NASA's Space Place
The Sun: More Than an Average Star
By Linda Hermans-Killam
National Aeronautics and Space Administration
There is one object in space that is more important to us on Earth than anything else in the universe. It is a bright star that lies at the very center of our solar system. That star is our sun. It is a huge ball of superhot gas, made up mainly of hydrogen and helium. The sun is by far the largest object in our solar system. The Earth orbits around our sun, and so do all the other planets, dwarf planets, moons, asteroids, and comets in our solar system.
The sun is really just an average star, like trillions of other stars in the universe. But to us, it looks so big and so bright! How can it be like the tiny points of light that we see in the night sky? It appears so much larger and brighter than other stars because it is much closer to us than any other star.
So how close is the sun? The sun is around 93 million miles (150 million km) from Earth. This is so far that it would take about 163 years to get to the sun if you traveled at a speed of 65 miles per hour (104 km per hour)—the speed of a car on the freeway. That might seem incredibly far away. However, the next closest star to us is about 270,000 times farther away than this!
For the sun to appear so bright and feel so warm to us from such a distance, it must be very big and very hot. The sun is actually so big that 109 Earths could fit across it, and 1,300,000 Earths could fit inside it. The sun has around 333,000 times as much mass as the Earth, and contains 99.86 percent of all the mass in the entire solar system.
The sun is also incredibly hot, with a surface temperature of about 10,000 degrees Fahrenheit (5,500 degrees Celsius). The temperature at the center of the sun is even higher, where it reaches 27 million degrees Fahrenheit (15 million degrees Celsius). The extremely high temperatures and pressures in core of the sun force hydrogen atoms to smash together and form helium. Every second, 600 million tons of hydrogen are converted into helium. This creates an enormous amount of energy. This energy powers the sun and creates its light and heat.
The heat from the sun powers our weather and keeps us warm. Its light is used by plants to provide food for life on Earth. Plants also use energy from the sun to create the oxygen we breath. Without the sun, Earth would be a dark and frozen planet where no life could exist. So, the sun may be just an average star, but for us it is the most important star of all!
To learn more about how our sun compares to other stars, visit the NASA Space Place: http://spaceplace.nasa.gov/sun-compare/
Artist’s concept of the size of planets compared with the size of the sun.
Image credit: NASA
An image of the sun from NASA’s Solar Dynamics Observatory.
Image credit: NASA/SDO