An important milestone has been reached in the quest for detecting the mysterious Dark Energy component of our Universe with the development of one of the largest imaging systems in the world, which comprises five lenses and a 500 megapixel camera.
Our current understanding of the nature and composition of the Universe is that roughly four percent is made up of ‘ordinary’ baryonic matter (that is, all atomic matter) and 22 percent comprises Dark Matter, leaving 74 percent unaccounted for, the so-called Dark Energy, which is thought to drive the accelerating expansion of the Universe.
An aerial image of the National Optical Astronomy Observatory’s Cerro Tololo Inter-American Observatory in Chile. The largest dome is home to the Blanco 4-metre telescope, which will be play host to the Dark Energy Survey. Image: NOAO/AURA/NSF.
Scientists are laying their hopes of producing accurate maps of this illusive Dark Energy on the next generation sky survey, the Dark Energy Survey (DES) camera, which will map an astounding 300 million galaxies using the Blanco four-metre telescope at Chile’s Cerro Tololo Inter-American Observatory. DES will make use of an extremely red-sensitive 500 megapixel camera, a one-metre, 2.2 degree field of view prime focus corrector, and a data acquisition system fast enough to take images in 17 seconds.
"Dark Energy is one of the biggest puzzles in the whole of physics, going back to a concept proposed by Einstein 90 years ago,” says Professor Ofer Lahav, head of University College London’s (UCL) Astrophysics Group. “The DES observations will tell us if Einstein was right or if we need a major shift in our understanding of the Universe."
The glass for the five lenses – the largest of which is one metre in diameter – was manufactured in the United States before being shipped to France where the lenses will now be polished to a smoothness level of one millionth of a centimetre.
"The polishing and assembly of the five DES lenses will be a major technological achievement, producing one of the largest cameras on Earth," says Dr Peter Doel of the Optical Science Laboratory at UCL.
The lenses will then be sent to the Optical Science Laboratory at UCL for assembly into the camera, and from there to the telescope in Chile where observations are expected to start in 2011 and continue through to 2016. The team hope to extract cosmological information from the Dark Energy through a number of techniques, including counting the spatial distribution of galaxies at different photometric redshifts and by studying thousands of supernova.
The Dark Energy Survey will map the positions of millions of galaxies by looking at galaxy clustering, counts of galaxy clusters, weak gravitational lensing, and thousands of supernovae. "Each of the techniques will measure the dark energy in a different way, broadly speaking via measuring the geometry of the Universe and the growth of cosmic structure," Professor Lahav tells Astronomy Now. "By combining the four methods we can achieve better estimates of the dark energy parameters."