The “Harvard Computers”: Henrietta Swan Leavitt’s Expanding Universe
The “Harvard Computers”: Henrietta Swan Leavitt’s Expanding Universe
The "Harvard Computers," as they were called, were a team of brilliant women who observed, charted, and processed astronomical data at the Harvard Observatory in Cambridge, Massachusetts, between 1877 and 1919. Edward Charles Pickering directed this hand-selected team until his death in 1919, and then Annie Jump Cannon became its director.
From the beginning, the women were challenged to make sense of star patterns by designing a scheme for sorting them into categories. Annie Jump Cannon's success in her area of focus produced a stellar classification system that is still in use today. Antonia Maury discerned in the spectra a way to assess the relative sizes of stars, and Henrietta Leavitt showed how the cyclic changes of certain pulsing, or variable stars (called Cepheids) could serve as distance markers in space. All of the women made significant contributions to astronomy, much of which they published in research articles.
Henrietta was born in Lancaster, Massachusetts to Rev. George Roswell Leavitt, pastor of the Congregationalist Church, and his wife, Henrietta Swan Kendrick. Her father was a descendant of Puritans who had settled in the Massachusetts Bay Colony in the late 1600s. Henrietta came to know Christ as a young girl and remained deeply devoted to God and her church throughout her lifetime. As a mid-teen, Henrietta attended Oberlin College, and then transferred to Harvard's new college for women, later named Radcliffe College, in a time when few women had the opportunity to study at this level.
She was a gifted student, learning Latin, classical Greek, fine arts, philosophy, analytical geometry, and calculus, excelling in all areas of mathematics. In her fourth year, she took a course in astronomy and became captivated with the stars. Following graduation in 1892, Henrietta took some time to travel abroad and teach. She came home a year later and began voluntarily working at the Harvard Observatory. She was hired in 1902 by Edward Pickering, who gave her the job of measuring and cataloguing the brightness of stars as they appeared in the observatory's photographic glass plate collection, particularly those in the Small and Large Magellanic galaxies.
Henrietta did her work well, despite an illness that left her profoundly deaf. She was hard-working, serious-minded, little given to frivolous pursuits and selflessly devoted to her family, her church, and her career. Along the way, Henrietta identified 1,777 variable stars, or Cepheids. In 1908 she published her results in the Annals of the Astronomical Observatory of Harvard College, noting that the brighter variables had the longer period.
Using photometry, Henrietta analyzed the Great Nebula in Orion. Her work was then expanded to study the variables of the entire sky with Annie Jump Cannon and Evelyn Leland. She compared stars in different exposures and discovered that, since all those stars were approximately the same distance from Earth, their absolute brightness must allow for the use of Cepheid variables as a "standard candle" for determining cosmic distances. That, in turn, led directly to the modern understanding of the true size of the universe.
Leavitt also developed, and continued to refine, the Harvard Standard for photographic measurements, a logarithmic scale that orders stars by brightness over 17 magnitudes. She initially analyzed 299 plates from 13 telescopes to construct her scale, which was accepted by the International Committee of Photographic Magnitudes in 1913. That year, Leavitt discovered T Pyxidis, a recurrent nova in Pyxis, and one of the most frequent recurrent novae in the sky with eruptions observed in 1890, 1902, 1920, 1944, 1967, and 2011.
In 1921, when Harlow Shapley became director of the observatory, Henrietta was promoted to head of stellar photometry. By the end of that year, however, she died of stomach cancer at fifty-three years old, and was buried in the family plot in the Cambridge Cemetery.
Henrietta's research allowed future scientists to make further discoveries in space. Her friend, astronomer Edwin Hubble, used Leavitt's method to calculate the distance of the nearest galaxy to the earth, the Andromeda Galaxy. This led to the realization that there are even more galaxies than previously thought, and provided evidence that "spiral nebulae" are independent galaxies located far outside of the Milky way.
Thus, Leavitt's discovery would forever change humanity's picture of the universe, as it prompted Harlow Shapley to move the Sun from the center of the galaxy in the "Great Debate" and Edward Hubble to move the Milky Way galaxy from the center of the universe. Henrietta's discovery of a way to accurately measure distances on an inter-galactic scale paved the way for modern astronomy's understanding of the structure and scale of the universe. Hubble often said that Leavitt deserved the Nobel Prize for her work.
