Chapter I: Preface

Fourteen years ago, in a book entitled "The Study of Stellar Evolution" (University of Chicago Press, 1908), I attempted to give in untechnical language an account of some modern methods of astrophysical research. This book is now out of print, and the rapid progress of science has left it completely out of date. As I have found no opportunity to prepare a new edition, or to write another book of similar purpose, I have adopted the simpler expedient of contributing occasional articles on recent developments to _Scribner's Magazine_, three of which are included in the present volume.

I am chiefly indebted, for the illustrations, to the Mount Wilson Observatory and the present and former members of its staff whose names appear in the captions. Special thanks are due to Mr. Ferdinand Ellerman, who made all of the photographs of the observatory buildings and instruments, and prepared all material for reproduction. The cut of the original Cavendish apparatus is copied from the _Philosophical Transactions for 1798_ with the kind permission of the Royal Society, and I am also indebted to the Royal Society and to Professor Fowler and Father Cortie for the privilege of reproducing from the _Proceedings_ two illustrations of their spectroscopic results.

G. E. H.

January, 1922.

CONTENTS

CHAPTER
I. THE NEW HEAVENS
II. GIANT STARS
III. COSMIC CRUCIBLES

ILLUSTRATIONS

FIG.
1. The Constellation of Orion (Hubble)
2. The Great Nebula in Orion (Pease)
3. Model by Ellerman of summit of Mount Wilson, showing the observatory
buildings among the trees and bushes
4. The 100-inch Hooker telescope
5. Erecting the polar axis of the 100-inch telescope
6. Lowest section of tube of 100-inch telescope, ready to leave Pasadena
for Mount Wilson
7. Section of a steel girder for dome covering the 100-inch telescope,
on its way up Mount Wilson
8. Erecting the steel building and revolving dome that cover the Hooker
telescope
9. Building and revolving dome, 100 feet in diameter, covering the
100-inch Hooker telescope
10. One-hundred-inch mirror, just silvered, rising out of the
silvering-room in pier before attachment to lower end of telescope
tube. (Seen above)
11. The driving-clock and worm-gear that cause the 100-inch Hooker
telescope to follow the stars
12. Large irregular nebula and star cluster in Sagittarius (Duncan)
13. Faint spiral nebula in the constellation of the Hunting Dogs (Pease)
14. Spiral nebula in Andromeda, seen edge on (Ritchey)
15. Photograph of the moon made on September 15, 1919, with the 100-inch
Hooker telescope (Pease)
16. Photograph of the moon made on September 15, 1919, with the 100-inch
Hooker telescope (Pease)
17. Hubble's Variable Nebula. One of the few nebulæ known to vary in
brightness and form
18. Ring Nebula in Lyra, photographed with the 60-inch (Ritchey) and
100-inch (Duncan) telescopes
19. Gaseous prominence at the sun's limb, 140,000 miles high (Ellerman)
20. The sun, 865,000 miles in diameter, from a direct photograph showing
many sun-spots (Whitney)
21. Great sun-spot group, August 8, 1917 (Whitney)
22. Photograph of the hydrogen atmosphere of the sun (Ellerman)
23. Diagram showing outline of the 100-inch Hooker telescope, and path of
the two pencils of light from a star when under observation with the
20-foot Michelson interferometer
24. Twenty-foot Michelson interferometer for measuring star diameters,
attached to upper end of the skeleton tube of the 100-inch Hooker
telescope
25. The giant Betelgeuse (within the circle), familiar as the conspicuous
red star in the right shoulder of Orion (Hubble)
26. Arcturus (within the white circle), known to the Arabs as the "Lance
Bearer," and to the Chinese as the "Great Horn" or the "Palace of the
Emperors" (Hubble)
27. The giant star Antares (within the white circle), notable for its red
color in the constellation Scorpio, and named by the Greeks "A Rival
of Mars" (Hubble)
28. Diameters of the Sun, Arcturus, Betelgeuse, and Antares compared with
the orbit of Mars
29. Aldebaran, the "leader" (of the Pleiades), was also known to the Arabs
as "The Eye of the Bull," "The Heart of the Bull," and "The Great
Camel" (Hubble)
30. Solar prominences, photographed with the spectroheliograph without an
eclipse (Ellerman)
31. The 150-foot tower telescope of the Mount Wilson Observatory
32. Pasadena Laboratory of the Mount Wilson Observatory
33. Sun-spot vortex in the upper hydrogen atmosphere (Benioff)
34. Splitting of spectrum lines by a magnetic field (Bacock)
35. Electric furnace in the Pasadena Laboratory of the Mount Wilson
Observatory
36. Titanium oxide in red stars
37. Titanium oxide in sun-spots
38. The Cavendish experiment
39. The Trifid Nebula in Sagittarius (Ritchey)
40. Spiral nebula in Ursa Major (Ritchey)
41. Mount San Antonio as seen from Mount Wilson