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The Milky Way

The Milky Way: An Insider's Guide

William H. Waller
Copyright Date: 2013
Pages: 296
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  • Book Info
    The Milky Way
    Book Description:

    This book offers an intimate guide to the Milky Way, taking readers on a grand tour of our home Galaxy's structure, genesis, and evolution, based on the latest astronomical findings. In engaging language, it tells how the Milky Way congealed from blobs of gas and dark matter into a spinning starry abode brimming with diverse planetary systems--some of which may be hosting myriad life forms and perhaps even other technologically communicative species.

    William Waller vividly describes the Milky Way as it appears in the night sky, acquainting readers with its key components and telling the history of our changing galactic perceptions. The ancients believed the Milky Way was a home for the gods. Today we know it is but one galaxy among billions of others in the observable universe. Within the Milky Way, ground-based and space-borne telescopes have revealed that our Solar System is not alone. Hundreds of other planetary systems share our tiny part of the vast Galaxy. We reside within a galactic ecosystem that is driven by the theatrics of the most massive stars as they blaze through their brilliant lives and dramatic deaths. Similarly effervescent ecosystems of hot young stars and fluorescing nebulae delineate the graceful spiral arms in our Galaxy's swirling disk. Beyond the disk, the spheroidal halo hosts the ponderous--and still mysterious--dark matter that outweighs everything else. Another dark mystery lurks deep in the heart of the Milky Way, where a supermassive black hole has produced bizarre phenomena seen at multiple wavelengths.

    Waller makes the case that our very existence is inextricably linked to the Galaxy that spawned us. Through this book, readers can become well-informed galactic "insiders"--ready to imagine humanity's next steps as fully engaged citizens of the Milky Way.

    eISBN: 978-1-4008-4737-2
    Subjects: Astronomy, Physics

Table of Contents

    (pp. vii-xiv)
    William H. Waller
    (pp. 1-9)

    Imagine yourself on a magic carpet, levitating away from Earth on a voyage into deep space. As you begin your ascent, you can see ever enlarging vistas of land and sea beneath you. Very soon, the terrestrial horizon begins to curve and fall away. Your initial concept of a straight horizon that segregates Earth from sky has become nonsensical. Instead, you see your home orb shrinking ever smaller, and the starry sky enlarging to fill the expanse. As your flying tapestry propels you beyond the inner Solar System, your view of the Sun also begins to take up less and...

    (pp. 10-52)

    Humans have marveled at the Milky Way for as long as they have roamed the surface of Earth. Indeed, the ancient hominids of the African savannah enjoyed views of the Milky Way that were far superior to those experienced by most of us in the modern world. Blessed with dry, clear skies that were free of light pollution, these earliest sky gazers and their later descendents have born witness to the Milky Way for hundreds of millennia. To ponder the Milky Way today is to share our cosmic wonder with these primeval astronomers, and in doing so, to commune with...

    (pp. 53-81)

    It is strangely unsettling to peer through a telescope at faint patches of starlight and nebulosity. Despite the modern telescope’s extraordinary powers, the stiletto stars defy magnification. Instead, the telescopic viewer is confronted with starscapes of numerous shimmering points—each point representing a completely inscrutable solar system. The nebular smudges do manage to resolve into diaphanous forms—as colorless and ethereal as phantoms on a midnight romp. Distant, myriad, and uncaring, these uncanny sights elude human negotiation. No wonder so many people choose to keep their porch lights on.

    Yet this same aloofness is what draws astronomers to poke and...

    (pp. 82-101)

    The Great Spirit must have been especially magnanimous when creating the Milky Way Galaxy.¹ Spanning more than 100,000 light-years and containing more than 100 billion stars, the Milky Way rules over the Local Group of galaxies in a shared arrangement with Messier 31—the great Nebula in Andromeda. Together, these two giant spiral galaxies account for more than 85 percent of the luminous matter in the Local Group—with the other forty-odd galaxies swarming about their two massive hosts like bees around twin hives.

    We have learned of these amazing proportions through the classic astronomical task of determining distances to...

