Vera Rubin, who helped discover evidence of dark matter, died at 88 years old on Sunday night. The astronomer and physicist died of natural causes, according to her son. Rubin's work confirmed the existence of dark matter, which is an invisible material that comprises more than 90 percent of the universe. Rubin was awarded top prizes in her field, including the National Medal of Science. In recent years, a controversy was stirred up after the Nobel committee didn't award a prize to Rubin.
