Henrietta Leavitt (1868-1921) was a barrier breaking astronomer whose work on Cepheid stars led to a complete re-evaluation of the size of the known universe.
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Hello! From Wonder Media Network, I’m Jenny Kaplan and this is Encyclopedia Womannica.
Today’s STEMinist was a barrier breaking astronomer whose work on Cepheid stars led to a complete reevaluation of the size of the known universe. Her work was instrumental to the development of the fields of astronomy, cosmology, and astrophysics. Let’s talk about the extraordinary Henrietta Leavitt.
Henrietta Swan Leavitt was born on July 4th, 1868 in Lancaster, Massachusetts to George and Henrietta Leavitt. She was the first of their seven children.
Growing up, Henrietta’s family was fairly well off. Her father, George, worked as a minister in the Congregational Church. The downside of George’s job was that the family had to move whenever he changed congregations.
When Henrietta was in her teens, the family moved to Cleveland, Ohio. After graduating from high school in 1885, Henrietta enrolled in a one year college preparatory course at Oberlin College, followed by two years as an undergraduate there. At the time, Henrietta was studying music.
Following her sophomore year at Oberlin, Henrietta and her family moved back east to Cambridge, Massachusetts, home of Harvard University. Henrietta was desperate to enroll at Harvard, but the university didn’t accept women at the time. Instead she enrolled at what was then known as the “Harvard Annex,” an educational establishment for women that would eventually change its name to Radcliffe College. For two years, Henrietta studied math and astronomy, before graduating in 1892.
Following graduation, Henrietta took a job as a volunteer research assistant at the Harvard College Observatory. Though her parents had to support her financially during her time there, she was able to build up credits towards an advanced degree in astronomy, and she found great satisfaction in the work.
At the observatory, Henrietta was part of a large project attempting to catalog the brightness, position, and color of all observable stars in the universe, which at the time was believed to consist of just the Milky Way. Henrietta was tasked with analyzing photographs in order to determine the necessary star data. She was asked to pay particular attention to any star whose brightness varied over time, and to record how long the cycle of bright to dim to bright again took, otherwise known as the period of variation.
At the beginning of 1896, Henrietta left Harvard to spend some time in Europe. She was having issues with both her sight and hearing, and her doctors had suggested that a trip abroad might help. Upon her return to the United States two years later, Henrietta moved to Wisconsin, where her father had just taken a job at a new congregation. Henrietta managed to find a job for herself as an assistant at the local college.
In 1902, after five years in Wisconsin, Henrietta contacted Edward Pickering, the director of the Harvard College Observatory, with a request to have her old lab notebooks sent to her in Wisconsin. She wanted to complete the report on stars she had started so many years before. She also asked Pickering if he knew of any observatory jobs located in warm weather, since it was better for her health.
Pickering was unaware of any job openings in the tropics, but he was so impressed with Henrietta’s previous work that he offered her a paid full-time job at the Harvard College Observatory as a computer. Computers, as they were called at the time, were people who did all of the calculations and data analysis by hand. This also gave Henrietta the opportunity to finish up the work on the star catalogue.
In 1908, Henrietta published her first academic paper summarizing her work on the star catalogue. The paper focused on the existence of an extraordinarily large number of stars with variable brightness located in the Magellanic Clouds. Most importantly, she noted that brighter variable stars have longer periods, meaning it takes longer for them to go from dim to bright to dim again.
For four years, Henrietta continued the time-consuming work of analyzing variable stars. She discovered that there was one type of variable star, called a Cepheid star, that seemed to pulse at a rate directly related to the star’s actual brightness. Since there is a very clear and precise relationship between brightness and distance, Henrietta realized that one could potentially use a Cepheid star’s variability to calculate the distance from that star to earth. This was a major revelation.
In 1912, Henrietta published a paper about her breakthrough. It was extraordinarily well-received by the scientific community, and astronomers around the world began working to utilize Henrietta’s discovery. Just a year later, a European astronomer was able to determine the distance of a number of Cepheid stars from earth, which laid the groundwork for a method of determining the distance of any Cepheid. These Cepheids, with known brightness to distance ratios, became known in astronomy as standard candles.
Utilizing Henrietta’s work, Edwin Hubble then calibrated how to measure the distance to Cepheids located even farther away. To his astonishment, he discovered that many of these Cepheids were so far away that they were actually beyond the Milky Way. These stars were in other galaxies, meaning that the universe was much bigger and filled with much more than humanity had imagined up to that point.
In 1921, having truly made a name for herself in her field, Henrietta was named the head of the stellar photometry department at Harvard College Observatory. Sadly, she passed away before she could start her new job.
Henrietta died on December 12, 1921 in Cambridge, Massachusetts from stomach cancer. She was just 53 years old.
Due to the importance of Henrietta’s work in the development of the fields of cosmology, astronomy, and astrophysics, Magnus Gösta Mittag-Leffler of the Swedish Academy of Sciences tried to nominate her for the 1926 Nobel Prize in physics. His attempt failed, however, when he learned she had already died. Nobel Prizes are not awarded posthumously.
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