Astronomy For Dummies - Maran Stephen P.

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skip if you just want to know the basics and start watching the skies. The scientific background can be good to know, but many people happily enjoy their stargazing without knowing about the physics of supernovas, the mathematics of galaxy chasing, and the ins and outs of dark energy.

      

This lightbulb puts you right on track to make use of some inside information as you start skywatching or make progress in the hobby.

      

How much trouble can you get into watching the stars? Not much, if you’re careful. But some things you can’t be too careful about. This icon alerts you to pay attention so you don’t get burned.

      Beyond the Book

      In addition to the book you’re reading right now, be sure to check out the free Cheat Sheet online. It offers a timeline of notable astronomical events and a list of famous female astronomers. To get this Cheat Sheet, simply go to www.dummies.com and enter “Astronomy For Dummies” in the Search box.

      If you want to test your astronomy knowledge, check out the practice quizzes online. Each chapter has a corresponding quiz consisting of multiple choice and true/false questions. I’ve also turned the glossary into flashcards that let you test your knowledge of astronomy terms.

      To gain access to the online content, all you have to do is register. Just follow these simple steps:

      1. Find your PIN access code.

      ● Print book users: If you purchased a hard copy of this book, turn to the inside front cover to find your PIN.

      ● E-book users: If you purchased this book as an e-book, you can get your PIN by registering your e-book at dummies.com/go/getaccess. Go to this website, find your book and click it, and answer the validation questions to verify your purchase. Then you’ll receive an email with your PIN.

      2. Go to Dummies.com and click Activate Now.

      3. Find your product (Astronomy For Dummies, 4th Edition) and then follow the on-screen prompts to activate your PIN.

      Now you’re ready to go! You can come back to the program as often as you want – simply log on with the username and password you created during your initial login. No need to enter the access code a second time.

       Tip: If you have trouble with your PIN or can’t find it, contact Wiley Product Technical Support at 877-762-2974 or go to http://support.wiley.com.

      Your registration is good for one year from the day you activate your PIN. After that time frame has passed, you can renew your registration for a fee. The website gives you all the details about how to do so.

      Where to Go from Here

      You can start anywhere you want. Worried about the fate of the universe? Start off with the Big Bang (see Chapter 16 if you’re really interested).

      Or you may want to begin with what’s in store for you as you pursue your passion for the stars.

      Wherever you start, I hope you continue your cosmic exploration and experience the joy, excitement, enlightenment, and enchantment that people have always found in the skies.

Part 1

      Getting Started with Astronomy

      IN THIS PART …

      Discover the basic elements of astronomy, check out a list of constellations, and get a crash course on gravity.

      Find out about the resources available to help you check out the night sky, including organizations, facilities, and equipment.

      Get an introduction to astronomical and artificial phenomena that sweep across the night sky, such as meteors, comets, and artificial satellites.

      Chapter 1

      Seeing the Light: The Art and Science of Astronomy

      IN THIS CHAPTER

      ❯❯ Understanding the observational nature of astronomy

      ❯❯ Focusing on astronomy’s language of light

      ❯❯ Weighing in on gravity

      ❯❯ Recognizing the movements of objects in space

      Step outside on a clear night and look at the sky. If you’re a city dweller or live in a cramped suburb, you see dozens, maybe hundreds, of twinkling stars. Depending on the time of the month, you may also see a full Moon and up to five of the eight planets that revolve around the Sun.

      A shooting star or “meteor” may appear overhead. What you actually see is the flash of light from a tiny piece of space dust streaking through the upper atmosphere.

      Another pinpoint of light moves slowly and steadily across the sky. Is it a space satellite, such as the Hubble Space Telescope, the International Space Station, or just a high-altitude airliner? If you have a pair of binoculars, you may be able to see the difference. Most airliners have running lights, and their shapes may be perceptible.

      If you live in the country – on the seashore away from resorts and developments, on the plains, or in the mountains far from any floodlit ski slope – you can see thousands of stars. The Milky Way appears as a beautiful pearly swath across the heavens. What you’re seeing is the cumulative glow from millions of faint stars, individually indistinguishable with the naked eye. At a great observation place, such as Cerro Tololo in the Chilean Andes, you can see even more stars. They hang like brilliant lamps in a coal black sky, often not even twinkling, like in van Gogh’s Starry Night painting.

      When you look at the sky, you practice astronomy – you observe the universe that surrounds you and try to make sense of what you see. For thousands of years, everything people knew about the heavens they deduced by simply observing the sky. Almost everything that astronomy deals with

      ❯❯ Is seen from a distance

      ❯❯ Is discovered by studying the light that comes to you from objects in space

      ❯❯ Moves through space under the influence of gravity

      This chapter introduces you to these concepts (and more).

      Astronomy: The Science of Observation

      Astronomy is the study of the sky, the science of cosmic objects and celestial happenings, and the investigation of the nature of the universe you live in. Professional astronomers carry out the business of astronomy by observing with telescopes that capture visible light from the stars or by tuning in to radio waves that come from space. They use backyard telescopes, huge observatory instruments, and satellites that orbit Earth collecting forms of light (such as ultraviolet radiation) that the atmosphere blocks from reaching the ground. They send up telescopes in sounding rockets (equipped with instruments for making high-altitude scientific observations) and on unmanned balloons. And they send some instruments into the solar system aboard deep-space probes.

      Professional astronomers study the Sun and the solar system, the Milky Way, and the universe beyond. They teach in universities, design satellites in government labs, and operate planetariums. They also write books (like me, your loyal For Dummies hero). Most have completed years of schooling to hold PhDs. Many of them study complex physics or work with automated, robotic telescopes that reach far beyond the night sky recognizable to our eyes. They may never have studied the constellations (groups of stars, such as Ursa Major, the Great Bear, named by ancient stargazers) that amateur or hobbyist astronomers first explore.

You may already be familiar with the Big Dipper, an asterism in Ursa Major. An asterism is a named star pattern that’s not identical to one of the 88 recognized constellations. An asterism may be wholly within a single constellation

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