Vera Rubin, who passed away recently, was the noted astronomer of which country?
[B]United Kingdom
[C]United States

United States
Vera Rubin (88), an American astronomer who pioneered work on galaxy rotation rates, has recently passed away in Princeton, New Jersey. In 1974, Rubin discovered that the stars at the edges of galaxies moved faster than expected. She uncovered the discrepancy between the predicted angular motion of galaxies and the observed motion, by studying galactic rotation curves. To reconcile her observations with the law of gravity, scientists proposed there was matter we cannot see and called it dark matter. Dark matter is an unidentified type of matter comprising approximately 27% of the mass and energy in the observable universe.