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Vera Rubin, linocut on Japanese paper, 11" x 14", by Ele Willoughby, 2023. The orbital velocity of galaxies is plotted against distance (on top of a galaxy, from its centre outwards). There's a wide gulf between the drop off that would be predicted by Kepler's laws and what was observed. Here, I have left that region white to emphasize that it was evidence of something missing and unseen. So I selected her for the #printerSolstice prompt space, so I could allude to outer space and have the space within the composition be what was telling the story.
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This is a linocut print of renown astronomer Vera Rubin (neé Cooper, 1928-2016) and her discovery that the angular motion of galaxies deviates considerably from predictions, which we now know was the first evidence for dark matter, confirmed in the decades since.
Her parents, Eastern European Jewish immigrants, electrical engineer Pesach Kobchefski (anglicized to Philip Cooper) from Lithuania, and Rose Applebaum from what is now Moldova, met in Philadelphia, working at Bell Telephone; though her mother's job ended when she married. When Vera was 10 they moved to Washington, DC, where she watched stars from her window and first fell in love with astronomy. “What fascinated me was that if I opened my eyes during the night, they had all rotated around the pole and I found that inconceivable. I just was captured,” she later told AIP in 1995. With her father she built a simple cardboard telescope and tracked meteors. Her older sister went to law school. After she finished high school in '44 she ignored her physics teacher's advice to pursue art rather than science and went to the women's college Vassar, where astronomy trailblazer Maria Mitchell had been a professor as early as 1865. She graduated with honours, the sole astronomy graduate of 1948.
She wanted to pursue graduate studies at Princeton but was barred due to her sex; Princeton took 27 more years to admit women astronomy graduate students. She turned down an offer from Harvard, and instead opted for Cornell where her new husband, physicist Robert Joshua Rubin was a graduate student. During her masters (Cornell, 1951) she studied the motions of 109 galaxies. Hubble flow (or the Hubble-Lemaître law) states that galaxies are moving away from us at speeds proportional to their distance. Rubin was one of the first to observe a deviation from this law. She studied under Philip Morrison, Hans Bethe, and Richard Feynman and worked with astronomer Martha Stahr Carpenter to find a thesis topic on galaxy dynamics. She said that Carpenter's "course in galaxy dynamics really set me off on a direction that I followed almost my entire career.” Her husband brought her a paper by renown physicist and cosmologist George Gamow who pondered whether galaxies moved like solar systems and it inspired her to start investigating how galaxies move. She found a plane of higher density of galaxies, which years later we would recognize as was some of the earliest evidence of the super galactic plane, the equator of our supercluster of galaxies.
One of her advisors, Robert Shaw told her that her work was sloppy but should be presented to the American Astronomical Society (AAS) meeting. Since she was not a member, and very pregnant, he could do that - under his own name, not hers. So, she said she could go. She found the discussion after was acrimonious and she felt like an imposter. Her paper was never published.
She took 6 months maternity leave but found it immensely difficult being at home with their lovely baby but watching her husband going to work daily to pursue what he loved. It was her husband who insisted she return to grad school. He took a job at the National Bureau of Standards in Washington, D.C. She gained experience working summers at the Naval Research Laboratory and the US Naval Observatory. She was admitted to the PhD program at Georgetown University, the only university in Washington, D.C. with a graduate astronomy program, at age 23, expecting their second child. The Jesuit astronomer Fr. Francis Heyden taught his courses at night, a real challenge with a young family. She encountered sexism, and recounted how she was not allowed to meet her advisor in his office as women were barred from that area of the Catholic university. When writing her thesis, Heyden got her in contact with George Gamow, who worked at the nearby Applied Physics Laboratory and was an adjunct professor at George Washington University. Gamow took her on as a student. In her 1954 thesis she noted that galaxies clump together rather than being randomly distributed - a largely ignored idea it took the field decades to catch up with.
While her four children were very young, she taught at Georgetown and Montgomery College for several years before gaining a research position at the Carnegie Institution of Washington's Department of Terrestrial Magnetism (which operated the Wilson Observatory in California and had a new high-tech magnetically focused electronic image tube which could increase the sensitivity of telescopes). She worked for a year with Geoffrey and Margaret Burbidge observing rotating galaxies using the McDonald Observatory's 82" telescope. She was the first woman to use the Palomar Observatory in 1965, pragmatically solving the lack of washrooms by claiming one by going to her room, cutting out a little paper skirt and pasting it to the little man icon on the door. "There you go; now you have a ladies' room." At Carnegie she met physicist and astronomical instrument maker Kent Ford. Together they made the most sensitive spectrometer of the day using the magnetically focused image tube- an instrument which divided light into its constituent frequencies and importantly allowed astronomers to study small regions of galaxies previously too dim to observe, not just galaxies in their entirety. They started looking at the newly discovered quasars but she did not enjoy the competition from astronomers with more access to world-class telescopes and the race to explain these objects. She wanted to carve out a niche to themselves. They decided to look at Andromeda Galaxy, returning to her interest in galaxy dynamics with Ford's spectrometer allowing them to see if galaxies did rotate like our solar system. Since mass and hence gravity is clustered in the centre, nearer objects should go faster than objects at the periphery. But, when they looked at areas of hydrogen gas where new stars form, at various distances from the centre of the galaxy, they all seemed to be going at the same speed. The expected drop off with distance simply wasn't there. They spent years on the project, travelling to various telescopes across the country for observing time. Rubin spent long hours analyzing data on punchcards and always seeing the same thing: no drop-off with distance from the centre of Andromeda. So they looked at other galaxies, and more and more galaxies. They gathered dozens of rotation curves and they were all flat. It contradicted theory and they did not know why but their data was undeniable. (You can see a video of how galaxies were predicted to move next to how they are observed to move here).
