Prologue

Astronomy is the study of the sky, the science of cosmic objects and celestial happenings. It’s nothing less than the investigation of the nature of the universe we live in. Astronomers carry out the business of astronomy by looking and (for radio astronomers) listening. Astronomy is done with backyard telescopes, huge observatory instruments, and satellites orbiting Earth or positioned in space near Earth or another celestial body, such as the moon or a planet. Scientists send up telescopes in sounding rockets and on unmanned balloons; some instruments travel far into the solar system aboard deep space probes; and some probes gather samples with the aim of returning them to Earth.

Astronomy can be a professional or an amateur activity. About 15,000 professional astronomers engage in space science worldwide. Over 300,000 amateur astronomers live in the United States alone. And amateur astronomy clubs are everywhere.

Professional astronomers conduct research on the sun and the solar system, the Milky Way galaxy, and the universe beyond. They teach in universities, design satellites in government labs, and operate planetariums. They also write books, like this one (but maybe not as good). Most hold PhDs, and nowadays — so many of them study abstruse physics or work with automated, robotic telescopes — they may not even know the constellations.

Amateur astronomers know the constellations. They share an exciting hobby. Some stargaze on their own, and thousands more join astronomy clubs and organizations of every description. The clubs pass on know-how from old hands to new members, share telescopes and equipment, and hold meetings where members tell about their recent observations or hear lectures by visiting scientists.

Amateur astronomers also hold observing meetings where everyone brings a telescope (or looks through another observer’s scope). The amateurs conduct these sessions at regular intervals (such as the first Saturday night of each month) or on special occasions (such as the return of a major meteor shower each August or the appearance of a bright comet like Hale-Bopp). And they save up for really big events, such as a total eclipse of the sun, when thousands of amateurs and dozens of pros travel across Earth to position themselves in the path of totality to witness one of nature’s greatest spectacles.

This blog explains all you need to know to launch into the great hobby of astronomy. And it gives you a leg up on understanding the basic science of the universe as well. The latest space missions will make more sense: You’ll understand why NASA and other organizations send space probes to planets like Saturn, why robot rovers land on Mars, and why scientists seek samples of the dust in the tail of a comet. You’ll know why the Hubble Space Telescope peers out into space and how to check up on other space missions. And when astronomers show up in the newspaper or on television to report their latest discoveries — from space; from the big telescopes in Arizona, Hawaii, Chile, and California; or from other observatories around the world — you’ll understand the background and appreciate the news. You can even explain it to your friends.

Read only the parts you want, in any order you want. I explain what you need as you go. Astronomy is fascinating and fun, so keep reading. Before you know it, you’ll be pointing out Jupiter, spotting famous constellations and stars, and tracking the International Space Station as it whizzes by overhead. The neighbors may start calling you “stargazer.” Police officers may ask you what you’re doing in the park at night or why you’re standing on the roof with binoculars. Tell ’em you’re an astronomer. That’s one they probably haven’t heard (I hope they believe you!).