George Ellery Hale – Large Telescopes and the Spectroheliograph

George Ellery Hale

George Ellery Hale (1806-1861)

On June 29, 1868, American solar astronomer George Ellery Hale was born. He is best known for his discovery of magnetic fields in sunspots, and as the leader or key figure in the planning or construction of several world-leading telescopes, including the 200-inch Hale reflecting telescope at Palomar Observatory.

George Ellery Hale was the oldest of three children  and it is believed that he was highly supported by his parents in developing his curiosity and mind, and receive a good education in poetry and literature. It is further assumed that he was interested in optics early, and even working in a home laboratory with the support of his parents. Around the age of 16, Hale built his first telescope which was later replaced by a second-hand Clark refractor. The young scientist began photographing the night skies, observing a partial eclipse of the sun, and drawing sun-spots.

Next to his early scientific achievements, George Ellery Hale was also an avid reader and especially  enthusiastic about Jules Verne [4] After graduating from High School, Hale studied chemistry, physics, and astronomy at Allen Academy. Hale continued his education a tMassachusetts Institute of Technology (MIT), was at Harvard College Observatory in 1889/90 and in Berlin in 1893/94. In 1890 he ran his own observatory (Kenwood Astrophysical Observatory) on the family estate in Chicago’s Kenwood district.

At the age of 21, he developed the spectroheliograph as a student at the MIT around 1890 (simultaneously with Henri-Alexandre Deslandres). This instrument was soon used worldwide to study the sun in narrow spectral ranges. In 1908, he used the Zeeman effect with a modified spectroheliograph to establish that sunspots were magnetic. Further work on the subject demonstrated a strong tendency for east-west alignment of magnetic polarities in sunspots, with mirror symmetry across the solar equator, and that the polarity in each hemisphere switched orientation from one sunspot cycle to the next. This systematic property of sunspot magnetic fields is now commonly referred to as the Hale–Nicholson law, or simply Hale’s law.

From 1891 to 1893 he was professor of astrophysics at Beloit College in Beloit (Wisconsin). Hale was appointed to the University of Chicago in 1892, where he was Associate Professor until 1897 and Professor until 1905. Since he heard about a new 40-inch lens in the same year, he decided to build a large observatory. Hale managed to find a rich sponsor from Chicago: Charles Yerkes. In 1897, the huge 102 cm refractor at the new Yerkes Observatory became the largest telescope in the world at the time. It is still the largest optical telescope ever built.

As secretary for foreign relations at the National Academy of Sciences, Hale nominated the German physicist Johannes Stark for the Nobel Prize in Physics in 1914 and 1916 despite the First World War. At Hale’s instigation, the National Research Council was founded in 1916, for which Hale then worked together with Robert Andrews Millikan until 1917. Hale’s goal was to use scientists instead of normal military service according to their qualifications as scientists.

During his career, Hale worked to found a number of significant astronomical observatories, including Yerkes Observatory, Mount Wilson Observatory, Palomar Observatory, and the Hale Solar Laboratory. He hired and encouraged Harlow Shapley and Edwin Hubble toward some of the most significant discoveries of the time. Further, Hale played a central role in developing the California Institute of Technology into a leading research university.

Hale began promoting the construction of a huge telescope mirror in 1927. In 1928 he was able to convince the president of the Rockefeller Foundation of this huge investment in science. The reflecting telescope on Mount Palomar was completed in 1947. With a main mirror of 200 inches (5 meters), it was the largest telescope in the world until 1975. Today it is still the largest telescope with equatorial mount.[5]

Hale suffered from neurological and psychological problems, including insomnia, frequent headaches, and depression. The often-repeated myth of schizophrenia, alleging he claimed to have regular visits from an elf who acted as his advisor, arose from a misunderstanding by one of his biographers. He used to take time off to spend a few months at a sanatorium in Maine. These problems forced him to resign as director of Mount Wilson.

References and Further Reading:

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