The American astronomer George Ellery Hale (1868-1938) designed and built three great observatories, invented the spectroheliograph, and discovered magnetic fields in sunspots.

George Ellery Hale was born on June 29, 1868, in Chicago, Illinois, the eldest surviving son of William Ellery Hale and Mary Scranton Browne. His father, a wealthy elevator manufacturer, instilled in Hale from an early age a love for tools and machinery and a deep interest in public affairs. Armed with a box of tools and small lathe for turning metal, Hale transformed his bedroom into a laboratory and later built with his own hands a workshop in the yard.

Hale's mother, a graduate of the Hartford Female Seminary in Hartford, Connecticut, cultivated his literary side, reading aloud the Iliad and the Odyssey and stocking the shelves of his personal library with books ranging from the unabridged Robinson Crusoe and Don Quixote in translation to Grimm's Fairy Tales and the poetry of Shelley and Keats. In biographical notes written in 1933 Hale spoke fondly of these and other classics that "helped greatly to arouse my imagination and prepare me for scientific research."

Early Interest in Astronomy

Hale attended the Oakland Public School and later the Allen Academy, taking also a shop course at the Chicago Manual Training School. But what mattered most to Hale were the studies he worked on at home. Astronomy headed the list. He first built a small telescope, then a spectroscope. Attached to the telescope, now a 4-inch Clark refractor purchased for him by his father, the homemade instrument allowed Hale to observe the solar spectrum. In 1884 he photographed a spectrum using a small commercial spectrometer. To measure more accurately the wavelengths of the dark Fraunhofer lines in the solar spectrum, Hale added a one-inch plane grating to the single prism spectrometer.

Reading everything he could find on spectra during these years, Hale bought Norman Lockyer's Studies in Spectrum Analysis. Inspired, he began laboratory observations of spectra and compared them with those of the sun's spectrum. Out of that work was born Hale's lifelong interest in the physical properties of the sun and stars. In explaining why classical astronomy with its emphasis on determining the positions, distances, and motions of celestial bodies did not appeal to him even then, Hale later wrote: "I was born an experimentalist, and I was bound to find the way of combining physics and chemistry with astronomy."

His First Observatory

Determined to leave his mark on the young science of astrophysics, Hale entered the Massachusetts Institute of Technology (MIT) in 1886, where he studied chemistry, physics, and mathematics. For astronomy, he turned to Edward C. Pickering, director of the Harvard College Observatory, who took him on as a volunteer assistant. During summer vacations he continued his own solar and stellar research in a specially-equipped spectroscopic laboratory of his own design built for him by his father in 1888 on a lot adjacent to the family home in the Kenwood section of Chicago. This formed the nucleus of the Kenwood Physical Observatory.

At the time the standard method of recording solar prominences consisted of drawings based on visual observation. In his quest to find an adequate method of photographing prominences, Hale invented the spectroheliograph--an instrument for photographing phenomena in the solar atmosphere that would otherwise be invisible. The first tests of his new instrument, made in the winter of 1889-1890 at the Harvard Observatory, demonstrated that the basic principle was right. Then a senior at MIT, he wrote up the work for his thesis and received a B.S. in physics. Hale married Evelina Conklin in June 1890, two days after graduation. Upon their return to Chicago, Hale's father agreed to finance the construction of a 12-inch refractor telescope.

At the Kenwood Observatory, dedicated in 1891, Hale continued his experiments with the spectroheliograph. In examining the spectra of prominences, he observed two bright lines (H and K), which he had determined to be due to calcium, in the ultraviolet region. They proved ideal for photographing prominences, as photographic plates then in use were more sensitive to light in the ultraviolet. Moreover, his photographs of solar spectra showed H and K as bright lines all over the sun. Armed with this information and an improved instrument, Hale photographed these calcium clouds (flocculi) and prominences both at the solar limb and across the disc in 1892 for the first time. The success of this research tool sealed Hale's international reputation as a solar astronomer. Many of his findings appeared in Astronomy and Astrophysics, the forerunner of the Astrophysical Journal, a publication founded by Hale in 1895 and still the leading astronomical journal in the field.

