History and Biography of Astronomers: Herschel, Hale and Leavitt

About the history and biography of astronomers Herschel, Hale, and Leavitt the shift in modern astronomy from planets to stars.

The Astronomers

William Herschel (1738-1822) discovered Uranus almost by accident, which is also the way he became an astronomer. Like his father, Herschel became a musician in the Hannover Guards in Germany. But upon being shot at a few times, and realizing musicians could be mortal, he decided to move to England to follow less martial musical pursuits. While working as a musical director, Herschel developed an interest in astronomy. Then, as now, telescopes were expensive, so he decided to make his own. His sister, Caroline, perhaps the 1st female astronomer, assisted him. Herschel became so proficient at using the telescopes he made that he was able to recognize some fuzzy spots as nebulae, stellar dust clouds. He was also able to identify many double stars.

Herschel was the 1st to attempt to measure distances to stars by scientific means-he compared the stars' brightnesses to their distances. He was off by a factor of 10 times. His other great accomplishment was to be the father of John Herschel, who became an outstanding astronomer.

Until the 20th century astronomers' attention was primarily on the solar system, with less emphasis given to outer space. After 1900, the situation reversed itself. True, astronomers like Gerald Kuiper (1905- ) are still making discoveries--such as the satellites of Uranus and Neptune--but time, money, and instruments are increasingly devoted to the stars.

To examine distant stars, gigantic apparatus is needed. The chief provider of these instruments in the early 20th century was George E. Hale (1868-1938). An ingenious astronomer, he was the inventor of the spectroheliograph--a device that allows pictures of the sun's spectra to be taken. Hale had the ability to get generous contributions for the building of large telescopes. In 1892, he built a 40" telescope, financed by a Chicago streetcar magnate, at the Yerkes Observatory in Wisconsin. In 1904, he established the Mount Wilson Observatory in California, and by 1917 had a 60" and a 100" telescope operating. He was behind the building of the 200" telescope at Mount Palomar, Calif. These large telescopes provided the necessary tools to open up space.

The theory needed to understand the new discoveries was provided by Henrietta Leavitt (1868-1921) and Ejnar Hertzsprung (1873-1967). Leavitt, while studying the Magellanic Clouds, galaxies near our own, recognized some stars that vary in brightness in a very regular way. She was able to calculate the relationship between the star's brightness and the length of its period. If she could measure the length of the star's period, she automatically knew its brightness and had a measure of the star's and the galaxy's distance. Hertzsprung, originally a chemical engineer, determined the relationship between a star's color and brightness to find the star's size. Between the 2 astronomers a means of measuring a star's or galaxy's distance had been devised.

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