Rubin, Vera (1928-2016), an American astronomer, discovered key evidence to support the theory of dark matter. Dark matter is an invisible form of matter thought to make up as much as 90 percent of the matter in the universe. The Swiss astrophysicist Fritz Zwicky first suggested the existence of dark matter in 1933.
Rubin made her discovery working with the American astronomer W. Kent Ford, Jr. During the 1950’s, Ford developed a sensitive spectrometer to measure starlight. A spectrometer separates light into a spectrum (range of wavelengths) in much the same manner as does a prism. By studying the spectrum of light coming from certain stars, scientists can determine the stars’ Doppler shift. Doppler shift is a variation in the wavelength of light from a moving object. It can indicate the speed and direction of the object’s movement.
Using the new spectrometer, Rubin and Ford calculated the speed at which stars in different galaxies orbit the center of those galaxies. The more massive a galaxy, the stronger its gravitational attraction, and thus the faster the stars move around the center. In principle, then, scientists can calculate the mass (amount of matter) of a galaxy by measuring the orbital speed of its stars.
Rubin and Ford conducted a study of about 60 spiral galaxies. They found that the orbital speed of the stars in these galaxies was far higher than expected. Their finding implied that the mass astronomers could see in a galaxy was only about 10 percent of its total mass. Without huge amounts of extra mass, the fast-moving outer stars would escape the galaxy’s gravitational pull. These findings support Zwicky’s study suggesting that some form of dark matter held these galaxies together.
Vera Cooper was born on July 23, 1928, in Philadelphia. She earned a scholarship to Vassar College in New York. She graduated in 1948 as the college’s only astronomy major. After graduation, she married the American physicist Robert Rubin. In 1951, Vera Rubin earned her M.S. degree from Cornell University in New York. She earned her Ph.D. degree from Georgetown University in Washington, D.C., in 1954. She taught at Georgetown before becoming a researcher at the Carnegie Institution of Science in Washington, D.C. Rubin was elected to the National Academy of Sciences in 1981. In 1993, she won the National Medal of Science. Rubin died on Dec. 25, 2016.
In 2019, the Large Synoptic Survey Telescope, located in Cerro Pachon, Chile, was renamed the Vera C. Rubin Observatory in her honor. It became the first national observatory to be named after an American woman.
See also Dark matter .
