You may wonder, does every object spinning around in the solar system have periods of daylight and dark? Most of the planets, their moons, and the other rotating objects actually do. Earth's solar day, with one sunrise and sunset, takes twenty-four hours to complete. Mercury, on the other hand, has a sunrise and then must wait until its next year for the sunset! Earth rotates from the West to the East, but several of the planets don't. So if you landed on one of them, it would be just the opposite and you would see the sun rising in the West and setting in the East! Can you guess how many times a year the sun has a sunrise or sunset? If you said never, you're right. The sun is always shining itself, even you can't see it from where you are, so it never has a night. It takes less than thirty Earth days for the sun to complete a rotation around its own equator, while its poles take more than thirty days. Are you wondering how this can be? It's because the sun is made of gas.
If someone asked you what was the most interestingfeature on the surface of the sun, what would you say? Most people would probably say the sun's spots.
Ribbons of Light
Explosions on the surface of the sun, called “solar flares,” shoot enormous amounts of energy into space. When masses of particles from a solar flare hit Earth's atmosphere near the North Pole, they cause flickering ribbons of light to dance across the sky. Astronomers call this amazing sight the aurora borealis. Break the number code to learn the more familiar name!
Astronomers keep a close eye on these sunspots, which seem to increase their numbers in approximatelyeleven-year cycles. These spots, which move across the surface of the sun, allow them to keep track of the number of rotations the sun makes. They think the spots are proof of an intense magnetic force that moves from the center of sun to the outside surface. Once it reaches the surface it radiates as energy to the rest of the solar system. This energy from the sun also creates a strong solar wind that cleaned the areas around the planets after they were formed and still carries magnetic particles to them.