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Minding the heavens the story of our discovery of the milky way
[...]... universes composed of stars like our Sun might appear as milky disks or circles Kant was not far off the mark: as we shall see in chapter 2, a few of the nearest galaxies do appear as cloudy spots, even to the unaided eye The story of our discovery of the Milky Way and other galaxies is in many ways the chronicle of the popularity, demise, and renewal of the theory of island universes None of the astronomers... the last star of the handle away from the dipper cup, lies about twice as far away as Dubhe, the uppermost of the two stars in the outer edge of the cup In the mind’s eye, we see the stars projected on a twodimensional plane 21 MINDING THE HEAVENS The Milky Way The band of light we call the Milky Way arches across the sky like a river of light, narrow in some places, wide and irregular in others Its hazy... Andromeda The stars along the side of the ‘‘V’’ nearest to Cassiopeia are dimmer than those of the opposite branch The ‘‘V’’ terminates in the Great Square of Pegasus, another well-known constellation The trick to finding the nebula is to 15 MINDING THE HEAVENS locate the second pair of stars defining the ‘‘V’’ (down from the open end of the letter) and to look to the right about the same distance away as the. .. even the history of our spiral disk galaxy, the Milky Way; and we learned at the same time that our magnificent system has its counterparts both near and far, in the billions of galaxies stretching into remote space and distant time 13 2 THE NAKED-EYE VIEW OF THE SKY ‘‘No more of the universe is visible to our unaided eyes than to the eyes of our Neanderthal ancestors But science, the product of our. .. the Earth The most important clue to the distribution of stars is the phenomenon we call the Milky Way The term ‘ Milky Way ’ has two possible, related meanings: it refers to our home galaxy, and it also means the misty band of milky- white light we see arching across the sky (figure 1.2) Residents of countries in the northern hemisphere see the Milky Way band of light most prominently in the late summer,... could study our own galaxy without thinking about the ramifications of his conclusions for the island universe theory The theory of island universes itself is a minor character in the drama of our understanding of the Milky Way and other galaxies, always in the background, sometimes moving into the spotlight Only very recently, in the middle of the twentieth century, did we come to appreciate the size,... lining of the ‘‘celestial sphere.’’ If you lie on your back and gaze upward at the stars in some quiet, dark location, you might even feel that you can sense the slow rotation of the sphere, carrying the stars across your field of view from east to west, and slinging them underneath you on the other side of the Earth The apparent daily movement of the sky is, of course, due to the rotation of the Earth,... are looking out of the disk of the Galaxy and into ‘‘deep space.’’ Southern hemisphere observers have a better view of the Milky Way overall, and see a particularly dazzling show in the southern hemisphere winter In July, when Scorpius is nearly overhead, the Milky Way stretches from southwest to northeast The irregular dark clouds cleaving the Milky Way into two 22 The Naked-Eye View of the Sky uneven... telescope and ‘‘mind the heavens ’ for him.2 The story of the discovery of our own and other galaxies unfolds through the lives of seven astronomers—and their assistants—who worked on the question of where we live in the cosmos I was motivated to tell the story through a series of biographies in part by my own desire to know more about the astronomers who have shaped our view of the universe Why did Wilhelm... would result in the view we have of the Milky Way By Herschel’s time already, astronomers understood that the stellar system or galaxy has the shape of a watch, wide and flat Not until the twentieth century, however, did astronomers have the means to map our own galaxy reliably from within Early theories of the universe The crowding of stars in the narrow band of sky we call the Milky Way suggests a