You Light Up Our Life
We owe a lot to the round glowing object known as the Sun. It makes our days bright and warm. It’s the energy source that lets plants make food to feed us all. The Sun creates seasons, weather patterns, ocean currents, and even sleep patterns for most living things. Lucky for us on Earth, the Sun is the perfect distance, brightness and size to energize and sustain our delicate balance of life. Without the Sun, Earth would be a frozen, lifeless rock. But exactly what is the Sun?
The sun’s energy and heat help sustain life on planet Earth.©G.Ellis/GLOBIO.org
Hot Stuff
The Sun is a huge, burning ball of gas that gives off heat and light through nuclear reactions. It is also a star – the star closest to Earth. Not that it’s really close. The Sun is about 150 million km away. If you were in a car traveling 96.5 kph, it would take you about a million and a half hours to get there. That’s about 177 years!
The sun is a huge, burning, ball of hot gas in space.©NASA
It’s not the biggest star in the universe, but it is the biggest object in our solar system. It contains a whopping 99% of all the matter—the rocks, dust, gas, and other stuff -- in our “neighborhood.” If the Sun were hollowed out, a million Earths could fit inside.
The Sun’s enormous size gives it enormous gravitational pull. Its gravity works like an invisible anchor on the planets and heavenly objects that orbit around it. Without the Sun’s gravity, they would fly off into space.
The sun is a million times bigger than Earth.©NASA
A Star Is Born
Our Sun came about the same way other stars did. About 4.5 billion years ago, after the Big Bang had thrown matter out into empty space, some gas (mostly hydrogen) and dust began to spin around together in a big cloud called a nebula. The cloud spun for about 100 million years, becoming hotter and denser. Gravity made the cloud collapse into its center, forming a disk. The disk dropped out and became the Sun. The dust left behind became the planets and other heavenly objects in our solar system.
Spinning Wheel
The Sun is still spinning. It rotates on its axis approximately once every 26 days. Along with about a gazillion other stars, it orbits the center of our galaxy, the Milky Way. That’s a really long trip! It takes about 250 million years to make one revolution.
It’s a Bomb. Really.
It may look solid, but the Sun is made up of gas--mostly hydrogen and helium. Incredibly hot gas. The whole Sun is raging hot, but there are six different levels of heat and pressure. In its core, where it’s hottest, hydrogen atoms are squeezed and pressed so hard they split. Then they come back together again to make another gas, helium. This is a violent, explosive process called nuclear fusion. It’s the same way nuclear bombs are made.
Deadly rays work their way from the core to the outer layers. There they spend about a million years whipping around and bouncing off each other. This activity makes them lose energy. By the time they finally spill from the surface of the Sun and shine out to the objects in our solar system, the rays are safer.
Sun Power
Eight minutes after it shines out from the Sun’s surface, the Sun’s energy reaches Earth in the form of light and heat waves. Except for nuclear energy, all of the energy on earth comes from the Sun’s energy.
- The oil, coal, and gas that we burn are known as fossil fuels. They come from the remains of prehistoric plants and animals that originally gained their energy from the Sun.
- The electricity we use mostly gets its oomph from burning fossil fuels.
- Wind power and wave power depend on the weather patterns that are caused by the Sun’s energy.
- Solar power? Directly from the Sun’s rays.
Most of the energy used on Earth comes from the sun. Solar panels collect and convert energy from the sun into useable energy.©Roger Taylor/DOE/NREL
Have a Slice of Sunshine
Even our own power comes from the Sun, through the foods we eat. Sunlight creates sugars in plants in a process called photosynthesis. Plants use the sugars for food. Then animals, including humans, eat plants. They also eat other animals that have eaten plants.
What’s your favorite food? You can trace it back to the Sun. Take pizza. The sauce is made of tomatoes, which come from a plant. The crust is made from flour that comes from wheat, which is a plant. The cheese comes from milk, which comes from cows, which eat grass -- which is a plant!
All living things on Earth get their energy from the sun either directly or through the food they eat.©G.Ellis/GLOBIO.org
How Can Snow Come from the Sun?
Every kind of weather happens because of the Sun, too -- even rain and snow. How? Heat energy from the Sun warms Earth’s surface. That makes the water in oceans and lakes evaporate into the air. This water vapor gathers into clouds. The clouds eventually burst, bringing rain or snow.
Land warmed by the Sun heats the air above it, too. This creates winds and air currents. The Sun’s warming rays also create ocean currents, which bring weather patterns. Even stormy weather comes from sunshine.
Sun Spots and Solar Flares: Storms on the Sun
Constant storms on the sun’s surface are called Sun spots.©Greg Piepol
The Sun itself is a stormy place, with storms called Sun spots on its surface. Eruptions called solar flares send out bursts of radiation and energy thousands of miles into space. Solar flares are incredibly hot—anywhere from 2 to 13.3 million degrees C. Recently scientists have discovered that solar flares can cause Sunquakes—like earthquakes—that violently shake the Sun.
Solar Wind and a Polar Lightshow
Solar winds are the cause of beautiful light displays in called auroras. Auroras occur in the night sky at the North and South poles.©NASA)
Sun spots and solar flares produce a constant stream of particles. The stream loops off the surface of the Sun into space. This stream is called solar wind, and it can push around satellites, bend comet tails, and disrupt electronic communications on Earth. The solar wind also causes dazzling displays of color in the sky called the Northern and Southern Lights. These happen near the North and South poles. That’s because Earth’s magnetic field is weaker at the poles. More solar wind particles can enter the atmosphere there.
Lunar and Solar Eclipses
When the earth and moon’s orbits cross paths, the moon blocks the sun. This is called an eclipse.©Anthony Ayiomamitis
Earth orbits the Sun. The Moon orbits Earth. Sometimes the two get in each other’s way. When that happens, the Sun’s light is blocked. We call this an eclipse.
- A lunar eclipse happens when Earth passes between the Sun and the Moon. It casts a shadow that blocks the Sun’s light from reaching the Moon.
- A solar eclipse happens when the Moon passes between the Sun and Earth. This is much rarer. The sky slowly gets dark as the Moon moves in front of the Sun and blocks the light. When the Moon and Sun are in a perfect line, we call it a total eclipse of the Sun. Note: Never, ever look directly at a solar eclipse. It can permanently damage your eyes. Actually, you should never look directly at the sun, eclipse or no eclipse.
Going Outside? Put on Your Coat (of Sunscreen)
The Sun’s energy comes to us in waves of radiation. Many of them get filtered out through our atmosphere, but not all. Ultraviolet waves can burn our skin. Even worse, these waves can cause skin cancer. Sunscreen can filter out the harmful rays, so slather it on before you head outside.
Celebrating the Sun’s Special Events
The Mayans, like other ancient civilizations, studied astronomy and built temples to observe the sun.©M.Wilhelm/GLOBIO.org
Because it was a source of heat and light, the Sun has been worshipped by people and cultures throughout time. Prehistoric monuments such as Stonehenge in England and some of the pyramids in Mexico were built to observe specific Sun events like equinoxes. These occur twice a year, when the length of day and night are exactly the same. The Vernal Equinox happens around March 21. The Autumnal Equinox happens around September 21.
Solstices happen twice a year, too. During the summer solstice, on June 21, Earth’s axis tilts the most towards the Sun. During the winter solstice, on December 21, the axis tilts the most away from the Sun. Machu Picchu in Peru was built in the 1400s primarily as an astronomical observatory to study these events.
March, June, September, December – that’s the Sun, marking off the four seasons. Is there anything it doesn’t do for us on Earth? No.
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