Remembering astronomer Henrietta Swan Leavitt

On the evening of December 12, 1921, as 53-year-old astronomer Henrietta Swan Leavitt died of cancer, heavy rains fell from the sky over Cambridge, Massachusetts. After nearly 30 years at Harvard College Observatory, Leavitt and his stars, hidden by rain clouds, parted ways. Leavitt lived a short but profoundly life-changing life, during which his accomplishments were not widely recognized. On the centenary of his death, we reflect on his life and his legacy.

Leavitt was born in Massachusetts in 1868 and was one of a small group of women in the United States who were given the opportunity to attend college. She first enrolled at Oberlin College before transferring to Harvard University Women’s School, later named Radcliffe. There she studied art, philosophy, language and mathematics. In her final year, she took an astronomy course at the Harvard College Observatory.

By the end of the 19th century, the number of women with university degrees had increased dramatically, but there were still few professional positions available for women with formal university education and even fewer in the sciences. With a new interest in astronomy and the financial support of her family, Leavitt chose to volunteer as a research assistant at the Harvard College Observatory.

Leavitt works at the Harvard College Observatory. (Image courtesy of American Institute of Physics, Emilio Segrè Visual Archives.)

Edward Pickering, the director of the observatory, assembled a group of women to catalog all the stars captured in Harvard’s collection of photographic plaques. These skilled workers were not licensed to operate telescopes, but they helped analyze data that led to major scientific discoveries. Some of the women in this group, called “computers”, classified the stars according to their colors, luminosity and spectra. Pickering gave Leavitt the task of studying variable stars, a type of star whose brightness varies over time.

Cataloging variable stars was tedious work. Leavitt had to compare pairs of photographs, recorded on glass plates, taken of the same part of the sky on different nights. She painstakingly examined each star – each photographic plate contained thousands of stars – for the slightest change in brightness. Through close observation and careful attention, Leavitt noticed a significant pattern in the appearance of Cepheid stars, a type of variable star whose brightness varies with a regular “period” (the time it takes for a star to switch from one level of brightness to another). .

Leavitt observed that Cepheid stars with long half-lives were relatively brighter than Cepheid stars with short half-lives. She determined that there was a direct relationship between a star’s gradation period and the star’s intrinsic luminosity. This meant that if an astronomer could measure the period of any Cepheid star, he could infer its intrinsic luminosity. Once a star’s intrinsic brightness is known, astronomers can calculate how far away the star is by knowing how much light decreases as it moves. This was quickly recognized as a valuable new tool for measuring distances to this class of variable stars, even when they are located far from Earth.

Leavitt excelled in examining photographic plates. She was good at spotting variable stars in every photograph she analyzed and was adept at determining their change in brightness. However, she was unable to engage in this work on a regular basis, largely due to ongoing health issues, which she suffered for most of her life. At 17, Leavitt began to suffer from hearing loss, which continued to decline throughout her life. She visited frequently with her parents in Wisconsin where she stayed while recovering from various illnesses. Because Pickering valued her skills so much, he gave her extended leave and made arrangements for her to work remotely.

Although Pickering recognized and rewarded Leavitt for her skills and abilities – she was ultimately paid 30 cents an hour, five cents more than most computers – he limited the type of work she could tackle . Few computer women were allowed to work independently on any questions they might have about the universe. Although Leavitt wanted to continue her work to understand Cepheid’s variables, as a computer she had little control over her work and was given other tasks. She was not allowed to resume theoretical work that would have allowed her discovery of the unique property of Cepheid stars to be put into practice. This activity was reserved for male astronomers who followed it. She passed away before realizing the full impact of her discovery.

One hundred years after his death, historians, librarians, archivists, authors and artists recognize and count with the devaluation and erasure of Leavitt’s contributions to astronomy. Thanks to the work of the Harvard-Smithsonian Center for Astrophysics’ PHaEDRA project, more people have access to Leavitt’s work than ever before. Authors including Dava Sobel researched and told Leavitt’s story using these resources, including his astronomy notebooks and glass plates.

Leavitt’s engagement with glass plaques caught the artist’s attention Anna von mertens, Smithsonian Artist Researcher 2021, which explores astronomical themes in his multimedia work. From 2018 to 2019, the Harvard Radcliffe Institute exhibited Measure, a collection of von Merten artwork inspired by Leavitt’s life and legacy. The artist reflects Leavitt’s practice of keen observation, keen attention and comparison in his own artistic practice of quilting.

The stars fading on the morning of Henrietta Leavitt’s birth, July 4, 1868, Lancaster, Massachusetts; The stars return to view on the evening of Henrietta Leavitt’s death, December 12, 1921, in Cambridge, Massachusetts. (From the 2018 exhibition Measure, at the Johnson-Kulukundis Family Gallery, Radcliffe Institute for Advanced Study, Harvard University. Hand-sewn cotton, each panel 100 “x 54”. Photo by Steward Clements)

His two-part quilt (or diptych) depicts stars seen on the morning of Leavitt’s birth in Lancaster, Massachusetts, and the night of his death in Cambridge, Massachusetts. Between these bookends hangs a life that little is known or remembered. “Historically, quilts have been objects that carry stories through time,” von Mertens explained in his introduction to the Measure exhibition catalog. “They connect generations and allow silent voices to be heard. Her quilt continues Leavitt’s legacy.

Remembrance is also a central theme in the work of Dr. Aura Satz, whose 2014 works on Leavitt are in the collection of the Smithsonian’s National Portrait Gallery. In the print entitled Leavitt crater, Satz overlaid Leavitt’s portrait with a photograph of a lunar crater named in his honor. She criticizes this commemoration of Leavitt on the topography of the Moon. “The idea that women’s names are associated with imperceptible craters on the moon,” Satz explained in a 2016 interview with Art Forum, “seemed an apt metaphor for women having a moment of slight visibility and then wandering off into the far distance of the story.”

Leavitt crater by Aura Satz, 2014 (National Portrait Gallery, Smithsonian Institution)

Leavitt’s legacy shines brighter today than during his lifetime. To learn more about Leavitt and she Science, and join the museum in our effort to bring Leavitt’s contributions to the forefront, explore these collections from the Smithsonian Learning Lab.

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