Almost perfect

Print edition : May 03, 2013

Figure 1: The Cosmic Microwave Background, or CMB, as seen by ESA's Planck satellite (upper right half) and by its predecessor, NASA's Wilkinson Microwave Anisotopy Probe (lower left half). With greater resolution and sensitivity over nine frequency channels, Planck has delivered the most precise image so far of the CMB. Photo: ESA

Figure 2: Planck's high-precision CMB map has allowed scientists to extract the most refined values yet of the universe's ingredients. The 'before Planck' figure is based on the WMAP's nine-year data.

Figure 3: This graph shows the temperature fluctuations in the Cosmic Microwave Background detected by Planck at different angular scales on the sky, starting at ninety degrees on the left side of the graph through to the smallest scales on the right hand side.The red dots are measurements made with Planck; these are shown with error bars. The green curve represents the best fit of the 'standard model of cosmology' to the Planck data. The pale green area around the curve shows the predictions of all the variations of the standard model that best agree with the data.While the observations on small and intermediate angular scales agree extremely well with the model predictions, the fluctuations detected on large angular scales on the sky – between 90 and six degrees – are about 10 per cent weaker than the best fit of the standard model to Planck data.

Figure 4: Two CMB anomalous features hinted at by Planck’s predecessor, NASA’s WMAP, are confirmed in the new high-precision data. One is an asymmetry in the average temperatures on opposite hemispheres of the sky (indicated by the curved line), with slightly higher average temperatures in the southern ecliptic hemisphere and slightly lower average temperatures in the northern ecliptic hemisphere. This runs counter to the prediction made by the standard model that the universe should be broadly similar in any direction we look. There is also a cold spot that extends over a patch of sky that is much larger than expected (circled). In this image the anomalous regions have been enhanced with red and blue shading to make them more clearly visible. Photo: ESA

The precise picture delivered by Planck conforms most spectacularly to the expectations of the Standard Model of the universe, but the evidence of anomalous features also indicates that something fundamental may be missing from the standard framework.

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