Daughters of the Stars

 

NGC 6357. Image credit: X-ray: NASA/CXC/PSU/L. Townsley et al; Optical: UKIRT; Infrared: NASA/JPL-Caltech

NGC 6357.
Image credit: X-ray: NASA/CXC/PSU/L. Townsley et al; Optical: UKIRT; Infrared: NASA/JPL-Caltech

Galileo Galilei, Nicolaus Copernicus, Johannes Kepler, William Herschel, and Edwin Hubble.  Perhaps these names sound familiar, and for good reason. Each made profound advancements in astronomy.  Copernicus first proposed that the solar system was heliocentric rather than geocentric.  Galileo fiercely defended the Copernican model, is credited with creating the optical telescope, and discovered the four Galilean moons orbiting Jupiter as well as Saturn’s major ring system. Kepler’s three laws of planetary motion continue to stand the test of time. Herschel recorded over 2,500 deep sky objects, discovered Uranus, and the Martian ice caps. Hubble discovered the existence of other galaxies besides the Milky Way as well as the expansion of the universe.  The accomplishments of these astronomers are certainly worthy of awe and due respect.  As diverse as their achievements are, there is one other common link between them aside from their scientific research; they are all men.

Is there a reason for such a pattern? Were women capable of making equally important discoveries as men amongst the stars?

Henrietta Leavitt, Williamina Fleming, Annie Cannon, and Cecilia Payne.  Perhaps these names are vaguely familiar.  Yet these were female astronomers who, just like their male contemporaries, profoundly transformed how we see the universe.

It was not capability which limited a woman’s ability to perform scientific research, but rather archaic traditions which often restrained her from the right to decent wages and access to formal education.  In the case of Caroline Herschel, she proved that by assisting her brother, William Herschel, she could conduct the same techniques and research just as well as male amateur astronomers of the 19th century, without formal schooling. She was the first woman to discover a comet.

Many women could not break free from the constraints of household work. Until the 20th century, daughters were expected to marry, not go to school.  Combined with patronization and low wages, the female social norms for most of history made it nearly impossible for women to pursue independent scientific research.

Early female astronomers fortunate enough to have access to the proper resources and the time to conduct research often struggled to receive credit for their work. Now that we live in a time were women are slowly receiving greater equality in the scientific community, it is time to acknowledge the work of our female predecessors.  We have no excuse to shroud their names in darkness any longer.

 

Henrietta Leavitt. Credit: American Institute of Physics, Emilio Segrè Visual Archives

Henrietta Leavitt. Credit: American Institute of Physics, Emilio Segrè Visual Archives

Henrietta Leavitt

(1868-1921)

Born in Cambridge, Massachusetts as the daughter of a Congregational minister, Henrietta Leavitt went on to attend Oberlin College and the Society for Collegiate Instruction of Women (now known as Radcliffe College). She had just begun to pursue astronomy during her senior year in 1892 when she was forced to spend several years at home due to a severe illness. She recovered, but not without losing her hearing. Henrietta, however, could still see the stars.

Starting in 1895, she volunteered at the Harvard College Observatory. Henrietta worked with many other women, referred to as “computers”, since their responsibility was to collect and analyze empirical data of the stars documented from the Henry Draper Memorial.  While studying and recording more than 2,400 variable stars (nearly half of the known total at the time), Henrietta discovered a relationship between the time it took the star’s brightness to fluctuate and its actual luminosity. The class of stars Henrietta studied were Cepheid’s, a type of variable star with observed rapid changes in brightness, making it challenging to determine their distance from Earth. Henrietta determined that the Cepheid’s fluctuation in brightness is inversely proportionate to its magnitude; the stronger the star, the slower its bright-dim cycle. From this she developed the stellar relationship, known as the Cepheid variable period luminosity. She later derived a period-luminosity ratio which applied to all Cepheid stars, equipping astronomers to calculate the distance between Earth and visible Cepheid stars.

Edward Pickering was the head astronomer at the Harvard College Observatory who recruited Henrietta to his team of female computers. Aware of Henrietta’s profound accomplishments, he did not allow her to further pursue her advancements. Pickering would not allow one of his computers to stray from his assigned research. Only after seven years of volunteering did he hire her at 30 cents per hour, an income equivalent to a mere $7.98 today. She passed away at age fifty-three to cancer.  A colleague remembered Henrietta as, “possessing the best mind at the Observatory”.

 

Williamina Fleming. Courtesy Curator of Astronomical Photographs at Harvard College Observatory.

Williamina Fleming.
Courtesy Curator of Astronomical Photographs at Harvard College Observatory.

Williamina Fleming

(1857-1911)

Originally from Scotland, Williamina Fleming and her husband immigrated to the United States in 1878.  Her husband abandoned her during pregnancy, forcing Fleming to find work to support her soon-to-be son.  She found work with Edward Pickering as a maid.  In 1881, he hired her as a full-time computer at the Harvard College Observatory. Fleming’s job was to examine spectra, the breakdown of a star’s wavelengths of light, captured on photographic plates.

Pickering would place a prism in front of the telescope lens in order to record a star’s spectra on a photographic plate.  Unlike the colored lines of today’s spectra, Fleming examined plates with grayscale lines. She developed one of the first systems to classify stars into 22 groups based on their spectral lines, known as the “Pickering-Fleming System”.  Using her system, Fleming cataloged more than 10,000 stars within nine years. She went on to discover the existence of white dwarfs, as well as 10 novae, 52 nebulae, and 310 variable stars.

Fleming received considerable recognition for her efforts in the astronomical community.  In 1906, the Royal Astronomical Society elected Fleming into the organization, making her the first American female member. Possibly even more remarkable is how she made such profound discoveries without formal education in astronomy.  Fleming died of pneumonia in 1911.

