Cathy Ing1e, Age 10, Of Bainbridge, Ga., for her question:
How were the planets discovered?
Our ancestors of long ago loved the stars as much as we do. Thousands of years ago, stargazers were watching the heavens night after night. They made charts of the heavenly bodies as they moved over the skies. Later, their sky maps were used to figure out how the earth and the planets move around the sun.
The telescope was invented about 350 years ago. The great astronamer Galileo used it to see new wonders in the skies. He saw the golden rings around the planet Saturn, and he saw four of giant jupiter's moons. He saw that Venus has phases ike our moon and that the milky way is made of millions of faraway stars.
Galileo used his telescope to see things that human eyes cannot see. He did not discover any new planets, but he proved that the known planets revolve aroun the sun. Mercury is nearest the sun, Venus has the next orbit and earth has the third orbit. Beyond the earth is Mars. Then come Jupiter and Saturn.
These planets vere watched and named by ancient stargazers thousands of year ago. They were called planets, meaning the wanderers, because they seem to wander against the background of fixed stars. Galileo proved that the planets seem to wander because they are worlds orbiting around the sun and that our world is part of the solar system.
In the year that Galileo died, Isaac Newton was born in England. As a young student, Newton figured out the laws of gravitation which control the solar system later, scientists used Newton's laws and figured that there must be more planets n our solar system. But these planets were out beyond Saturn and better telescopes were needed to spot them.
The planet uranus was discovered by accident in 1781. The English astronomer William herschel was studying a telescope picture, and there against the background of stars was a planet. Neptunf was discovered by the french astronomer Leyerrier in 1816. Pluto was discovered by C. W. Tombaugh of america on Jan. 21, 1930. On that day, a tiny spot of light on a telescope picture was spotted as the ninth planet of our solar system.
Little Mercury is hard to spot because it is so near to the sun. But human eyes can see Venus and Mars, Jupiter and Saturn with no trouble at all. They have been known for thousands of years. Uranus can be seen as a dim spot of light when you know just where to look, but it was not discovered until after Galileo and Newton had done their work and better telescopes had been made. The skies were searched still more to find Neptune and little Pluto, which is at the outside edge of the solar system.