The Nature of Planets, Dwarf Planets, and Space Objects

The Nature of Planets, Dwarf Planets, and Space Objects — page 7
THE NATURE OF PLANETS DARF PLANETS AND SPACE ORECTS Moon because the objects appeared to move across the background of the apparently fixed stars In some languages the names of these seven bodies are still connected with the days of the week In time astronomers learned more about how celestial objects move in the sky and they recognized that the Sun not Earth is the center of the solar sys tem The term planet came to be reserved for large bodies that orbit the Sun and not another planet so the Sun and Moon were no longer considered planets With the aid of telescopes modern astronomers have discovered hundreds of thousands of additional objects orbiting the Sun including more planets Although Uranus also is sometimes visible with the naked eye ancient astronomers were unable to distinguish it from the stars Uranus was first identified as a planet in 1781 The eighth planet Neptune was discovered in 1846 THE QUESTION OF PLUTO Pluto was initially considered a planet Indeed its discovery in 1930 was the result of a major search for a distant ninth planet Astronomers found that Pluto was unlike the other planets in many ways including its 12