Two More Observatories

In 1892 Hale joined the faculty of the new University of Chicago as associate professor of astrophysics and director of the observatory. An accomplished organizer and money-raiser, Hale persuaded streetcar millionaire C. T. Yerkes to provide the university with the largest refractor telescope in the world. Hailed in 1897 for its revolutionary design, the Yerkes Observatory at Williams Bay, Wisconsin, was, as Hale stated, "in reality a large physical laboratory as well as an astronomical establishment." There, with the aid of F. Ellerman and J. A. Parkhurst, Hale carried out a study on the spectra of low-temperature red stars (Secchi's fourth type). Besides continuing his own research on sunspot spectra, he also studied the distribution of calcium flocculi at different levels in the solar atmosphere and found the dark hydrogen flocculi using a large spectroheliograph of his own design built for the 40-inch telescope.

Hale lived by his own motto, "Make no small plans." He founded the Mount Wilson Observatory in Pasadena, California, in 1904 with funds provided by the Carnegie Institution and served as its director until 1923. In an effort to eliminate mirror distortion and air turbulence, Hale designed and built in 1908 a 60-foot tower telescope with a long vertical spectroheliograph in an underground well. By then he had discovered the low temperature of sunspots, the vortex structure of the dark hydrogen flocculi in the vicinity of sunspots, and the magnetic fields of sunspots. The discovery of hydrogen vortices around sunspots suggested to Hale that the double lines in sunspot spectra, photographed with the 60-foot tower telescope, were not due, as previously believed, to "reversals," but rather to intense magnetic fields (the Zeeman effect).

In 1908 Hale compared his astronomical work with the similar doubling of lines obtained with large electromagnets in the observatory's physical laboratory and demonstrated conclusively for the first time the existence of sunspot magnetic fields. Working later with the 150-foot tower telescope, Hale attempted to measure the general magnetic field of the sun; he also formulated the law of sunspot polarities and discovered the reversal of sunspot polarities in successive 11-year cycles.

A solar astronomer primarily, Hale also built stellar telescopes: a 60-inch reflector installed at Mount Wilson in 1908, and a 100-inch telescope inaugurated in 1917. In 1928 the International Educational Board of the Rockefeller Foundation agreed to finance Hale's $6 million proposal to build a 200-inch telescope on Mount Palomar (dedicated in 1948, it bears his name).

A Leader in the Science Community

A scientist bursting with educational, architectural, and civic ideas, Hale was elected to the National Academy of Sciences in 1902 and promptly set about to reform it. He created (and served as first chairman) the National Research Council, the operating arm of the academy, in 1916; aided in establishing a fellowship program in 1919; and raised the endowment for the council and the construction in 1924 of a permanent building for the academy in Washington, D.C. Back in Pasadena, he joined the board of trustees of Throop Polytechnic Institute in 1906 and played a major role in transforming it into the California Institute of Technology, a distinguished school of research and teaching in science and engineering. He influenced the creation of the Henry E. Huntington Library and Art Gallery and worked on the master plan for Pasadena's civic center.

Weakened by a series of nervous breakdowns, Hale resigned as director of the observatory in 1923 and built a small solar laboratory in Pasadena, where he continued to do research on the sun. Honors received during his life-time include the Royal Astronomical Society medal in 1904 and the Copley medal of the Royal Society in 1932 and election to the Accademia dei Lincei and the Royal Society of London, as well as membership in many scientific societies in the United States and abroad. He entered Las Encinas sanitarium in Pasadena following a stroke and died there of heart trouble on February 21, 1938.

Further Reading

• Novelist Theodore Dreiser wrote Hale into his novel about Charles Yerkes, The Titan (1914). A first-hand account of Hale's work in California appears in Ten Years' Work of a Mountain Observatory (1915). The only full-length biography of Hale is Helen Wright, Explorer of the Universe (1966). Walter A. Adams, who succeeded Hale as director of the Mount Wilson Observatory, leaned heavily on Hale's unpublished autobiographical notes in the biographical introduction he prepared for the NAS Biog. Mem. (1940). Hale published six books and over 450 articles, all of which are chronologically listed in Adams' bibliography. Hale's work in astronomy and in developing scientific institutions is vividly revealed in pictures, documents, and essays in Helen Wright, Joan N. Warnow, and Charles Weiner (editors), The Legacy of George Ellery Hale (1972). Good background material is in Owen Gingerich (editor), Astrophysics and Twentieth-Century Astronomy to 1950: Part A (1984) and in Daniel Kevles, The Physicists (1978).
• Osterbrock, Donald E., Pauper & Prince: Ritchey, Hale & big American telescopes, Tuscon: University of Arizona Press, 1993.
• Wright, Helen, Explorer of the universe: a biography of George Ellery Hale, Woodbury, NY: American Institute of Physics, 1994.