At the time of her death, Henrietta was unaware that her life's research would lay the foundation for the next level of space exploration. Although quiet and studious, she was known as someone who delighted in the Creator who knows every star by name, every intimate detail of His marvelous Creation. Her devotion was to God alone. She was a peaceweaver, a pathfinder, a star-charter, and all of her life pointed to Him.
-Karen O'Dell Bullock
From the beginning, the women were challenged to make sense of star patterns by designing a scheme for sorting them into categories. Annie Jump Cannon's success in her area of focus produced a stellar classification system that is still in use today. Antonia Maury discerned in the spectra a way to assess the relative sizes of stars, and Henrietta Leavitt showed how the cyclic changes of certain pulsing, or variable stars (called Cepheids) could serve as distance markers in space. All of the women made significant contributions to astronomy, much of which they published in research articles.
Henrietta was born in Lancaster, Massachusetts to Rev. George Roswell Leavitt, pastor of the Congregationalist Church, and his wife, Henrietta Swan Kendrick. Her father was a descendant of Puritans who had settled in the Massachusetts Bay Colony in the late 1600s. Henrietta came to know Christ as a young girl and remained deeply devoted to God and her church throughout her lifetime. As a mid-teen, Henrietta attended Oberlin College, and then transferred to Harvard's new college for women, later named Radcliffe College, in a time when few women had the opportunity to study at this level.
She was a gifted student, learning Latin, classical Greek, fine arts, philosophy, analytical geometry, and calculus, excelling in all areas of mathematics. In her fourth year, she took a course in astronomy and became captivated with the stars. Following graduation in 1892, Henrietta took some time to travel abroad and teach. She came home a year later and began voluntarily working at the Harvard Observatory. She was hired in 1902 by Edward Pickering, who gave her the job of measuring and cataloguing the brightness of stars as they appeared in the observatory's photographic glass plate collection, particularly those in the Small and Large Magellanic galaxies.
Henrietta did her work well, despite an illness that left her profoundly deaf. She was hard-working, serious-minded, little given to frivolous pursuits and selflessly devoted to her family, her church, and her career. Along the way, Henrietta identified 1,777 variable stars, or Cepheids. In 1908 she published her results in the Annals of the Astronomical Observatory of Harvard College, noting that the brighter variables had the longer period.
Using photometry, Henrietta analyzed the Great Nebula in Orion. Her work was then expanded to study the variables of the entire sky with Annie Jump Cannon and Evelyn Leland. She compared stars in different exposures and discovered that, since all those stars were approximately the same distance from Earth, their absolute brightness must allow for the use of Cepheid variables as a "standard candle" for determining cosmic distances. That, in turn, led directly to the modern understanding of the true size of the universe.
Leavitt also developed, and continued to refine, the Harvard Standard for photographic measurements, a logarithmic scale that orders stars by brightness over 17 magnitudes. She initially analyzed 299 plates from 13 telescopes to construct her scale, which was accepted by the International Committee of Photographic Magnitudes in 1913. That year, Leavitt discovered T Pyxidis, a recurrent nova in Pyxis, and one of the most frequent recurrent novae in the sky with eruptions observed in 1890, 1902, 1920, 1944, 1967, and 2011.
In 1921, when Harlow Shapley became director of the observatory, Henrietta was promoted to head of stellar photometry. By the end of that year, however, she died of stomach cancer at fifty-three years old, and was buried in the family plot in the Cambridge Cemetery.
Henrietta's research allowed future scientists to make further discoveries in space. Her friend, astronomer Edwin Hubble, used Leavitt's method to calculate the distance of the nearest galaxy to the earth, the Andromeda Galaxy. This led to the realization that there are even more galaxies than previously thought, and provided evidence that "spiral nebulae" are independent galaxies located far outside of the Milky way.
Thus, Leavitt's discovery would forever change humanity's picture of the universe, as it prompted Harlow Shapley to move the Sun from the center of the galaxy in the "Great Debate" and Edward Hubble to move the Milky Way galaxy from the center of the universe. Henrietta's discovery of a way to accurately measure distances on an inter-galactic scale paved the way for modern astronomy's understanding of the structure and scale of the universe. Hubble often said that Leavitt deserved the Nobel Prize for her work.
At the time of her death, Henrietta was unaware that her life's research would lay the foundation for the next level of space exploration. Although quiet and studious, she was known as someone who delighted in the Creator who knows every star by name, every intimate detail of His marvelous Creation. Her devotion was to God alone. She was a peaceweaver, a pathfinder, a star-charter, and all of her life pointed to Him.
-Karen O'Dell Bullock
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