Allan R. Sandage, who spent his life measuring the universe, becoming the most influential astronomer of his generation, died Saturday at his home in San Gabriel, Calif. He was 84. The cause was pancreatic cancer, according to an announcement by the Carnegie Observatories, where he had spent his whole professional career.
Over more than six decades, Dr. Sandage was like one of those giant galaxies that sit at the center of a cluster of galaxies, dominating cosmic weather. He wrote more than 500 papers, ranging across the cosmos, covering the evolution and behavior of stars, the birth of the Milky Way galaxy, the age of the universe and the discovery of the first quasar, not to mention the Hubble constant, a famously contested number that measures the rate of expansion of the universe.