(c) Anthony K. Grafton 2003

Our Solar System, Part 1: The Shining of the Sun

The Sun is the star at the center of our solar system and it provides essentially all the energy that sustains life on Earth. But how much do you know about the Sun? Do you know why the Sun shines?

If you total it all up, well over 99% of the matter in our solar system is contained in the Sun. All the planets, asteroids, and comets in our solar system orbit around the Sun (although it was once wrongly believed that the Sun orbited the Earth. And the Sun is big, really big. The Earth about 13,000 kilometers wide, but the Sun is almost 1.4 million kilometers wide. That means almost one-million Earth-sized planets could fit inside the Sun.

Besides being very large, the Sun is also very hot. The surface of the Sun is over 5500 ^oC, while temperatures at its center are over 15,000,000 ^oC. Compare this to a normal room temperature of about 22 ^oC.

The Sun is made almost entirely of hydrogen and helium, the two lightest elements in the Universe. But because there’s so much matter all together in one place, the gravitational forces at the center of the Sun are massive enough to squeeze pairs of hydrogen atoms together to form single helium atoms. This process is called nuclear fusion.

Nuclear fusion, the joining of two atoms to form one atom, produces incredible amounts of energy since some of the mass of the two combining atoms is converted to energy according to Albert Einstein’s famous “E=mc²” equation. The Sun consumes about 700 million tons of hydrogen every second through nuclear fusion and it produces about 400 billion billion megawatts of power.

The Sun has been shining for around 5 billion years, and it should continue to shine at least that much longer. Scientists have discovered many other types of stars, some of which are many thousands of times larger than our Sun, and some of which are many billions of years older. Over the past several years, astronomers have also discovered nearly 100 other stars besides our Sun that have planets around them, increasing the odds that life exists beyond the Earth. Can you find the names of some of the stars that are known to have planets?