Dark energy may be vacuumJanuary 17, 2007Researchers at the University of Copenhagen's Dark Cosmology Centre at the Niels Bohr Institute have brought us one step closer to understanding what the universe is made of. As part of the international collaboration ESSENCE they have observed distant supernovae (exploding stars), some of which emitted the light we now see more than half the age of the universe ago. Using these supernovae they have traced the expansion history of the universe with unprecedented accuracy and sharpened our knowledge of what it might be that is causing the mysterious acceleration of the expansion of the universe. Background and outline At the end of last century astronomers discovered the startling fact that the expansion of our universe is not slowing down, as all our previous understanding of gravity had predicted. Rather the expansion is speeding up. Nothing in conventional physics can explain such a result. It means that either the universe is made up of around 70% 'dark energy' (something that has a sort of anti-gravity) or our theory of gravity is flawed.
Now, as part of the international collaboration "ESSENCE", researchers at the Danish Dark Cosmology Centre have added a new piece to the puzzle. In two papers recently released they detail observations of supernovae (exploding stars) that allow them to trace the expansion history of the universe in unprecedented detail. ESSENCE is an extension of the original team that discovered the acceleration of the universe and these results push the limits of technology and knowledge, observing light from dying stars that was emitted almost half the age of the universe ago. In a third paper, led by the Danish team and released this week, the many new theories that have been proposed to explain the acceleration of the universe are critically assessed in the face of this new data. Dr. Jesper Sollerman and Dr. Tamara Davis lead the team who show that despite the increased sophistication in cosmological models over the last century the best model to explain the acceleration remains one that was proposed by Einstein back in 1917. Although Einstein's reasoning at the time was flawed (he proposed the modification to his theory so it could support a static universe, because in those days everyone 'knew' the universe was not expanding, it may be that he was right all along. Scientific details: The results include 60 new type Ia supernovae discovered on the Cerro-Tololo Interamerican Observatory 4m telescope in an ongoing survey that so far has lasted four years. In order to follow up these discoveries the team uses some of the biggest telescopes in the world: the 8.2m VLT (Very Large Telescope) run by the European Southern Observatory and the 6m Magellan telescope (both in Chile), the 8m Keck telescope and the 10m Gemini telescope (both in Hawaii). The ESSENCE team includes 38 top researchers from many different countries on four continents. The primary aim of the experiment is to measure the 'dark energy'-the thing that is causing the acceleration of the universe-to better than 10%. The feature of this dark energy that we measure is its 'equation of state'. This also allows us to check whether our theory of gravity needs modification. So far it looks like our theory is correct and that the strange acceleration of the expansion of the universe can be explained by Einstein's 'cosmological constant'. In modern terms the cosmological constant is viewed as a quantum mechanical phenomenon called the 'energy of the vacuum'. In other words, the energy of empty space. It is this energy that is causing the universe to accelerate. The new data shows that none of the fancy new theories that have been proposed in the last decade are necessary to explain the acceleration. Rather, vacuum energy is the most likely cause and the expansion history of the universe can be explained by simply adding this constant background of acceleration into the normal theory of gravity. University of Copenhagen Science News and Science Current Events Tag Cloud This tag cloud is a visual representation of term frequencies of random science news topics with common terms grouped together and emphasized by their display size. Child Abuse Radiofrequency Ablation Lung Disease Miscarriage Evolution Reproduction Tonsillectomy Biodiversity Multiple Sclerosis Contraception Deforestation Fruit Fly Statin Sexual Selection Ice Sheet HIV Neuroblastoma Jupiter Neurons Bioenergy Endothelial Cells Biomarkers Autoimmune Disease Cloning Whooping cough
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Related Dark Energy Current Events and Dark Energy News Articles Radio telescopes extend astronomy's best 'yardstick' Radio astronomers have directly measured the distance to a faraway galaxy, providing a valuable "yardstick" for calibrating large astronomical distances and demonstrating a vital method that could help determine the elusive nature of the mysterious Dark Energy that pervades the Universe. Cosmology's Best Standard Candles Get Even Better Members of the international Nearby Supernova Factory (SNfactory), a collaboration among the U.S. Department of Energy's Lawrence Berkeley National Laboratory, a consortium of French laboratories, and Yale University, have found a new technique that establishes the intrinsic brightness of Type Ia supernovae more accurately than ever before. Astronomy's bright future To mark UNESCO's International Year of Astronomy (IYA2009), six leading astronomers from the UK, the US, Europe and Asia write in March's Physics World about the biggest challenges and opportunities facing international astronomers over the next couple of decades. Colors of Quasars Reveal a Dusty Universe The vast expanses of intergalactic space appear to be filled with a haze of tiny, smoke-like "dust" particles that dim the light from distant objects and subtly change their colors, according to a team of astronomers from the Sloan Digital Sky Survey (SDSS-II). Cosmologists aim to observe first moments of universe During the next decade, a delicate measurement of primordial light could reveal convincing evidence for the popular cosmic inflation theory, which proposes that a random, microscopic density fluctuation in the fabric of space and time gave birth to the universe in a hot big bang approximately 13.7 billion years ago. Earth not center of the universe, surrounded by 'dark energy': UBC cosmologists Earth's location in the Universe is utterly unremarkable, despite recent theories that propose toppling a foundation of modern cosmology, according to a team of University of British Columbia researchers. Throwing light on the dark side of the Universe Although we may believe humans know a lot about the Universe, there are still a lot of phenomena to be explained. A team of cosmologists from the University of the Basque Country are searching for the model that best explains the evolution of the Universe. Ghostly glow reveals galaxy clusters in collision A team of scientists, including astronomers from the Naval Research Laboratory (NRL), have detected long wavelength radio emission from a colliding, massive galaxy cluster which, surprisingly, is not detected at the shorter wavelengths typically seen in these objects. Spallation Neutron Source sends first neutrons to 'Big Bang' beam line New analytical tools coming on line at the Spallation Neutron Source, the Department of Energy's state-of-the-art neutron science facility at Oak Ridge National Laboratory, include a beam line dedicated to nuclear physics studies. Scientists Detect Cosmic 'Dark Flow' Across Billions of Light Years Using data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP), scientists have identified an unexpected motion in distant galaxy clusters. The cause, they suggest, is the gravitational attraction of matter that lies beyond the observable universe. More Dark Energy Current Events and Dark Energy News Articles |
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