Congratulations to the 2011 Nobel Prize Winners for Physicsby xzhang
October 12, 2011
Figure 1. Example of spectrum obtained from Gemini using Nod and Shuffle, needed to characterize many of the faintest of the supernovae studied in the SNLS.
Figure 2. Corrected absolute brightness against supernova redshift, including measurements from the SNLS, HST, the Sloan Digital Sky Survey, and other facilities. The detailed shape of the diagram especially at large redshift is evidence for the accelerating expansion of the universe. (Figure credit: A. Conley et al. 2011 Astrophysical Journal Supplement Series 192:1.)
The staff of the Gemini Observatory wish to congratulate the winners of the 2011 Nobel Prize for Physics: Saul Perlmutter (Lawrence Berkeley National Laboratory and University of California, Berkeley), Brian P. Schmidt (Australian National University), and Adam G. Riess (Johns Hopkins University and Space Telescope Science Institute, Baltimore). The Nobel prize citation recognizes two teams for the discovery of the accelerating expansion of the universe based on observations of supernovae (SN). Since the original discoveries, both teams have used Gemini data to pursue their studies, especially as part of the Supernova Legacy Survey (SNLS) and the ESSENCE survey.
The origin of the acceleration is also known as dark energy, and its further study requires the power of the world's largest and most sensitive telescopes to characterize distant supernovae in the early universe. Once characterized, these exploding stars can be used as "standard candles"—objects of known intrinsic brightness—to measure the expansion of the universe with high precision. Combined observations from a variety of telescopes show that the expansion of the universe is accelerating. What drives that acceleration goes by the mysterious moniker - dark energy - its name reflecting the profound mysteries still surrounding the phenomena.
Gemini's ability to obtain spectra of exceptionally faint supernovae (Figure 1) is due, in part, to a technique called Nod and Shuffle (N&S). Figure 2 plots corrected absolute brightness against supernova redshift, with the shape of the plot being the signal of the existence of dark energy. Astronomers used the Gemini telescopes in Chile and Hawai'i to obtain many of the observations in Figure 2, mostly on the right side of the plot, where supernovae are fainter and more distant. According to Isobel Hook, team member for the SNLS, “Gemini’s key role was to provide spectroscopic redshifts and classification of the SN types for the most distant (hence faintest) supernovae candidates. The N&S mode on GMOS made this possible by greatly reducing systematic effects associated with sky subtraction."
The Supernova Legacy Survey is the single largest program ever executed by Gemini with over 600 hours allocated over seven semesters. The ESSENCE program was also very large, using over 350 hours of Gemini time, and reporting results in some of the most-cited publications based on Gemini data. Observations for both surveys extensively used multiple facilities, including telescopes at the Cerro Tololo Inter-American Observatory, the Canada-France-Hawaii Telescope, the United Kingdom Infrared Telescope, the W.M. Keck Observatory, the Magellan Telescope, the Very Large Telescope, and the Hubble Space Telescope.
Gemini Observatory staff look forward to continuing exciting research in this area as the current generation of 8- to 10-meter-class telescopes capture the light from distant galaxies to further our understanding of dark energy. Gemini is proud to play a role in understanding these fundamental questions of our universe by providing the facilities for our research community to use. It is the imagination and creativity of our users that allow such understanding to be realized and nowhere is this better illustrated than with the 2011 Nobel Prize for Physics.