Hearty Congratulations from AskPhysics Team to  Saul Perlmutter, Brian Schmidt and Adam Riess for winning the 2011 Nobel Prize for Physics for the discovery that the rate of expansion of the universe is increasing & a measurement that rocked the physics community in 1998 and led to the murky concept of dark energy.

Click Here to read about all Nobel Laurates in Physics
Read the basic information about the discovery of the accelerating expansion of the Universe through observations of distant supernovae here.

Saul Perlmutter
The Supernova Cosmology Project
Lawrence Berkeley National Laboratory and University of California,
Berkeley, CA, USA

Brian P. Schmidt

The High-z Supernova Search Team
Australian National University,
Weston Creek, Australia

and

Adam G. Riess
The High-z Supernova Search Team
Johns Hopkins University and Space Telescope Science Institute,
Baltimore, MD, USA