Confirming Pages

xxvi Preface

The Unit format also provides an opportunity to take some extra steps beyond the ordinary text. The authors have included some material of special interest that introduces topics most introductory texts do not offer—for example, Units on cal-endar systems and special relativity. More advanced material within a particular Unit topic is also organized toward the end of the Unit so that the essentials are covered first—also providing flexibility for assigning readings.

Pathways to Astronomy makes it easy to tailor readings and exercises so they fit best within a course’s structure. It also provides opportunities to travel down some fascinating paths to enhance a course or to provide additional reading for advanced students.

NEW TO THE FOURTH EDITIONNew Book Elements In our efforts to help students understand and interpret this wide-ranging material, we have added several new elements to Pathways:

Learning Objectives: At the start of each Unit, a new list of learning objectives describes the most important skills and abilities that readers should strive for in studying that Unit. These identify specific actions (such as describing, explaining, comparing, and calculating) that demonstrate a good mastery of the material.

Mathematical Insights: These marginal notes provide mathematical details to clarify the discussion in the text or expand beyond it, and they provide worked examples of mathematical problems.

New map format: We have converted almost every global map of the Earth, Moon, and planets to a Mollweide equal-area projection. Data are frequently released in a wide variety of projections, which introduce different distortions. Repro-cessing the data into a single format facilitates comparisons between planets, and the equal-area projection avoids distortions that exaggerate sizes in polar regions.

Mathematical Insight

New boxes in the margins explore the mathematics of the text more deeply

These marginal notes identify objects related to the text that can be seen in the Looking Up images at the front of the book —or with a small telescope.

LO O K I N G U P

Aphrodite Terra

Ishtar Terra

MaxwellMontes

AtalantaPlanitia

LaviniaPlanitia

Guinevere Planitia

Sedna Planitia

Aino Planitia

AlphaRegio

Atla Regio

Lada Terra

LakshmiPlanum

Maat Mons

BetaRegio

+8 km0 km−8 km

Elevation

Idunn Mons

Niobe Planitia

Looking Up Icons: These marginal notes point out objects that can be seen in the Looking Up pages at the front of the book, helping to relate the textual descrip-tions to objects visible in the night sky.

End-of-Unit questions: We have revised and added new questions to each Unit.

sch12249_fm_i-xxxvi.indd xxvisch12249_fm_i-xxxvi.indd xxvi 26/10/13 1:49 AM26/10/13 1:49 AM

Confirming Pages

Preface xxvii

Highlights of Changes In addition to our own monitoring of new and interesting results in the field, many readers and reviewers offered excellent suggestions for updates and improvements to Pathways. In all, more than 150 figures were added, updated, or replaced throughout the book to improve clarity and to include some of the best new images available. The Unit topics remain the same as the third edition, although a few Units were more extensively revised as noted below. The following is a partial list of changes, including the most interesting updates and additions:Unit 4 Foundations of Astronomy: Revised text and new figures for particles and

forces, with brief discussion of the Higgs particle. Unit 6 The Year: Revised discussion of seasons, and added figures of the Karnak

temple in Egypt and path of Sun as seen from different latitudes. Unit 8 Lunar Cycles: Revised eclipse text and figures and new eclipse-path map. Unit 10 Geometry of the Earth, Moon, and Sun: New figures illustrating Earth’s

curvature and ancient ideas of parallax. Unit 19 Tides: Revised figures to clarify tidal interactions. Unit 22 The Electromagnetic Spectrum: New figure with a multiwavelength

comparison of M31. Unit 23 Thermal Radiation: New figures with graphs illustrating the Wien and

Stefan-Boltzmann Laws. Unit 32 The Earth’s Atmosphere and Space: New figures and images of atmo-

spheric refraction. Unit 33 Amateur Astronomy: Updated images and discussion of amateur astro-

nomical photography. Unit 34 The Structure of the Solar System: Revised discussion and table of chem-

ical compositions in Solar System. Unit 35 The Origin of the Solar System: Added graph of radioactive decay. Unit 36 Other Planetary Systems: Extensively revised with new figures to illus-

trate exoplanet detection methods, planet migration, density determinations, and recent Kepler findings.

Unit 37 The Earth as a Terrestrial Planet: New figures and expanded discussion in section 3 on tectonics.

Unit 38 Earth’s Atmosphere and Hydrosphere: Revised figures and text on Cori-olis effect (section 5).

Unit 39 Our Moon: Reorganized section order, beginning now with the Moon’s formation. Many new figures and images from LRO and Lunar Prospector.

Unit 41 Venus: Added recent findings from Venus Express, and reprocessed imag-ery from Magellan.

Unit 42 Mars: Unit extensively updated and reorganized, adding several new and reprocessed images, for clearer development. Early results and images from Curiosity included.

