Harvard Computers: The Women Who Mapped the Sky

Talk given to a few audiences in Feb2018 and May2018

Transcript

1. The Harvard Computers: The Women Who Mapped the Sky Jennifer Sobeck (@oneillleo ; http://staff.washington.edu/jsobeck/Home.html ) University of Washington With Special Thanks to: R. Beaton (Carnegie-Princeton), O. Fraser (UW), L. C. Smith (Harvard Libraries) May 19, 2018
2. If I have seen further, it is by standing on the shoulders of Giants. - Sir Issac Newton Science is accomplished by standing on the shoulders of previous contributors. My “giant”: Charlotte Moore Sitterly Princeton “Computer” Compilation of Solar Wavelength and Multiple Tables It is important to know exactly whose shoulders we are standing upon…
3. Harvard Computer History ✴1876: The fourth Harvard Observatory director, Edward Charles Pickering, is appointed. He remains the Harvard College Observatory (HCO) director for nearly 40 years. ✴1860’s-1870’s: Women, like Eliza Quincy, daughter of founder Josiah Quincy, were only given volunteer status as observers at Harvard Observatory, though several women had applied to work as student assistants. ✴1875: Harvard Observatory begins admitting women as staff. Some of the earliest women to officially work at the observatory include R.T. Rogers, R.G. Saunders and Anna Winlock, who all assisted William A. Rogers in his project regarding time zones. Saunders remains at the observatory for 13 years. Harvard computers, circa 1890. Seated, third from left, with magnifying glass: Antonia Maury; standing, at center: Williamina Fleming
4. Harvard Computer History ✴1877+: Edward Pickering begins hiring women computers on a regular basis. The women are paid 25-30 cents an hour and work 6 days per week. ✴1879: Radcliffe College, Harvard’s sister school for women, is founded. ✴1886- After Anna Draper fails to find someone to complete the work in her own observatory. she collaborates with Pickering and donates funds and equipment to the Harvard Observatory to support a department of stellar spectroscopy. The studies in stellar spectra became known as the Henry Draper Memorial, in honor of her husband. Anna Draper is largely responsible for funding the corps of women computers. ✴1882: Pickering orders ongoing photographic stellar investigations, creating the astronomical photographic plate collection. Harvard computers, 1913, standing in front of Building C at the Harvard College Observatory. Pickering is standing in the back. Harvard College admitted women students in 1977.
5. Harvard College Observatory + Photographic Plates ✴The Harvard College Observatory (HCO) houses the world’s largest collection of glass plates. ✴Plates contain either photo-negative images (~450,000 plates) or spectra (~100,000 plates) of the stars over the full sky (Northern and Southern Hemispheres). ✴The plates were taken by more than 20 Harvard telescopes in the US, Peru, S. Africa and others from 1885-1992. ✴The Harvard Women Computers catalogued and analyzed these plates (primarily from 1890 – 1940).
6. Henrietta Swan Leavitt Henrietta Swan Leavitt 1868 - 1921 ✴1907: Henrietta Swan Leavitt, a Radcliffe College alumuna, started volunteering at Harvard Observatory, working seven years for no pay. ✴She was a classifier who was specifically tasked with studying "variable stars", whose luminosity (brightness) varied over time. ✴Leavitt’s most common method was through superposition, placing one negative atop another that was taken at a later date. ✴During her career, Leavitt discovered roughly 2,400 variable stars (half of *all* known variable stars at the time of her death). Nearby Variable Star, RS Puppis (Cepheid) Leavitt-Examined Plate of Variable Star, Delta Crux
7. Henrietta Swan Leavitt ✴1908: She published a catalog of 1777 variable stars that had been identified in this way in both the Large and Small Magellanic Clouds. ✴These images were more sensitive than previous images and Leavitt made an observation in the catalog description highlighted here than “the periods of many of the [fainter] variables are short”. Henrietta Swan Leavitt 1868 - 1921 Leavitt discovers Cepheid stars.
8. Henrietta Swan Leavitt Henrietta Swan Leavitt 1868 - 1921 Maximum Brightness Minimum Brightness Short Period Long Period Brightest Stars Faintest Stars ✴Leavitt presented this figure that plotted the maximum (orange) and minimum (red) magnitudes reached by each of the Cepheids as a function of their period. ✴She finds “a remarkable relation between the brightness of these variables and the lengths of their periods will be noticed”. She draws the conclusion, “…there is a simple relation between the brightness of the variables and their periods.” ✴Leavitt went on to provide the first calibration of the slope of this relationship, but as there was no known distance to the MC, she could not determine the zero point.
