George Ellery Hale and the Magnetic Fields in Sunspots

George Ellery HaleOn 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. After graduating from High School, Hale studied chemistry, physics, and astronomy at Allen Academy. Hale continued his education at MIT, at the Harvard College Observatory,  and at Berlin.

George Ellery Hale became known for inventing the spectroheliograph, with which he made his discovery of solar vortices. In 1908, he used the Zeeman effect with a modified spectroheliograph to establish that sunspots were magnetic. Further work on the subject emonstrated 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.

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.

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