Perlmutter, Saul (1959-…), an American astrophysicist, shared the 2011 Nobel Prize in physics for the discovery that the expansion of the universe is accelerating. Perlmutter shared the prize with the American astrophysicists Adam Riess and Brian Schmidt, who made the same discovery working on a different project.
The discovery is based on observations of a certain kind of exploding star called a Type Ia supernova. All Type Ia supernovae are thought to be of a similar size and luminosity (brightness). These similarities enable scientists to accurately calculate the distance to a Type Ia supernova by measuring its apparent brightness as seen from Earth. See Supernova (Thermonuclear supernovae) .
Perlmutter began his observations of supernovae in the 1980’s. In 1988, he became the head of a project studying distant supernovae at the Lawrence Berkeley National Laboratory in Berkeley, California. After gathering data from many supernovae, Perlmutter and his colleagues determined that the distant Type Ia supernovae appear dimmer—and thus farther away—than expected. This evidence suggests that the expansion of the universe is speeding up. The team announced their results in 1998. Scientists had long known that the universe was expanding, but they expected the expansion to be slowing due to gravitational attraction among the universe’s matter. The discovery of the acceleration has led many scientists to believe that a mysterious form of energy, which they named dark energy, is driving the universe apart (see Dark energy ).
Saul Perlmutter was born on Sept. 22, 1959, in Champaign-Urbana, Illinois. He graduated with a B.A. degree from Harvard University in Cambridge, Massachusetts, in 1981. He received his Ph.D. degree in physics from the University of California at Berkeley in 1986. Perlmutter later became a professor at Berkeley in 2004.
See also Riess, Adam Guy ; Schmidt, Brian Paul .
