George Ellery Hale

Solar Astronomer

• Born: June 29, 1868
• Birthplace: Chicago, Illinois
• Died: February 21, 1938
• Place of death: Pasadena, California

American astronomer

In the early twentieth century, American astronomer George Ellery Hale constructed the world’s largest telescopes. He also discovered solar vortices and learned that sunspots are associated with intense magnetic fields, which proved key to understanding solar activity.

Born: June 29, 1868; Chicago, Illinois

Died: February 21, 1938; Pasadena, California

Primary field: Astronomy

Specialties: Observational astronomy; astrophysics

Early Life

George Ellery Hale was born on June 29, 1868, in Chicago, Illinois, to William Ellery Hale and Mary Scranton Browne. Hale started school at Oakland Public School, but his parents switched him to the private Allen Academy after he had a bout of typhoid fever. At age fourteen, Hale began studying at the Chicago Manual Training School. Many summers were spent at his maternal grandmother’s home in Madison, Connecticut. There, Hale met and began dating Evelina Conklin. In 1886, Hale entered the Massachusetts Institute of Technology (MIT) in Cambridge to study physics. At about the same time, he announced his engagement to Conklin. They were married in June of 1890, shortly after Hale’s graduation.

Hale became interested in science early on, and his father encouraged him. His particular interest in astronomy was fostered by a neighbor, an astronomer of double stars named Sherburne W. Burnham. Burnham showed Hale a spectrum of the sun, which sparked in Hale a lifelong interest in solar activity. In 1884, at the age of sixteen, Hale used a prism spectroscope and telescope purchased by his father to photograph the sun’s spectrum.

As an undergraduate at MIT, Hale focused his research on the sun, specifically solar spectroscopy, the analysis of the sun’s light. While at MIT, he invented the spectroheliograph, an instrument that could image the sun using only one wavelength of light, the hydrogen alpha line. The spectroheliograph enables astronomers to study the sun’s chromosphere layer and to photograph solar prominences.

Life’s Work

In 1891, Hale established a small private observatory near Chicago named the Kenwood Observatory, where he continued his studies. In 1892, he was hired by the University of Chicago as an associate professor of astrophysics; he was the first person to officially hold the title of astrophysicist. Shortly after being hired at Chicago, Hale learned of two large lens blanks (unfinished lenses) produced by renowned telescope maker Alvan Clark. He immediately began working to secure funding for the University of Chicago to build an observatory with the largest refracting telescope ever constructed. Together with university president William Harper, Hale managed to persuade the wealthy streetcar industrialist Charles Yerkes to finance construction of an observatory for the university near Williams Bay, Wisconsin.

Hale commissioned the Alvan Clark & Sons optics company to grind the lenses for a refracting telescope forty inches in diameter as the centerpiece for the observatory. After several cost overruns, which required that Hale persuade Yerkes to donate more money, the Yerkes Observatory opened in 1897.

In addition to establishing the Yerkes Observatory, Hale, together with James Edward Keeler, founded the Astrophysical Journal in 1894, which would become a premier astronomical publication. In 1899, Hale founded the first professional organization for American astronomers. The organization, called the American Astronomical and Astrophysical Society, later changed its name to the American Astronomical Society.

Soon after the completion of the Yerkes Telescope, Hale wanted to build an even larger telescope. He realized that the Yerkes refractor was at the limit of how large lenses could be made for refracting telescopes (telescopes that generate images via light passing through lenses). Larger telescopes would have to be reflecting telescopes (those that make images from light reflecting across an arrangement of mirrors). Hale also decided that the ideal site for a new, larger telescope would be on top of a mountain, where clear air and minimal light pollution would facilitate observations. Hale traveled to southern California to find a site for this new telescope.

Wilson’s Peak (now Mount Wilson), near Pasadena, California, was chosen as the site. Hale set up a small, five-inch solar telescope on the mountain to establish a foothold for an observatory there. In order to focus on the new observatory, Hale resigned from the University of Chicago in 1904. That same year, he received a grant from the Carnegie Institution of Washington to establish the Mount Wilson Observatory. The grant allowed Hale to begin work on a telescope with a sixty-inch mirror. In the meantime, Hale placed a twenty-four-inch solar telescope, called the Snow Telescope, on Mount Wilson. In 1905, he used this telescope to photograph for the first time the spectrum of a sunspot. Once completed, Hale’s sixty-inch telescope, the largest in the world at that time, began operation in 1908.

