Have you ever looked toward the sky? Of course you did! When you did look up, you saw the sun. It didn't look very large, did it? You can easily hide it from your sight with just one hand. Actually, it is a ball of hot gases so huge that it would take 1.3 million globes the size of earth to equal it. It is 865,000 miles in diameter.
Though the sun is 93 million miles away, it can burn your skin severely, and even blind you if you look directly at it. Deep inside the sun, the temperature is hotter than the hottest furnace. It is so hot that it heats and lights all the planets in our solar system.
The sun supplies nearly all of the earth's light, heat, and power.
The sun also has a force of gravity, which is extremely strong.
Planets would move in a straight line out into space forever if the sun's gravity didn't change their direction. The sun's gravity pulls the planet so that its straight motion becomes a curve. This makes the planet orbit around the sun. Because of the sun's pull of gravity, all the planets in our solar system revolve around it.
The Orbits of the Planets
Some planets orbit closer to the sun than others. And some are far away from the sun. The planets that are the farthest from the sun are called outer planets.
The
planets that are closest to the sun are called inner planets. The inner
planets are close to each other as well as close to the sun. There are
four inner planets:
Mercury
Venus
Earth
Mars
The inner planets have a hard, rocky surface. It is possible to land a spacecraft on planets that have this type of hard surface.
