Vera Rubin

Vera Rubin (born July 23, 1928, Philadelphia, Pennsylvania, U.S.—died December 25, 2016, Princeton, N.J.) was an American astronomer known for her research on galaxy rotation rates, which provided evidence for the existence of dark matter. Dark matter is a component of the universe whose presence is discerned from its gravitational attraction rather than its luminosity, and it accounts for about 85 percent of the matter in the universe. She was also a pioneer in the field of women astronomers.

Family and childhood

Vera Cooper was the younger of two daughters of Jewish immigrants from eastern Europe. Her father, Pesach Kobchefski (who later anglicized his name to Philip Cooper) was born in Vilnius, Lithuania. He was an electrical engineer and worked for Bell Telephone, where he met Rose Applebaum (who emigrated from Bessarabia, now Moldova). They married and had two children.

The family eventually moved to Washington, D.C., where young Vera Cooper became interested in astronomy while watching the stars from her bedroom window. Her parents encouraged their daughter to study the stars, and her father helped her build her first telescope.

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Education and early career

Cooper attended the then all-women Vassar College on scholarship. She graduated Phi Beta Kappa, the oldest honor society in the United States, and earned her bachelor’s in astronomy in 1948. She was the only astronomy major to graduate that year from Vassar. That same year, she married Robert Joshua Rubin, an American mathematician who was then a graduate student in chemistry at Cornell University.

Vera Rubin tried enrolling in Princeton University for graduate study but was rejected because of her gender. She was accepted into Harvard University’s program, but she turned it down in favor of Cornell so that she could be close to her husband. Rubin later recounted that she had received a letter from the Harvard Observatory’s director, Donald Menzel, in which he had handwritten at the bottom of the otherwise very formal letter, “Damn you women. Every time I get a good one ready, she goes off and gets married.”

The supergalactic plane, dark matter, and legacy

Rubin earned her master’s from Cornell in 1951. Her research involved studying the motion of 109 galaxies, including the Milky Way. Rubin theorized that there was an orbital motion of galaxies around a particular pole, and she found a plane that was denser with galaxies than other regions. This is now known to be evidence of the supergalactic plane, which contains the Local Supercluster of galaxies.

When Rubin had presented her thesis to her adviser, he suggested that she present her evidence to the American Astronomical Society (AAS) meeting but that someone else present it, as Rubin was pregnant with her first child and was not a member of the AAS. He suggested that he present her thesis in his name. She declined the suggestion and presented her findings to the AAS herself, nine months pregnant, under the audacious title “Rotation of the Universe.” The audience was extremely skeptical of her findings, and only a brief abstract of her thesis was published.

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After the birth of her first child, Rubin was accepted to the doctoral program at Georgetown University in Washington, D.C., with George Gamow as her adviser. (A few years earlier, Gamow had contacted Rubin to inquire about her work on galaxy rotation but would not allow her to attend his lectures because “wives were not allowed.”) She completed her dissertation in 1954. Her doctoral research was one of the earliest observations of the clustering of galaxies. She concluded that galaxies were not randomly distributed; instead the galaxies clumped together. Her work would go largely unrecognized until the 1970s.

In 1965 Rubin began her work at the Carnegie Institution’s Department of Terrestrial Magnetism in Washington, D.C. There, she worked with astronomer W. Kent Ford on studying the rotation of the Andromeda Galaxy. They expected stars to orbit around the center of the galaxy as planets in the solar system do around the Sun. Objects closest to the center will orbit faster than objects farther away, because most of the solar system’s mass is centrally concentrated in the Sun. They observed areas of ionized hydrogen gas where stars have recently formed, known as H II regions, and found that no matter the distance from the galaxy’s center, objects were moving at the same orbital velocity.

The mass required to keep the H II regions moving at such a speed was 10 times the mass that could be seen in the visible stars and gas. Rubin showed that this was because much of the mass of the galaxy was not concentrated in the center, but spread throughout the galaxy and could not be seen: a halo of dark matter permeated the galaxy. This would cause the orbital speed to remain relatively constant throughout. The existence of dark matter was previously only a conjecture but was confirmed through Rubin’s work. Rubin and her collaborators observed dark matter halos in many other galaxies.

Legacy

Rubin died because of complications associated with dementia. She was awarded the National Medal of Science in 1993 and was frequently mentioned as a candidate for the Nobel Prize. The Carnegie Institution created a postdoctoral research fund in her honor, and the AAS’s Division of Dynamical Astronomy named the Vera Rubin Early Career Prize in her honor. In December 2019 the Large Synoptic Survey Telescope was renamed the Vera C. Rubin Observatory in recognition of her work. It is currently under construction in Chile. When it starts observing in 2025, it will take pictures of the entire visible sky every few nights.