|
After a decade of construction and eight years of operation, the Sloan Digital Sky Survey (SDSS) completed its observations in mid-July and will release its final data set to the public in October. SDSS-III, a six-year program composed of four new surveys, has now begun, using the same telescope. "I'm glad we didn't know at the beginning how hard it would be and how long it would take," said SDSS Project Scientist Jim Gunn, the Princeton astronomer who has guided the project since its inception. "But now that we've finally accomplished what we set out to do, and much more besides, it seems worth all the effort and all the headaches along the way." The Institute of Cosmology and Gravitation (ICG) at the University of Portsmouth has been a member of the SDSS since 2004, and Jim Gunn was given an honorary doctorate by UoP in 2005. The universities of Portsmouth and Cambridge are the only UK institutes that are members of the new SDSS-III project. Using a 2.5-metre diameter telescope equipped with two specialized instruments -- a 125-Megapixel digital camera and spectrographs that observe 640 stars and galaxies at a time -- the SDSS has completed its original goals by making deep, multi-colour images covering more than one-quarter of the sky and measuring the distances to nearly one million galaxies and over 100,000 quasars, thus creating the largest ever 3-dimensional maps of cosmic structure. "What is amazing is the huge range of the discoveries that have come from SDSS data," said ProfessorBob Nichol, the leader of the ICG's involvement in SDSS, and himself one of the founding members of the SDSS. "We designed it primarily as a survey to map the distribution of galaxies and quasars, but it's also had a huge impact on the study of the Universe, in particular on our understanding of Dark Energy." Dark Energy is the mysterious field - or possibly an unknown property of gravity - that is causing the galaxies to accelerate away from each other, instead of moving apart at a slower rate, as was expected. The achievements of the SDSS were celebrated 16-17 August an international symposium titled "The Sloan Digital Sky Survey: Asteroids to Cosmology," hosted by the Kavli Institute for Cosmological Physics at the University of Chicago. In more than 80 presentations, astronomers from around the globe will describe new discoveries about stars, galaxies, and the cosmos, from the SDSS and from some of the other ambitious surveys that it helped inspire. SDSS-II observations ended on July 14. On July 15, SDSS-III began. "The ability of the SDSS facility to simultaneously measure spectra of hundreds of objects over a wide area of sky remains a powerful tool for astronomy," said SDSS-III Director Daniel Eisenstein, an astronomer at the University of Arizona. SDSS-III is a set of four ambitious new spectrosopic surveys, addressing a wide range of scientific questions. The biggest of the four surveys - BOSS - will use a novel technique to study the properties of dark energy. Portsmouth is actively involved in BOSS. "Sound waves that travel in the early universe imprint a characteristic scale on the distribution of galaxies, which was detected by the SDSS," says Dr Will Percival of the ICG, who is a leading expert on this new technique. "We can use this scale as a 'standard ruler' to measure how fast the Universe is accelerating". News Source: www.port.ac.uk |
