In the 1970s, astronomer Vera Rubin found evidence of a hypothetical type of invisible matter now called dark matter.
She discovered that the stars at the edges galaxies moved faster than expected. Gravity calculations using only the visible matter in the galaxies showed the outer stars should have been moving more slowly. Unseen dark matter was the predicted cause of the discrepancy.
The astronomer Fritz Zwicky had previously predicted the existence of invisible matter in the 1930s following his observations of the Coma galaxy cluster.
Image: Vera Rubin measuring spectra (Emilio Segre Visual Archives/AIP/SPL)
Rubin finds evidence of invisible matter.
Vera Rubin's star velocity measurements support theory.
Measurements of the velocities of stars orbiting in galaxies made by Dr Vera Rubin in the 1970s are evidence of dark matter's existence. Dark matter is thought to provide the "extra gravity" needed to reconcile the orbits of stars with Newton's law of gravity.
Vera Rubin (née Cooper; born July 23, 1928) is an American astronomer who pioneered work on galaxy rotation rates. She uncovered the discrepancy between the predicted angular motion of galaxies and the observed motion, by studying galactic rotation curves. This phenomenon became known as the galaxy rotation problem. Although initially met with skepticism, Rubin's results have been confirmed over the subsequent decades. Attempts to explain the galaxy rotation problem led to the theory of dark matter.