About 4.5 billion years ago, a massive spinning cloud of gas and dust known as a “solar nebula” gave birth to our solar system. The nebula’s gravity was so heavy it collapsed. Everything swirled together to form our sun, the nearest star to Earth.
The Sun is an immense red-hot ball of gases (91% hydrogen and 8.9% helium) whose gravity pulls our solar system together. These gases get so hot they “ionize,” meaning they gain an electrical charge, and form a vast ocean of plasma on the sun’s surface, or what scientists call the “photosphere.” The constant flow of plasma on the photosphere generates the light that illuminates Earth.
At 432,168 miles in radius, the Sun is the largest object in our solar system. In fact, it makes up 99.8% of the solar system’s mass. It would take about 1.3 million planet Earths’ to fill the Sun’s mass!
Despite its colossal size, the sun is what astrologists call a yellow “dwarf star,” and it’s far from unique. Throughout the universe, there are trillions of suns, and many of them are much bigger than ours. In fact, every tiny star you see in the night sky is a giant sun in a faraway galaxy.
The Sun’s mass is held in place by what’s called “gravitational attraction,” which creates enormous pressure and temperature at its core. At 27 million degrees Fahrenheit, the Sun’s core is incredibly hot, and is where nuclear fusion takes place. During nuclear fusion, light photons are produced in a process known as “proton-proton fusion.” Light photons have an incredible journey — they take up to a million years to reach the photosphere. From there, light is dispersed into space through electromagnetic radiation, a form of energy, and reaches Earth in only a matter of minutes.
The Sun is Earth’s fuel. Without it, there would be no seasons, vegetation, weather, ocean currents, or climate. In fact, life on Earth would simply be impossible without our sun.
The study of the Sun is called “helioseismology.” Scientists study the Sun so they can understand how it affects Earth. They also study it to better understand the universe and how suns in distant galaxies may be influencing other worlds.
What is Solar Week?
NASA’s Solar Week, a week of games, online lessons, and interactive activities about the Sun for grades 5-9, which happens twice a year, took place on 12-18 October, but it’s not too late to celebrate. Check out these free activities and educational resources to learn more about the sun and the people who study it.
Also check out the IEEE TryEngineering lesson plan Solar Power! With this lesson, students complete through hands-on challenges with mini solar cells. Download it today.