 

Portrait of Annie Cannon in 1922. Credit: http://www.britannica.com/EBchecked/topic/92776/Annie-Jump-Cannon

Portrait of Annie Cannon in 1922. Credit: http://www.britannica.com/EBchecked/topic/92776/Annie-Jump-Cannon

Annie Cannon

(1863-1941)

Born in Delaware, as a young girl Annie Cannon’s mother taught her the constellations.  Her interest in astronomy grew, and Cannon studied physics and astronomy at Wellesley College. After graduating in 1884, she attended Radcliffe College for two years in order to continue studying the cosmos.

At the Harvard College Observatory, still under leadership by Edward Pickering, Cannon joined the same team of computers as Williamina Fleming.  Cannon studied the spectral signatures of stars in the southern hemisphere.  In trying to classify them, she realized that certain subtle characteristics of the star’s signatures did not match any of the classes within the Pickering-Fleming System or the more theoretical system developed by Antonia Maury. In order to accommodate and classify her stellar signatures, Cannon combined, refined, and simplified both known systems.  Stars were organized into spectral classes O, B, A, F, G, K, and M, later interpreted as the decreasing surface temperatures of the stars.

Spectra signatures like those the female computers of the Harvard College Observatory analyzed. Credit: http://spiff.rit.edu/

Spectra signatures like those the female computers of the Harvard College Observatory analyzed. Credit: http://spiff.rit.edu/

Cannon went on to catalogue variable stars, including the 300 she discovered. In total, she classified nearly a quarter of a million stars (225,000) due to her remarkable speed and accuracy. Within one minute, Cannon could classify up to three stars. Her remarkable work was published over the course of nine volumes in the Henry Draper Catalogue. In the American Astronomical Society, Cannon was the first woman to hold an officer position. She was also the first woman to receive an honorary doctorate from the University of Oxford. Just a year after her retirement, Annie Cannon passed away in 1941.

 

Cecilia Payne at Harvard. Photo: Smithsonian Institution

Cecilia Payne at Harvard. Photo: Smithsonian Institution

Cecilia Payne 

(1900-1979)

Born in England, Cecilia Payne began studying at Cambridge University. During one of the public observation nights at the Cambridge Observatory, Payne reportedly was so fascinated and asked the attendees so many questions that someone fetched Professor Eddington in order to satisfy her curiosity.  Eddington recommended a series of books after learning she desired to become an astronomer, but to his surprise Payne had already read them all.  Seeing her talent, Eddington allowed Payne access to the latest astronomical journals at the Observatory’s library. After realizing that England only saw a female astronomer as worthy of a teaching position, Payne immigrated to the United States in 1923 with hopes to pursue her own research.

Harlow Shapley, Edward Pickering’s successor at the Harvard College Observatory, offered Payne a graduate fellowship.  Payne studied the absorption lines of stellar spectra, like many of the Observatory’s computers. However, Payne was offered the freedom to independently interpret the spectra rather than being held to the constraints of empirical analysis as the computers were. Payne applied her knowledge of the newly emerging quantum physics to spectra. She understood that the linear patterns of spectra were determined by the configuration of an atom’s electrons. Also, she was aware that a new discovery, revealed by Meghnad Saha, demonstrated how at extremely high temperatures, one or more electrons is stripped from atoms, forming ions. After two years of intense research, Cecilia combined spectral analysis with quantum physics to conclude the composition of the stars was not primarily heavy earth elements, as previously thought by astronomers, but rather mostly hydrogen followed by helium, with small percentages of heavier elements. The variation of the stars’ spectral lines was due to differing ionization states of atoms and therefore different stellar surface temperatures, not the amount of elements present.  Payne’s method of discovering the composition of the stars was a pioneering achievement in the burgeoning study of astrophysics.

Payne published her discovery as her senior thesis. Harlow Shapley sent her thesis to Professor Henry Russell at Princeton University, who concluded that if Earth’s crust, primarily composed of heavy elements, were heated to the Sun’s temperature, its spectra would match that of the Sun. Incredulous that his theory could be proven wrong, and worse, by a woman, Russell sent word to Shapley that Payne’s conclusion was “clearly impossible”.  Fearing the impact this would have on her reputation and career, Payne felt she must add to her thesis that her calculated presence of hydrogen and helium were “almost certainly not real”.

Not to be dissuaded by Russell’s disapproval, Payne went on to publish the thesis in her book, Stellar Atmospheres.  It was well received by astronomers, and soon her findings were widely accepted.

After completing her Ph.D., Payne lectured, advised students, and further conducted research at the Harvard College Observatory. Although these duties should have earned her the title of professor, Payne’s status remained a “technical assistant” to Harlow Shapley. Only in 1956 did she finally received the well-earned title as a full-time professor and chair of the Astronomy Department. Payne was the first woman to earn both.  Ironically, she went on to win the Henry Norris Russell Prize in 1976.

 


Published by Julia Mariani

Sources:

http://www.amnh.org/explore/resource-collections/cosmic-horizons/profile-cecilia-payne-and-the-composition-of-the-stars

https://www.aps.org/publications/apsnews/201501/physicshistory.cfm

http://www.biography.com/people/annie-jump-cannon-9236960#creating-a-spectral-classification-system

http://ocp.hul.harvard.edu/ww/fleming.html

http://www.smithsonianmag.com/history/the-women-who-mapped-the-universe-and-still-couldnt-get-any-respect-9287444/

http://www.space.com/17439-caroline-herschel.html

https://www.sdsc.edu/ScienceWomen/cannon.html

http://www.nls.uk/learning-zone/science-and-technology/women-scientists/williamina-fleming

http://www.pbs.org/wgbh/aso/databank/entries/baleav.html

http://www.famousscientists.org/henrietta-swan-leavitt/

 

 

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