Chapter Introduction
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A montage of the planets (plus Pluto, a dwarf planet) in our solar system presented in correct relative sizes. The orbits in the background are also drawn to scale. (NASA)Formation of the Solar System
WHAT DO YOU THINK?
How many stars are there in the solar system?
Were the Sun and planets among the first generation of objects created in the universe?
How long has Earth existed, and how do we know this?
Answers to these questions appear in the paragraphs beside the corresponding circled numbers in the margins and at the end of the chapter.
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In this chapter you will discover
how the solar system formed
why the environment of the early solar system was much more violent than it is today
how astronomers define the various types of objects in the solar system
the relationships between planets, dwarf planets, small solar system bodies, and other classifications of objects in the solar system
how and why the planets are grouped as they are
how the moons formed throughout the solar system
the composition of the debris scattered throughout the solar system