9. Edwin Hubble: “Standing on the Shoulders of H. Leavitt” ✴1924: Edwin Hubble discovered a Cepheid in the Andromeda Nebula, and using the (Cepheid) period- luminosity relationship was able to show that it was a galaxy external to the Milky Way. ✴1929: With the use of Cepheids, he measured the local rate of expansion of the universe (Ho constant). ✴For ~100 years, prominent astronomers used Cepheids to chart the cosmos, with little to no recognition going to Leavitt. v = HO d Recession Velocity (v) Distance (d) Edwin Hubble Expansion of the Universe Lower Right: Hubble’s M31 Plate
10. Annie Jump Cannon Annie Jump Cannon 1863-1941 ✴1898: Annie Jump Cannon begins volunteering at the Observatory while taking graduate classes at Radcliffe. She is mostly deaf due while a student at Wellesley. ✴1911: Pickering promotes Cannon as the second Curator of Astronomical Photographs though Harvard President Lowell refuses to allow her to be listed in the staff catalog. ✴1938: Annie Cannon is finally recognized as the Curator of Astronomical Photographs by the Harvard Corporation. ✴She averaged 3 stars a minute and was able to classify over a quarter of a million stars with speed and accuracy. Spectra of Hyades stars with an objective prism scope Cannon Notebook from the Draper Star Catalog
11. Annie Jump Cannon Annie Jump Cannon 1863 - 1941 ✴Cannon was able to refine the classification systems of Fleming and Maury, reducing the number of categories and rearranging them by temperature, leaving us with the famous OBAFGKM acronym. ✴Old, Bald, And Fat Generals Keep Mistresses (credit: Stony Brook AST 101 Class) ✴Oh Boy, An F Grade Kills Me ✴Only Boring, Astronomers Find Gratitude Knowing Mnemonics ✴She also included numbers 1-10 within each category as a finer distinction. “Each new spectrum is a gateway to a wonderful new world.” Stellar Spectral Sequence (Abt et al. 1968) HCO Plate Featuring Prism Spectra
12. Stellar Spectroscopists: “Standing on the Shoulders of Cannon” ✴Cannon's system was adopted as the standard in 1910 by the International Astronomical Union, and today with only minor changes it is known as the Harvard Spectral Classification.
13. Cecilia Payne-Gaposchkin Cecilia Payne-Gaposchkin 1900 - 1979 ✴She studied but could not receive a degree from Cambridge. ✴1925: Cecilia Payne-Gaposchkin becomes the first person to earn a PhD in Astronomy from Harvard, though, as a woman, her degree officially comes from Radcliffe. The university creates the degree especially for Payne-Gaposchkin. ✴1956: She worked for approximately 30 years to transition from PhD recipient to professor. ✴Payne-Gaposchkin eventually became the first women to head a department at Harvard. Notes from Payne- Gaposchkin on Lines Multi-wavelength view of the Sun
14. Cecilia Payne-Gaposchkin Cecilia Payne-Gaposchkin 1900- 1979 ✴1925: Payne discovered that the atmosphere of the sun is made mostly of hydrogen and helium (approximately 98% of the total solar mass), in contrast to the popular view that the sun had the same composition as the Earth (“Stellar Atmospheres: A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars”, 1925, Ph.D. Thesis, Radcliffe). ✴She observed the Stark Effect (line splitting) for the first time in solar spectra. ✴Payne showed that the many differences in the lines of stellar spectra were due in large part to the different atomic ionization states and hence different temperatures (Saha-Boltzmann)—> and not to different amounts of elements. Solar Absorption Spectrum with Line Identifications Periodic Table of Elements
15. Henry Norris Russell: “Standing on the Shoulders of Payne” ✴1925: Russell initially did not believe Payne’s finding that the atmosphere of the sun is made mostly of hydrogen and helium and stated this in a letter to her. ✴1929: He later changed his mind after having derived the same result and publishing it (“On the Composition of the Sun’s Atmosphere”, 1929, ApJ, 70, 11), acknowledging Payne's previous work somewhat in his paper (of the 72 page work, the first substantial reference to Payne starts on page 64). ✴Russell is still often given credit for this monumental discovery. Henry N. Russell
16. Project PHaEDRA Preserving Harvard's Early Data and Research in Astronomy https://transcription.si.edu/browse?filter=owner%3A11&sort= PHaEDRA: Shows how the women made their discoveries which transformed Astronomy Transcription of ~2,400 Notebooks https://library.cfa.harvard.edu/project-phaedra
17. Project DASCH DASCH: Extends these discoveries of the Harvard Computers into the era of modern Astrophysics and Big Data http://dasch.rc.fas.harvard.edu/ Digital Access to a Sky Century @ Harvard
18. Several Generations of Computers…
19. “...so if we want to get to our...best possible discoveries, then everyone has to have a seat at the table" From @JedidahIslerPhD This is just the tip of the iceberg.