November 2, 2009
Precise Picture Of Early Universe Supports ‘Dark Matter’ Theory
A detailed picture of the seeds of structures in the universe has been unveiled by an international team co-led by a Cardiff University scientist.
The team has obtained extremely precise data about the early universe, using a telescope near the South Pole in the Antarctic.Their measurements of the cosmic microwave background - a faintly glowing relic of the hot, dense, young universe - provide further support for the standard cosmological model of the universe. The findings confirm the model's prediction that dark matter and dark energy make up 95% of everything in existence, while ordinary matter makes up just 5%.
In a paper published in the November 1 issue of The Astrophysical Journal, researchers on the QUaD telescope project have released detailed maps of the cosmic microwave background (CMB). The researchers focused their measurements on variations in the CMB's temperature and polarization to learn about the distribution of matter in the early universe. Polarization is the direction in which vibrations travel from all light rays, which is at right angles to the ray's direction of travel.
The light from the early universe was initially unpolarized but became polarized when it struck moving matter in the very early universe. By creating maps of this polarization, the QUaD team was able to investigate not just where the matter existed, but also how it was moving. The results very closely match the temperature and polarization predicted by the existence of dark matter and dark energy in the standard cosmological model.
The team was jointly led by Professor Walter Gear, Head of the School of Physics and astronomy at Cardiff University and Professor Sarah Church of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), jointly located at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University.
Professor Gear said: "Studying the CMB radiation has given us extremely precise pictures of the Universe at just 400,000 years old. When we first started working on this project the polarization of the CMB hadn't even been detected and we thought we might be able to find something wrong with the theory. The fact that these superb data fit the theory so beautifully is in many ways even more amazing. This reinforces the view that researchers are on the right track and need to learn more about the strange nature of dark energy and dark matter if we are to fully understand the workings of the universe."
Michael Brown, of the Kavli Institute for Cosmology at the University of Cambridge, lead author of the new study added: "With these new QUaD measurements, we have tested further our standard model of the Universe. Reassuringly, the model has passed this test remarkably well."
Professor Sarah Church, Deputy Director of KIPAC, said: "When I first started in this field, some people were adamant that they understood the contents of the universe quite well. But that understanding was shattered when evidence for dark energy was discovered. Now that we again feel we have a very good understanding of what makes up the universe, it's extremely important for us to amass strong evidence using many different measurement techniques that this model is correct, so that this doesn't happen again."
The QUaD (QUEST at DASI) project utilizes the Q U Extra-galactic Survey Telescope (QUEST) instrument at the South Pole that was installed on the mechanical structure from a previous experiment called DASI (Degree Angular Scale Interferometer).
The principal members of the QUaD collaboration are Cardiff University (United Kingdom), the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University and the Department of Energy's SLAC National Accelerator Laboratory, the Kavli Institute for Cosmological Physics at the University of Chicago, the California Institute of Technology, the Jet Propulsion Laboratory, Cambridge University (United Kingdom), University of Edinburgh (United Kingdom) and Maynooth College (Ireland).
The Science and Technology Facilities Council (formerly the Particle Physics and Astronomy Research Council ) funded the U.K portion of the research. The National Science Foundation funded the U.S. portion of the experiment, and Research and Enterprise Ireland funded the Irish contribution.
The Standard Model of the cosmos
Although successful, the standard model of the cosmos is also rather absurd - it proposes that the Universe is dominated by two components, neither of which we can see directly. The first is dark matter, an entirely new kind of matter that appears to suffuse our galaxy (and others) without interacting with the ordinary matter of which stars, planets, and humans are made. The second component is even more mysterious - a strange substance known as "dark energy"- energy of empty space itself. The presence of dark energy means that the Universe is not just expanding, but that the expansion is accelerating. The exact nature of dark energy is unknown, but it is possible that the acceleration will continue until "“ albeit many billions of years in the future "“ it rips the Universe apart.
Image Caption: The QUaD collaboration uses the 2.6m telescope shown here to view the temperature and polarization of the cosmic microwave background, a faintly glowing relic of the hot, dense, young universe. Credit: Cardiff University
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