Unit 43 Asteroids: New comparison images including Vesta results from Dawn. Unit 47 Satellite Systems and Rings: New Cassini images of Enceladus and

rings. Unit 49 Comets: Unit reorganized for clearer development with several revised

diagrams and new images from Stardust and STEREO. Unit 50 Impacts on Earth: Added Images from the Chelyabinsk meteor explosion. Unit 51 The Sun, Our Star: New diagram of Voyagers nearing interstellar boundary. Unit 54 Surveying the Stars: New image and discussion of finding Sun’s distance

from the transit of Venus. Unit 59 The H-R Diagram: Some details removed from H-R diagrams to make

them easier to understand. Unit 68 Neutron Stars: Updated discussion of recent observations of nearby neu-

tron stars and implications for their internal structure.

sch12249_fm_i-xxxvi.indd xxviisch12249_fm_i-xxxvi.indd xxvii 26/10/13 1:49 AM26/10/13 1:49 AM

Confirming Pages

M51The Whirlpool Galaxy can be seen as a dim patch of light with a small telescope. M51 is about 37 million ly away from Earth (Unit 76).

170,000 ly

Mizar and AlcorIf you look closely at it, you may notice that the middle star in the “handle” is actually two stars — Mizar and Alcor. Despite appearing close together in the sky, they are probably not in orbit around each other. However, with a small telescope, you can see that Mizar (the brighter of the star pair) has a faint companion star. This companion does in fact orbit Mizar. Moreover, each of Mizar‘s stars is itself a binary star, making Mizar a quadruple system (Unit 57).

Polaris

Little Dipper

Poin

ter s

tars

Big Dipper

Circling in the northern sky is the Big Dipper, part of the well-known constellation Ursa Major, the Big Bear. The Big Dipper is technically not a constellation, but just an asterism — a star grouping. It is easy to see in the early evening looking north from mid-March through mid-September. The Big Dipper can help you find the North Star, and with a telescope on a dark, clear night, you can find several other intriguing objects as shown below.

M97 — The Owl This planetary nebula (Unit 65) is ~2500 ly away.

~1.6 ly

Location of the Hubble Deep Field(Unit76)

Over the course of a night, stars appear to rotate counterclockwise around the star Polaris, which remains nearly stationary because it lies almost directly above Earth’s North Pole. Polaris is not especially bright, but you can easily find Polaris by extending a line from the two stars at the end of the bowl of the Big Dipper, the pointer stars, as shown by the dashed yellow line (Unit 13).

Big Dipper in 3-D

1 light year (ly) ≈ 10 trillion km ≈ 6 trillion miles

Earth

80 ly123 ly

83 ly80 ly

104 ly86 ly

83 ly

Ursa MajorLooking Up #2

xxviii Preface

Unit 69 Black Holes: New section on Hawking radiation. Unit 70 Star Clusters: New images of clusters showing them to the same scale. Unit 74 Mass and Motions in the Milky Way: Added Fermi observations of

gamma-ray bubbles and updated observations of orbits around central black hole.

Unit 79 Dark Matter: Added discussion of recent possible WIMP detections. Unit 80 Cosmology: New image and discussion of tentative detections of galaxies

at redshift greater than 10. Unit 84 Dark Energy and the Fate of the Universe: New diagrams and updated

cosmological parameters with results from Planck. Unit 85 Astrobiology: Updated with recent microfossil findings. Unit 86 The Search for Life Elsewhere: Added early Curiosity findings on Mars.

FEATURESLooking Up Illustrations It can be challenging to link introductory astronomy to the sky around us. The nine “Looking Up” full-page art pieces at the front of the book provide another pathway to astronomy, connecting what we actually see when “looking up” at the night sky with the more theoretical side of astron-omy. Each illustration displays a large-scale photograph of one or more constel-

lations in the night sky. Each also contains close-up photographs and illustrations of some of the most interesting telescopic objects with cross-references to the text. Details are also given regarding the objects’ distances from Earth, along with three- dimensional illustrations of some of the stars or other objects within the field of view. The Looking Up Illustrations begin on page ii, to make them easier to find.

Star Chart A good star chart also helps link the study of astronomy to the night sky. Pathways to Astronomy offers a foldout star chart as well as seasonal star charts for Northern Hemisphere observers. These will help students to take that next step beyond the book—exploring the night sky.

Detailed Art Pathways to Astronomy has taken each illustration a step further than the norm. Many fig-ures are annotated to describe the processes depicted within the illustration. Photos are often inserted next to the illustration for comparison so students can see the process in reality.

End-of-Unit Material The end-of-unit sections include hundreds of Key Points, Review Questions, Quantitative Problems, and Test Yourself questions to help students master the unit material. These ele-ments allow students to apply what they have learned before moving on to another unit. The answers for all the Test Yourself questions are provided at the back of the text.

sch12249_fm_i-xxxvi.indd xxviiisch12249_fm_i-xxxvi.indd xxviii 26/10/13 1:49 AM26/10/13 1:49 AM