Whitney - The Discovery of Our Galaxy

THIS IS A BORZOI BOOK
PUBLISHED BY ALFRED A. KNOPF, INC.

Copyright 1971 by Charles A. Whitney

All rights reserved under International and Pan-American Copyright Conventions.
Published in the United States by Alfred A. Knopf, Inc., New York, and simultaneously in Canada by Random House of Canada Limited, Toronto.
Distributed by Random House, Inc., New York.

eISBN: 978-0-307-81709-9
Library of Congress Catalog Card Number: 76154942

v3.1

Dedicated to my father,
Charles Smith Whitney,
whose life was a work of art

The solar system, according to Copernicus

Tycho Brahes observatory

Young stars and nebulosity

Hubbles variable nebula

Reflection of light from the outburst of Nova Persei 1901

The changing brightness of Cassiopeia

The outburst of a nova

Expanding nebulosity around Nova Persei 1901

Keplers scheme of the orbits of Jupiter and Saturn

Keplers garden sculpture

The Milky Way in the constellations Sagittarius, Ophiuchus, and Scorpius

An atlas of the Milky Way (photographic mosaic)

The Praesepe star cluster

Isaac Newton (16421727)

From cannon ball to artificial satellite (diagram by Newton)

The Andromeda Nebula

The central region of the Orion Nebula

The nebula M87

The globular star cluster M3

M16, a nebula with stars

Thomas Wrights model of the Milky Way

An alternative hypothesis by Wright

Wrights universe of galaxies

The binary star Krueger 60

William Herschels diagram of the earths orbit

The planet Uranus

Herschels 20-foot reflecting telescope

Herschels mammoth 40-foot telescope

Our galaxy according to Herschel

The Great Nebula in Orion

Nebulae in the constellation Hercules

Stefans Quintet (of nebulae)

Drawings by Herschel

Dark region in the Milky Way

The nebula N.G.C. 1514

Planetary nebula in the constellation Aquarius

Herschel as an old man

Pierre-Simon Laplaces Nebular Hypothesis

The Tidal Theory

The Planetesimal Hypothesis

The Clouds of Magellan

John Herschel (17921871)

Drawings by the Earl of Rosse

The Crab Nebula, M1

The Earl of Rosses drawing of a spiral nebula

M51, a spiral nebula

The spiral nebula M81

Sir William Huggins (18241910)

Photographs of stellar spectra

The 36-inch Crossley reflector of the Lick Observatory

A late-nineteenth-century concept of our galaxy

Our galaxy as a spiral nebula

Schematic diagram of a pulsating star

Schematic diagram of an eclipsing variable

Globular star clusters in Sagittarius

The 60-inch reflector of the Mount Wilson Observatory

The current view of our galaxy

The 100-inch telescope of the Mount Wilson Observatory

Variable stars in the Andromeda Nebula

Light variations of Cepheid variables

Nebular types

The Hubble Tuning Fork

A barred spiral, N.G.C. 1300

Wide-angle photograph of the Milky Way, Southern Hemisphere

Edge-on view of spiral galaxy N.G.C. 4565

The Hertzsprung-Russell diagrams of two galactic clusters at different distances

The distribution of globular clusters and galactic clusters

Resolution of an elliptical galaxy, N.G.C. 205

Hertzsprung-Russell diagrams for the two populations

The spiral galaxy M104

The 200-inch Hale telescope, Mount Palomar

The 120-inch telescope of the Lick Observatory

Motions of stars near the sun

Planetary orbits

Schematic representation of the galactic rotation near the sun

Schematic diagram of a spiral galaxy

Negative photographs of two spiral galaxies

Tracing the spiral pattern of the Andromeda Nebula, M31

Spiral pattern of our galaxy

The nuclear jet in M87

An exploding galaxy, M82

A source of radio signals, N.G.C. 1316

The peculiar barred spiral N.G.C. 2685

An explosion? N.G.C. 1275

Four quasars

Dust clouds emerging from the nucleus of M31

For two thousand years, some have known the earth to be round. But only for twenty years have we known the detailed shape of our galaxythe spatial implications of that diffuse band of light we call the Milky Way. This book retraces the trail of ingenious arguments by which astronomers have interpreted the sky and built a picture of the galaxy in which we spin.

On a clear, moonless night in midwinter or midsummer, a plume of starlight rises motionless behind the scattering of constellations. To our eyes, the Milky Way is colorless, but we are deceived by the faintness of the light. If our eyes were more sensitive we would see a splendid display of colors: the blue and red of Orions stars, the deep yellow of Arcturus, the silver of Spica, and the sunlight yellow of Castor and Pollux, glowing wisps of red and pale blue, an occasional gap of dull red in the banks of faint stars.

The Milky Way is our island universeour galaxyand its shape had been outlined by inspired guesswork before 1800, but only within the past two decades have the arguments been made convincing and quantitative. New tools were required at each step, and many tools relied on new concepts, not merely new techniques.

Yet, even lacking quantitative tools, astronomers might have made substantial progress much earlier if it had not been for one disastrous fact, overlooked until 1930. Interstellar space is filled with obscuring dust that weakens starlight, falsifies estimates of distance, and totally blocks the visible light of vast portions of the Milky Way.

The recognition that our Milky Way is a spiral galaxy depended heavily on irrational elements of mans nature: his quest for divine revelation in the sky; his ability to unbridle his imagination and face ridicule from those he most respected; his stubborn insistence that for some problems a wrong answer is better than none; his willingness to hold two mutually contradictory ideas in his head and work with them both; his faith that theories should be esthetic; his preoccupation with the problem of his own identity.

It is just this appearance of irrationality that makes the work of astronomers so fascinating today and that provided the peaks of scientific excitement in the past. The discoveries of the great astronomers were no more inevitable in their time than the paintings of Rembrandt were in his. What they wrote, what they sensed in themselves, stood at the tip of their perceptions.