MIT's Solar Pioneer
Spying on the sun’s “marvelous beasts”
When George Ellery Hale started at MIT in 1886, he found his textbooks distracting; he barely passed organic chemistry on the way to his bachelor’s degree in physics four years later. Yet he was to become one of the luminaries of solar astronomy, and one of his most important achievements was an invention he created during those undergraduate years.
Something of a loner, Hale was always happiest peering through a telescope. He spent his free time researching astronomy at the Boston Public Library (MIT was then in the nearby Back Bay neighborhood) and volunteering at the Harvard College Observatory under Edward C. Pickering, who had previously taught at MIT. During school breaks, Hale would retreat to his parents’ home in Chicago, where he had set up a solar observatory in the attic. His dedication paid off in his last year at MIT, when he constructed the first successful spectroheliograph–an instrument that recorded, on a photographic plate, wavelengths emitted by individual elements present in the sun. The instrument enabled him to produce detailed images of sunspots as well as the loops of relatively cool plasma known as solar prominences. His 1890 senior thesis, “Photography of the Solar Prominences,” reported his revolutionary results. “Nearly all our existing knowledge regarding the … forms and motions of prominences, details in the [sun’s atmosphere], and the structure of the solar surface around sunspots is due to the spectroheliograph or to some adaptation of its principles,” a prominent astronomer would write upon Hale’s death in 1938.
Hale thought about the sun constantly, even while on his honeymoon with Evelina Conklin, whom he married two days after his graduation. The young couple made a stop at Lick Observatory, near San Jose, CA, where a fellow astronomer entertained Evelina while Hale stargazed. Back in Chicago, with his father’s support, Hale expanded his home laboratory into the Kenwood Astrophysical Observatory. In 1892, at age 24, he began teaching astrophysics at the University of Chicago and donated the Kenwood Observatory to the school. The same year, Hale convinced streetcar magnate Charles T. Yerkes to fund what would become, for a time, the largest refracting telescope ever used–40 inches across. The Yerkes Observatory was completed in Williams Bay, WI, in 1897.
In 1904, Hale also established the Mt. Wilson Solar Observatory near Pasadena, CA, where he oversaw construction of a 100-inch reflecting telescope, the largest of the time. It would be used by Edwin Hubble and other influential astronomers. And toward the end of his life, Hale created the spectrohelioscope, which made it possible to observe the sun directly instead of photographically. He described the experience in a 1926 letter to his nephew:
“Beyond the air stands the sun, with wild and fantastic beasts roaming over its surface. They are of enormous size, sometimes reaching up to heights of four hundred thousand miles. And they are fearfully hot, made of hydrogen, helium, and calcium, in the form of gas so thin that it is only about a thousandth part as dense as the air you are breathing. Naturally, when you look at the brilliant surface of the sun with a telescope you do not see these beasts, because they are so thin that they don’t cut out any appreciable fraction of the light. But if you had a window through which you could see nothing but things made of hot hydrogen, they would suddenly come into view. I have made such a window, and have been looking through it at these marvelous beasts.”
Hale’s commitment to advancing scientific knowledge went beyond his inventions. He founded the Astrophysical Journal, worked to create the National Research Council, and organized what would later become the International Astronomical Union. He also wrote six books and hundreds of articles and transformed the Throop Polytechnic Institute into the California Institute of Technology, intending to make it an institution comparable to MIT, though broader in scope. In a 1907 Technology Review essay titled “A Plea for the Imaginative Element in Technical Education,” he wrote, “The greatest advances, whether in engineering … or in any other field, arise as mental pictures, at first uncertain as to details, but subsequently clear and distinct, requiring only an application of text-book methods to give them tangible form. It is in the conception of the picture, and not simply in the execution of the project it embodies, that the truly great engineer must excel.” He added, “It would thus seem to be evident that a technological school can by no means afford to underestimate the need of broadening the view and cultivating the imagination of its students.”