Riess, Adam Guy (1969-…), an American astrophysicist, shared the 2011 Nobel Prize in physics for the discovery that the expansion of the universe is accelerating. Riess shared the prize with the American astrophysicists Saul Perlmutter and Brian Schmidt. Riess and Schmidt worked on the same team. Perlmutter worked on a different project that made the same discovery.
The discovery is based on observations of a 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) .
Riess and Schmidt worked as members of a team formed in 1994 to search for distant supernovae. After finding and studying around 20 supernovae, the team 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 this discovery 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 ).
Adam Guy Riess was born on Dec. 16, 1969, in Washington, D.C. He graduated from the Massachusetts Institute of Technology in Cambridge, Massachusetts, in 1992. He received his Ph.D. degree from Harvard University in Cambridge in 1996. Riess was a Miller Fellow at the University of California at Berkeley before joining the Space Telescope Science Institute in 1999. He joined the faculty of Johns Hopkins University in Baltimore as a professor in 2006.
See also Perlmutter, Saul ; Schmidt, Brian Paul .
