Prof. Robert P. Kirshner, Harvard University, USA

Prof. Robert P. Kirshner, Harvard University, USA Winner of Wolf Prize in Physics - 2015
Prof. Robert P. Kirshner, Harvard University, USA

This year's Wolf prize in physics is awarded to two researchers who made fundamental contributions toward understanding the structure of the Universe at the very smallest and the very largest sizes: James D. Bjorken: For predicting scaling in deep inelastic scattering, leading to identification of nucleon's pointlike constituents Robert Kirshner: For forging the path to supernova cosmology through his observations and insights

Robert Kirshner has devoted his professional life to cutting-edge research on cosmology and supernovae. He created the group, environment and directions that allowed his graduate students and postdoctoral fellows to uncover the acceleration in the expansion of the universe.  This discovery is a landmark in fundamental physics, as well as in astronomy, and presents a profound challenge to theorists.

In 1974, Prof. Kirshner invented, with John Kwan, a method to measure the expansion rate of the universe based on observations of supernovae. Many key roadblocks, especially the effects due to reddening by interstellar dust, had to be overcome before supernovae could be used as a standard candle of sufficient accuracy to detect any change in the expansion rate.  In the 1980s, Kirshner's program of monitoring supernova explosions in a suite of wavelengths was the world's most extensive and led to SNIa becoming widely accepted as the best for cosmological investigations. This  was an essential step for the later discovery of the acceleration of the expansion.

Kirshner also led a program in which ultraviolet spectra of SNIa's were measured with the Hubble Space Telescope.  The results  enabled the effects of redshift on the light ("photometry") from supernovae at different distances to be properly corrected.  All supernova cosmology teams now use these essential data.

Prof. Kirshner guided the formation of the High Z Supernova Team, one of the two teams widely credited with the discovery of cosmic acceleration.  He gathered a first-rate group of students, such as Brian Schmidt and Adam Reiss,  and led them toward practical and effective steps to find and follow SN Ia in a way that could reliably reveal cosmic deceleration, as was then almost the universally-expected result.  Especially important was Kirshner's insistence that the data at more than one colour be obtained to allow separation of dust from cosmic-motion effects in the photometry data.