The concept of dark matter was proposed by Jan Oort (1932) and Fritz Zwicky (1933) to explain how physics seemed to imply more mass than astronomers could see, but they were largely ignored and no one has developed any theory of how galaxies who behave in the presence of dark matter, nor had anyone gathered observational evidence of dark matter. Rubin and Ford simply did not know what their observations meant. "One day I just decided that I had to understand what this complexity was that I was looking at, and I made sketches on a piece of paper, and suddenly I understood it all," Rubin said. A halo of dark matter - that is, matter which is not luminous, which we cannot see with telescopes, perhaps better imagined as invisible or unseeable rather than "dark," around galactic cores would spread out the mass throughout the galaxies, and hence and speeds would remain flat with distance from the centre. This unseen matter that Rubin and Ford first observed is now understood as the stuff that dictates how galaxies move, and even the origin and fate of our universe.
Since their discovery, a theoretical frame work was set out which fits their model and the Planck satellite measured dark matter by observing the cosmic microwave background. It imaged clumping in the early universe which otherwise would have been homogeneous but which instead, because of this dark matter, evolved into the superclusters of galaxies we know today. We now believe there is five times as much invisible dark matter and the luminous matter we can see. The discovery of dark matter revolutionized astronomy and lead to entire new subfields of astronomy and particle physics. She was a favourite to win the Nobel Prize for many years, but died before that ever happened. Twenty years after Rubin's research revealed dark matter, dark energy was discovered, and its discoverers received the Nobel in 2011. In 2019, three years after her death, James Peebles shared the Nobel Prize in physics for work on evolution of our universe- notably theoretical work on existence of dark matter and dark energy. Many physicists and astronomers lamented the egregious snub of Vera Rubin, by waiting until she had died rather than including her.
She also found evidence that some stars and gas within galaxies move counter to the prevailing motion, some of the first evidence of galaxy mergers.
Throughout her career she was a champion of women in science, writing, “I live and work under three basic assumptions. One: There is no problem in science that can be solved by a man that cannot be solved by a woman. Two: Worldwide, half of all brains are in women. Three: We all need permission to do science, but, for reasons that are deeply ingrained in history, this permission is more often given to men than to women.” She likewise championed scientific literacy.
She published more than 100 peer reviewed scientific papers, a collection of essays, was on the editorial boards of journals and a member of the National Academy of Sciences (the second woman astronomer admitted, after Margaret Burbidge) and won the National Medal of Science. She won the gold medal of the Royal Astronomical Society in 1996; she was only the second woman to do so, 168 years after Caroline Herschel. Carnegie named a post-doc fellowship in her honour and the American Astronomical Society named a Vera Rubin Early Career Prize. There is Vera Rubin Ridge on Mars and Asteroid 5726 Rubin, a satellite and the Vera C. Rubin Observatory named in her honour. All four of her children grew up to be PhD mathematicians and scientists and they credit their mother for making it look like desirable and fun.
References
Vera Rubin, Wikipedia, accessed January 2023.
Meet Vera Rubin, November 17, 2021, Air And Space Museum, Smithsonian Museum.
Sarah Scoles, How Vera Rubin confirmed dark matter, Astronomy, Tuesday, October 4, 2016
Matt Schudel, Vera Rubin, astronomer who proved existence of dark matter, dies at 88, Washington Post, December 26, 2016
Rachel Feltman, In memory of Vera Rubin, the woman the Nobel Prize forgot, Popular Science, December 27, 2016
Ethan Siegal, Who Really Discovered Dark Matter, Fritz Zwicky or Vera Rubin? Forbes, August 24, 2021
Chanda Prescod-Weinstein, The Disordered Cosmos, Bold Type Books, New York, 2022.
Kelsey Johnson, We're Sorry, Vera Rubin, Scientific American, October 16, 2019
Shannon Connellan, Nobel Prize in Physics awarded to scientists, some rally behind one who never got one, Mashable, October 8, 2019
