma rays bounce around like pinballs. Many change into less harmful forms of energy. The Sun is so dense (thick) that energy takes millions of years to get to the surface! The energy you feel right now was created when Homo erectus—early humans—lived on Earth.
Temperature: 4,500,000°F
Photosphere
The photosphere is the visible “surface” of the Sun. Hot gases rise and carry energy up to the surface, where the energy escapes and spreads into space.
Temperature: 10,000°F
Chromosphere
The chromosphere is a layer of gas above the photosphere. It’s a part of the Sun’s atmosphere. During a solar eclipse, the bright photosphere is blacked out, and that’s the only time we are able to see the chromosphere.
Temperature: 50,000°F
Corona
The corona, or “crown,” is the Sun’s upper atmosphere. Like the chromosphere, it is visible only when a solar eclipse is in progress.
Temperature: 4,000,000°F
“If there exists a cosmic ballet, it is among the solar system’s planets as they wander against the background stars with orbits and paths that are choreographed by the forces of gravity.”
—Neil de Grasse Tyson, Universe Down to Earth
▲ This is a picture of a solar eclipse, taken in 1905 at the Munich observatory. A solar eclipse is caused by the Moon getting between the Sun and the Earth.
▲ A star’s color tells us how hot or cold it is. Blue stars are the hottest and brightest, while stars of medium heat are yellow. The coldest and dimmest stars are red. Our Sun is classified as a yellow dwarf, even though it’s in the middle range for size.
Sunspots are dark blotches on the surface of the Sun. They build up in a cycle and reach their peak numbers about every 11 years. The spots are cooler than the rest of the Sun’s surface, if you can call 7,800°F cool! ▼
▲ Why do solar flares happen?
Flares occur when energy that has built up in the Sun’s atmosphere is suddenly released. The area erupts in a violent explosion.
What happens when the energy of a solar flare reaches Earth?
▲ Astronauts have to come back to Earth or take cover for protection, because the radiation is deadly. (Earth’s atmosphere shields people on the ground.)
▲ Extreme flares can knock satellites out of their orbits. They can also mess up communications systems on Earth.
▲ During a solar flare, the northern and southern lights become even more stunning. Particles that come from the solar flare help to create the bright colors.
Check It Out!
What would the Sun look like if you were on Mercury, the planet closest to it?
It would look nine times bigger than it does to us on Earth. It would also look a little bigger and then a little smaller. That’s because Mercury’s orbit is an oval, or ellipse.