By 1912, Hale had completed construction of two towers for solar telescopes, and in using them discovered that sunspots are associated with extremely intense magnetic fields. He also discovered solar vortices—energy masses that move in a whirling motion—and realized that magnetic activity cycles are caused by these vortices.

As the sixty-inch telescope was under construction, Hale wanted to build an even larger telescope. He secured funding from John D. Hooker, a wealthy California businessman, for the purchase of a mirror blank that measured one hundred inches in diameter. Hale also convinced Andrew Carnegie to provide another grant to figure the mirror and to construct the telescope. The one-hundred-inch telescope, named the Hooker Telescope, was completed in 1917, and it remained the world’s largest telescope for the next three decades. Early twentieth-century researchers made important astronomical discoveries while using the Hooker Telescope.

At the start of World War I, Hale believed the United States would eventually join the war. He also believed that the advantage of technological superiority would win the war. In 1916, Hale helped to establish the National Research Council, a group organized by the National Academy of Sciences. The council, with Hale as its first president, organized the war efforts of the nation’s scientists.

After the war, Hale had several episodes of severe depression. He had to limit himself to a few hours of work per day and eventually retired as director of the Mount Wilson Observatory in 1923. He then retreated to his private solar observatory in Pasadena, where he worked in isolation. Hale did not completely remove himself from the astronomical community, however. In 1928, he announced plans for what would become the largest telescope in the world: a reflector with a diameter of two hundred inches. He secured initial funding from the Rockefeller Foundation to site the instrument atop Mount Palomar in California, at what would become the Palomar Observatory.

By 1932, Hale’s depression had worsened, and he spent the next six years in and out of sanitaria (mental hospitals). He died in Pasadena on February 21, 1938.

Impact

World War II delayed construction of the telescope at Palomar, but when it was finally completed in 1948, it was named the Hale Telescope. The Hale Telescope was the world’s largest accurate reflecting telescope for forty-five years. The Yerkes refractor remains the last and largest refracting telescope ever constructed.

Hale’s drive to build new and bigger telescopes was foundational in making the United States a major contender in the science of astronomy. His telescopes and observatories are still in use. One of the first observations made with the Hale Telescope led to a doubling of the estimated distance scale between the Milky Way and the Andromeda galaxies, from one million light-years to two million light-years. In addition to helping establish diagrams of the distribution of neighboring galaxies, the Hale Telescope has helped astronomers conduct spectroscopic studies of galaxies, which are analyses of the light given off by them. These studies allow astronomers to determine whether galaxies are receding from or moving toward the Milky Way and how fast they are doing so. Observations made with the Hale Telescope have suggested that the universe is expanding, lending support to the Big Bang theory.

Hale’s observations of the sun, particularly his discoveries of solar vortices and that magnetic activity is associated with sunspots, set the stage for later solar astronomers seeking to understand the sun’s composition. The instruments and techniques that Hale developed for solar astronomy, including his spectroheliograph, have continued to be used by astronomers. In addition, his Astrophysical Journal has become a prominent publication in the field, and the American Astronomical Society remains the major professional organization for American astronomers.

Bibliography

Glass, Ian S. Revolutionaries of the Cosmos: The Astro-Physicists. New York: Oxford UP, 2008. Print. Biographies of some of the most important astronomers, with a chapter devoted to Hale.

Osterbrock, Donald E. Pauper and Prince: Ritchey, Hale, and Big American Telescopes. Tucson: U of Arizona P, 1993. Print. A chronicle of Hale’s observatory-building activities.

---. Yerkes Observatory, 1892–1950: The Birth, Near Death, and Resurrection of a Scientific Research Institution. Chicago: U of Chicago P, 1999. Print. The story of Hale’s first major observatory.

Sandage, Allan. “The Mount Wilson Observatory.” Centennial History of the Carnegie Institution of Washington. Vol 1. New York: Cambridge UP, 2004. Print. A look at the Wilson Observatory, funded in part by the Carnegie Institution, and its first one hundred years of operation.

Tenn, Joseph S. “George Ellery Hale: The Thirteenth Bruce Medalist.” Mercury 21.3 (1992): 94–97. Print. A brief biography of Hale and his life’s work.