    (pp. 102-126)

    As we look beyond the meek stars of the solar neighborhood and past the dazzling upstarts in Gould’s Belt, our view of stars in the galactic disk becomes increasingly compromised by the obscuring effects of interstellar dust. This irregular smokescreen puts a limit on how far we can see at visible wavelengths. In directions away from the murky Milky Way, our views become much clearer, allowing us to spy globular star clusters more than 50,000 lightyears from us. This ability allowed Harlow Shapley to determine in 1920 that the system of globular clusters was centered well away from the Sun...

    (pp. 127-147)

    To an astronomer, the birth of a star is as miraculous as the birth of a child. Both creative processes begin with essentially nothing and culminate in fully formed wonders—as exquisite as they are expressive. Of course, there are important differences between spawning baby humans and infant stars. For starters, the gestation of a human begins with a tiny fertilized egg that then draws on the mother’s placenta for all of its material and energetic needs. Stars do not form from such minuscule seeds that subsequently subdivide, feed on their surroundings, and grow into animate complexes populated by more...

    (pp. 148-170)

    One of the greatest achievements of astronomers during the last century was to discover how and then understand why the lives of stars critically depend on the stars’ endowed masses. Throughout their “normal” main-sequence phase and more peculiar giant phases, stars illuminate and evolve according to the masses that were allotted them at birth. Only in instances where two closely interacting binary stars exchange mass is this natal determinism compromised. But a star’s mass-ordained trajectory of luminosity, color, size, and longevity does not really do justice to its individuality. So before we consider the evolution of stars according to their...

    (pp. 171-193)

    Nothing lasts forever, not even stars. In their deaths, stars leave behind fleeting nebulae of diaphanous beauty along with much longer-lasting compact remnants whose bizarre properties defy our Earth-bound imaginings. These nebular and stellar exotica play peculiar but vital roles within their hosting galaxies. Once again, stellar mass determines what ensues. We can see in figure 8.1 a road map of the different legacies that result from differing stellar masses. From white dwarfs, to neutron stars and black holes, myriad weird residues of stellar lives can be found populating the Milky Way’s disk and halo. Meanwhile, the enriched effluvia of...

    (pp. 194-220)

    In the course of this book, we have encountered myriad stars of differing mass, color, size, luminosity, composition, age, and activity; clusters of stars in various configurations and stages of evolution; cold, dusty clouds pregnant with embryonic stellar and planetary systems; emission nebulae irradiated by hot young stellar upstarts; and other emission nebulae powered by bizarre stellar remnants—including white dwarfs, neutron stars, and black holes. Together, these variegated species inhabit the Milky Way, co-evolving and interacting as parts of a vast galactic ecosystem. The picture of a galactic garden (or jungle!) comes to mind, as it provides a helpful...

    (pp. 221-235)

    Like some sleeping giant, the core of our Galaxy softly snores beneath thick blankets of dust. This somnolent situation was not always the case, however, nor will it be in the future. Just consider what lurks within the central light-year, and you can begin to appreciate the incredible power inherent to the Galaxy’s dark heart. In this chapter, we will survey (from a safe distance) the many unique phenomena that have been found in the general direction of the galactic center. We will then vicariously zoom into the core as far as our observations permit, assess the case for a...

    (pp. 236-250)

    How far back in time must we go in order to perceive the Milky Way’s origins? If our estimated ages for various constituents of the Milky Way are correct, we pretty much have to go all the way back to the Hot Big Bang itself, some 14 billion years ago (see figure 11.1). Consider the lowly hydrogen atom, the most abundant substance making up our Galaxy’s stars and nebulae. Its single proton was likely forged from a triplet of quarks around a millionth of a second following the Big Bang—as the primeval fireballcooledto a temperature of a...

    (pp. 251-276)

    In the last eleven chapters, this book has presented the Milky Way in all its material diversity, spatial complexity, and temporal mutability. While writing these chapters, I have intentionally endeavored to portray our home galaxy as a living, breathing “organism”—one that emerged from the chaos of the Hot Big Bang some 12 billion years ago, and that is still very much alive with the fertile pyrotechnics of star-birth and star-death. What remains is an attempt to connect all these galactic theatrics to the emergence of our very selves—and perhaps to other life-forms that may be squiggling hither and...