Vera Rubin

Born on 23 July 1928 in Philadelphia, Vera Rubin was an astronomer who confirmed the existence of dark matter. After earning her PhD from Georgetown University in 1954, Rubin stayed on to teach. In 1965 she joined the department of terrestrial magnetism at the Carnegie Institution of Washington, where she would remain for the rest of her career. In the 1960s and 1970s, Rubin and her colleague Kent Ford studied galactic rotations using an image-tube spectrograph that captured astronomical observations electronically. From those observations, they found a discrepancy between the observed mass distribution of the galaxies and their rotation curves. The velocities of stars did not appear to vary relative to their radial distance from the galaxy’s center, but rather remained constant. That finding indicated the presence of additional, hidden matter, dubbed dark matter. Today dark matter is thought to account for nearly 90% of all matter in the universe. Rubin continued to study galaxy dynamics and large-scale structure throughout her career.

Rubin’s successes came at a time when some astronomy programs still did not admit women, and women were often denied access to key equipment, such as telescopes. In 1965 Rubin became the first woman allowed to use the 200-inch Hale Telescope at California’s Palomar Observatory, the largest telescope in the world at that time. In 1981 Rubin became only the second female astronomer to be elected to the National Academy of Sciences, and in 1996 she became only the second woman, after Caroline Herschel in 1828, to receive the Gold Medal of the Royal Astronomical Society. Although Rubin was honored with many awards, including the US National Medal of Science in 1993, she never received the Nobel Prize. Besides being a pioneering scientist, Rubin served as a mentor, role model, and advocate for women in astronomy. She died in December 2016 at age 88. (Photo credit: AIP Emilio Segrè Visual Archives, John Irwin Slide Collection)

Date in History: 23 July 1928