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Henrietta Swan Leavitt
Henrietta Swan Leavitt, (1868 - 1921) was the daughter of a Congregational Church minister. She graduated, from what was to be later called Radcliffe College, in 1892 with the equivalent of a Harvard Bachelor of Arts degree. In 1895 she became a volunteer assistant at the Harvard Observatory.
She joined the permanent staff there in 1902. Because of her previous volunteer work she was employed at higher than the average wage. She was engaged to measure the brightnesses of stars by the new technology of photographic photometry.
She devised new methods of analysis & so extended the scale of star brightnesses down to the 21st magnitude. Her system remained in general use until the new photo-electrical technology provided greater accuracy. She discovered 4 novae and around 2,400 variable brightness stars (more than half of those known up to 1930).
She measured the period of regularly varying stars by comparing intensities at different times. Leavitt was astonished by the number of variable stars she discovered. In 1908, she published a paper on “1,777 Variables in the Magellanic Clouds”.
She found many of a type of variable stars, called “Cepheids” (after Delta Cephei in the constellation Cepheus) & in 1912 she plotted a graph of data from 25 Cepheids in the Small Magellanic Cloud. She discovered from the graph that the absolute magnitude of these Cepheid variable stars was given by the period of their variation in brightness. It meant that if two Cepheid stars have the same period and one is dimmer, then the dimmer one is farther away.
In 1913, Ejnar Hertzsprung used a parallax method to determine the distances to a number of Cepheids in the Milky Way. Hertzsprung also devised a way (with a small hiccup) of measuring the distance to any Cepheid. This provided what Astronomers often call a “standard candle”. Edwin Hubble used Leavitt’s relationship & found many Cepheid stars were beyond the Milky Way. He then realised that there were other galaxies beyond ours & suddenly the Universe was much bigger than anyone had realised.
Leavitt became head of stellar photometry at the Harvard College Observatory in 1921, but died of stomach cancer the same year, age 53. Magnus Gösta Mittag-Leffler of the Swedish Academy of Sciences tried to nominate her for the 1926 Nobel Prize in physics, but discovered that she was no longer alive. Nobel Prizes are not awarded posthumously.
Henrietta Swan Leavitt, (1868 - 1921) was the daughter of a Congregational Church minister. She graduated, from what was to be later called Radcliffe College, in 1892 with the equivalent of a Harvard Bachelor of Arts degree. In 1895 she became a volunteer assistant at the Harvard Observatory.
She joined the permanent staff there in 1902. Because of her previous volunteer work she was employed at higher than the average wage. She was engaged to measure the brightnesses of stars by the new technology of photographic photometry.
She devised new methods of analysis & so extended the scale of star brightnesses down to the 21st magnitude. Her system remained in general use until the new photo-electrical technology provided greater accuracy. She discovered 4 novae and around 2,400 variable brightness stars (more than half of those known up to 1930).
She measured the period of regularly varying stars by comparing intensities at different times. Leavitt was astonished by the number of variable stars she discovered. In 1908, she published a paper on “1,777 Variables in the Magellanic Clouds”.
She found many of a type of variable stars, called “Cepheids” (after Delta Cephei in the constellation Cepheus) & in 1912 she plotted a graph of data from 25 Cepheids in the Small Magellanic Cloud. She discovered from the graph that the absolute magnitude of these Cepheid variable stars was given by the period of their variation in brightness. It meant that if two Cepheid stars have the same period and one is dimmer, then the dimmer one is farther away.
In 1913, Ejnar Hertzsprung used a parallax method to determine the distances to a number of Cepheids in the Milky Way. Hertzsprung also devised a way (with a small hiccup) of measuring the distance to any Cepheid. This provided what Astronomers often call a “standard candle”. Edwin Hubble used Leavitt’s relationship & found many Cepheid stars were beyond the Milky Way. He then realised that there were other galaxies beyond ours & suddenly the Universe was much bigger than anyone had realised.
Leavitt became head of stellar photometry at the Harvard College Observatory in 1921, but died of stomach cancer the same year, age 53. Magnus Gösta Mittag-Leffler of the Swedish Academy of Sciences tried to nominate her for the 1926 Nobel Prize in physics, but discovered that she was no longer alive. Nobel Prizes are not awarded posthumously.