The Center of Our Solar System
Have you ever been outside on a hot summer day and wished the sun was just a little cooler or just a little farther away? Like it or not, the sun is vital to our existence here on Earth. The sun’s energy keeps our planet at just the right temperature to support life and allow us to grow food. It even keeps the earth spinning year after year. For all that the sun does for us, maybe it’s worth learning a little bit more about it.
It’s NOT All About Earth
For a long time, people believed the earth stood at the center of the universe and everything, including the sun, revolved around it. This belief is called geocentrism. Geocentrism was an accepted truth until the Polish astronomer Nicolaus Copernicus came along. In 1543, Copernicus proved through his observations and mathematical calculations that the earth actually revolved around the sun. This view is called heliocentrism. Copernicus was not the first scientist to discover heliocentrism, but his book On the Revolutions of the Heavenly Spheres provided more detailed support behind the theory.
Other scientists built on his work. In 1609, Italian astronomer Galileo Galilei built the most powerful telescope of his time and used it to confirm heliocentrism. Unfortunately, the Catholic Church, which was a major power in Europe, supported the more commonly-held theory of geocentrism. The Roman Inquisition questioned Galileo and accused him of heresy. In 1633, they sentenced him to life under house arrest. But Galileo continued to write. His work was so influential that he is often called the “father of modern physics.”
Heliocentrism became widely accepted over the next century, and eventually the Church stopped resisting. Scientists could freely study the skies and our star, the sun.
One of Many Stars
The sun is a star, just like the other millions of stars you see when you look at the night sky. In fact, the sun is a relatively normal star. Like all stars, it is a large ball of gas that produces huge amounts of energy. Stars form when particles floating in space are drawn closer together by gravity, until the cloud of space dust is round and dense. Inside that dense center, hydrogen atoms are under so much pressure that they fuse together into helium atoms. This process is called nuclear fusion, and it releases a lot of extra energy in the forms of heat and light. Nuclear fusion is what keeps stars burning.
A Whole New World
4.5 billion years ago, when the sun formed, it was not the only clump of gas and dust swirling around space. As the sun’s particles pulled together, other particles and clouds farther away began circling around it, too. Those clouds started condensing into planets. The process was dramatic. Clumps of space dust slammed into each other, breaking apart and reforming, over millions of years. Finally, they solidified into the eight planets we know today. Without the sun and its powerful gravity, the earth may not be here!
The Sun: The Center of Attention
The sun sits at the center of our solar system. The solar system includes the sun and everything that circles around it: the eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), their moons, and asteroids. The sun is so huge that it accounts for over 98% of all of the mass in the solar system; the pull of its gravity is incredibly strong. All of the planets are stuck circling in this gravitational field, orbiting the sun. Imagine tying a weight to one end of a string, then holding the other end of the string in your hand and spinning the weight around. The weight is orbiting your hand. The sun holds the whole solar system together in a similar way.
The one big difference between the weight on your string and the planets is that each planet’s orbit is actually an oval, or an ellipse, not a circle. This theory was popularized in the early 1600s by Johannes Kepler, a German mathematician and astronomer. Kepler’s laws of planetary motion, as well as Isaac Newton’s law of gravity, supported Copernicus’ theory that the sun was the center of the solar system because it explained how the sun held other planets in orbit.
Putting It in Perspective
Even though it acts just like any other star, the sun is extremely important to us here on Earth. Here are some more things to know about our sun:
1. It is actually pretty big. Scientists estimate that, by mass, it is in the top 10% of all stars.
2. It is about 4.5 billion years old. Think about this: humans have been around for about 200,000 years, so humans have existed for only 0.00004 percent of the sun’s life.
3. Sun is about halfway through its supply of hydrogen. This means that in another 4.5 billion years, it will run out of hydrogen and swell into a different kind of star that cannot sustain life on Earth.
4. The sun’s core is about 27 million degrees Fahrenheit. Compare that to Earth’s core at about 11,000 degrees Fahrenheit.
5. The volume of the sun is about 1,409,272,569,059,860,000 km3. That means 1.3 million Earths could fit inside it.
The sun helps us in more ways than we can count. Its gravitational pull helped form the earth and keeps our planet spinning. Its nuclear fusion keeps us warm and gives us light to grow our food. It holds our solar system together! No wonder so many of scientists have dedicated their lives to figuring out how it works.