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Nature 04457.txt

#Planck snaps infant Universe For astronomers, it is the ultimate treasure map. On 21 march, the Planck space telescope team released the highest-precision map yet of the cosmic microwave background (CMB), the faint but ubiquitous afterglow of the Big bang. Crowning nearly 50 years of CMB study, the map records the precise contours of the nascent Universe #and in doing so pins down key parameters of the Universe today. The tiny fluctuations embedded in the CMB map reveal a Universe that is expanding slightly more slowly than had been thought. That dials back the amount of gravity-countering dark energy to 68.3%of the Universe and adds a little more unseen dark matter to the mix. It also means that the Universe is a little older: 13.82 billion years old, adding a few tens of millions of years to the previously calculated value. The map even shows that the number of neutrino flavours permeating the cosmos will probably remain at three#had there been a fourth, the Universe would have expanded more quickly during its first moments. These results represent refinements of numbers obtained by previous missions such as the Wilkinson Microwave Anisotropy Probe (WMAP. Where the Planck spacecraft, watching the sky from a vantage point 1. 5#million kilometres away, breaks the most new ground is in its support for the reigning theory that describes the instant after the Big bang. The theory, known as inflation, holds that during an unimaginably rapid expansion lasting just 10##32#seconds or so, the Universe grew from a subatomic point to something the size of a grapefruit that then continued to expand at a more stately pace. This growth spurt would help to explain why the Universe we see today is homogeneous on the largest scales yet riddled with clumps, filaments and sheets of galaxies.""Planck could have found that there was something majorly wrong with inflation, says astrophysicist Jo Dunkley at the University of Oxford, UK, who has worked on data from Planck and the WMAP.""Instead, we ve got new evidence that this expansion did happen. In the minutes that followed the burst of inflation, particles such as protons and electrons formed from the cauldron of proto-matter, and photons began to bounce around like pinballs. It was only 380,000#years later, when the charged plasma cooled into neutral atoms, that those photons could fly freely. Today they make up the CMB, and carry with them an imprint of the quantum fluctuations that roiled the inflationary Universe. Seen in the map as tiny variations around an average temperature of 2. 7 kelvins the fluctuations caused alterations in the density of matter, which ultimately snowballed into the galaxies seen today.""All the structures we see in the Universe are coming from these little perturbations, says Paul Shellard, a Planck cosmologist at the University of Cambridge, UK. SLIDESHOW: Homing in on the cosmic microwave background In 1965, Arno Penzias and Robert Wilson discovered the cosmic microwave background. Their giant but crude microwave receiver saw the radiation as being the same in all directions, occurring at 2. 7 kelvin. NASA/WMAP SCIENCE TEAMIT was not until the launch of the Cosmic Background Explorer (COBE) spacecraft that astronomers could begin to see variations in the background, at levels of 1 part in 100,000. NASATHE Wilkinson Microwave Anisotropy Probe, launched in 2001, improved on COBE by looking for such anisotropy at much smaller angular scales. NASA/WMAP SCIENCE TEAMPLANCK launched in 2009, provides a capstone to the study of the cosmic microwave background. But unambiguous confirmation of a cosmic burst of expansion known as inflation remains elusive. ES a

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