From earliest times, humans have wondered about the sky above them. People looked at distant stars and wondered what they were made of. They wondered whether any other places in the universe were like Earth. At first people used simple telescopes to study the solar system-the Sun and all the planets that circle around it. Later, more powerful telescopes and high-tech machines allowed people to investigate worlds outside the solar system. In this book, we'll explore seven wonders beyond the solar system. We'll look at giant clouds of gas and dust called nebulae. Some nebulae are places where stars are born. Other nebulae are all that remains of stars that have died. Other wonders beyond the solar system include pulsing stars, giant stars, and giant clusters of stars called galaxies. We'll visit them all. And we'll explore the age-old question: Does the universe have any other planets like Earth? We'll learn about scientists who hunt for Earthlike planets and the tools they use. Finally, we'll look at the big picture-the universe itself. This vast network of stars, planets, and other objects is the biggest wonder of them all.
