Henrietta Swan Essay

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Leavitt’s discovery of the period-luminosity relation for Cepheid variable stars In the early 1900’s Henrietta Leavitt’s extensive research on Cepheid Variable stars enabled her to determine the relationship between the period and luminosity of stars to determine their distance from earth. Variable stars emit lights in different intensities and are also known as “lighthouse stars”. There is a direct relationship these stars have, which has a significant role in establishing the distance from earth, of stars that are in excess of 100 light years away (Mitchell, 1976, 162). This is the relationship between luminosity and the pulsation period of these stars. With luminosity being a measure of brightness and pulsation period being the time taken to complete an illumination cycle. Leavitt’s was always interested in astronomy as a child through the stimulation of her mechanical engineer uncle Erasmus Leavitt (Nix, 1998). An astronomy course in her senior year reawakened Leavitt’s interest in Astronomy, and it is from this point that her career as an astronomer started to take place. In 1895 Leavitt began volunteering at the Harvard College Observatory. She was initially used as a human computer. Given the mundane task of photographing stars and crunching numbers. As she worked, she was also instructed to keep an eye out for variable stars, those that regularly increase and decrease in brightness (Bartusiak, 2009). After leaving the Harvard Observatory it was not until she returned after several years “she noticed that several stars had changed in brightness, as if they were undergoing a slow-motion twinkle” (Bartusiak, 2009). She then began going over old photos from before she left, comparing them to the photos she had more recently taken. It is through these comparisons that Leavitt’s was able to make her astronomical breakthrough. By comparing the data from

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