CERN Courier May 2013 Astrowatch

C OMPILED BY M ARC TÜRLER , ISDC AND O BSERVATORY OF THE U NIVERSITY OF G ENEVA Planck reveals an almost perfect

The long awaited results from ESA’s Planck mission, based on the detailed observations to date of the cosmic microwave background (CMB), were released on 21 March. While the new data confi rm to high precision the standard model of , the detection of several anomalies could be hints of new physics to be understood. ESA’s Planck and Herschel missions were launched simultaneously by an rocket on 14 May 2009 (CERN Courier July/August 2009 p6). Since then, Planck An has been scanning the whole sky every six analysis anomalies months. After the results on galactic and of this all-sky seen by extragalactic foregrounds (CERN Courier map of the cosmic WMAP, such as a April 2012 p15), the Planck collaboration microwave background as lack of power in fl uctuations at has now released the CMB results, the prime measured by the Planck satellite allows the large angular scales, a small asymmetry scientifi c objective of the mission. The derivation of the fundamental cosmological on both sides of the ecliptic plane and collaboration issued almost 30 publications parameters governing the history and the fate the WMAP spot (CERN Courier simultaneously, together with the data from of the universe. Colours indicate slight October 2007 p13). Planck shows that these the fi rst half of the mission (15.5 months). differences in temperature. (Image credit: anomalies are, indeed, of cosmic origin but The CMB is a snapshot of the universe ESA and the Planck collaboration.) they are at a level still marginally compatible when it was 380,000 years old. At that (2–3σ) with statistical variations on the sky. time, the young universe was fi lled with a The main highlights of the Planck results hot, dense medium of interacting protons, are constraints on the number and mass

and photons at about 2700° C. of relativistic (Neff = 3.30±0.27 When the protons and electrons combined to and Σmν < 0.66 eV), a strong constraint form hydrogen atoms, radiation was set free. on any primordial non-Gaussianity As the universe expanded, this radiation was (fNL = 2.7±5.8) and constraints on infl ation stretched to microwave wavelengths, today models (ns = 0.96±0.01 and r < 0.11 at 95% equivalent to a temperature of just 2.7° C CL). In addition to the CMB data, Planck above . The CMB is extremely is also releasing new catalogues of galaxy uniform all over the sky. There are only clusters and compact sources. This yields a tiny temperature fl uctuations (at a level of The Planck spacecraft. (Image credit: ESA/ potentially interesting tension between the 10 –5) that correspond to regions of slightly Image by AOES Medialab.) amplitude of fl uctuations derived different densities at very early times. from the CMB (σ8 = 0.82±0.02) and from Gravity will have acted to increase these confi rmation of the standardΛ CDM model galaxy clusters (σ8 = 0.77±0.02). Possibly fl uctuations to form the galaxies and galaxy of the universe. the most unexpected result is a precise clusters that are seen today. Compared with NASA’s Wilkinson determination of the famous Hubble The fl uctuations are of different amplitude Microwave Anisotropy Probe (WMAP) constant, which describes the rate of on different angular scales. This is described satellite, Planck has a much higher expansion of the universe, at a signifi cantly by the power spectrum derived from the sensitivity, a smaller angular scale and a lower value (H0 = 67.9±1.5 km/s/Mpc) than all-sky map of the CMB. The observed shape larger spectral coverage, with nine bands derived by other means. This was one of of the power spectrum can then be fi tted by instead of fi ve. Yet despite this, Planck has the prime objectives of the Hubble Space a model curve, whose shape is controlled not been able to change fundamentally the Telescope; now it is Planck that makes the by a set of cosmological parameters. view of the cosmos as derived by WMAP most precise determination so far. The There are only six free parameters for (CERN Courier May 2006 p12, May 2008 next milestone for Planck will be in 2014 the standard model of a fl at universe with p8). The updated energy-density content with the release of the fi nal products for the cold and a cosmological of the present universe consists of slightly complete mission, including the constant, ΛCDM. Possible deviations from higher fractions of ordinary, baryonic matter measurements. There is still potential for a pure ΛCDM cosmology can be tested by (4.9% instead of 4.5%) and of dark matter more exotic discoveries. freeing additional parameters of the model. (26.8% instead of 22.7%), compensated by All attempts to search for deviations in the a decrease in the fraction of ● Further reading Planck data have proved insignifi cant. The (68.3% instead of 72.8%). Planck has also Planck collaboration 2013 arXiv: 1303.5062. main result of Planck is thus a remarkable confi rmed the existence of some large-scale [-ph.CO].

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Untitled-2 1 09/04/2013 11:32 CERNCOURIER www. V o l u m e 5 3 N u m b e r 4 M a y 2 0 1 3 CERN Courier May 2013 Astrowatch

C OMPILED BY M ARC TÜRLER , ISDC AND O BSERVATORY OF THE U NIVERSITY OF G ENEVA Planck reveals an almost perfect universe

The long awaited results from ESA’s Planck mission, based on the most detailed observations to date of the cosmic microwave background (CMB), were released on 21 March. While the new data confi rm to high precision the standard model of cosmology, the detection of several anomalies could be hints of new physics to be understood. ESA’s Planck and Herschel missions were launched simultaneously by an Ariane 5 rocket on 14 May 2009 (CERN Courier July/August 2009 p6). Since then, Planck An has been scanning the whole sky every six analysis anomalies months. After the results on galactic and of this all-sky seen by extragalactic foregrounds (CERN Courier map of the cosmic WMAP, such as a April 2012 p15), the Planck collaboration microwave background as lack of power in fl uctuations at has now released the CMB results, the prime measured by the Planck satellite allows the large angular scales, a small asymmetry scientifi c objective of the mission. The derivation of the fundamental cosmological on both sides of the ecliptic plane and collaboration issued almost 30 publications parameters governing the history and the fate the WMAP cold spot (CERN Courier simultaneously, together with the data from of the universe. Colours indicate slight October 2007 p13). Planck shows that these the fi rst half of the mission (15.5 months). differences in temperature. (Image credit: anomalies are, indeed, of cosmic origin but The CMB is a snapshot of the universe ESA and the Planck collaboration.) they are at a level still marginally compatible when it was 380,000 years old. At that (2–3σ) with statistical variations on the sky. time, the young universe was fi lled with a The main highlights of the Planck results hot, dense medium of interacting protons, are constraints on the number and mass

electrons and photons at about 2700° C. of relativistic neutrinos (Neff = 3.30±0.27 When the protons and electrons combined to and Σmν < 0.66 eV), a strong constraint form hydrogen atoms, radiation was set free. on any primordial non-Gaussianity As the universe expanded, this radiation was (fNL = 2.7±5.8) and constraints on infl ation stretched to microwave wavelengths, today models (ns = 0.96±0.01 and r < 0.11 at 95% equivalent to a temperature of just 2.7° C CL). In addition to the CMB data, Planck above absolute zero. The CMB is extremely is also releasing new catalogues of galaxy uniform all over the sky. There are only clusters and compact sources. This yields a tiny temperature fl uctuations (at a level of The Planck spacecraft. (Image credit: ESA/ potentially interesting tension between the 10 –5) that correspond to regions of slightly Image by AOES Medialab.) amplitude of matter fl uctuations derived different densities at very early times. from the CMB (σ8 = 0.82±0.02) and from Gravity will have acted to increase these confi rmation of the standardΛ CDM model galaxy clusters (σ8 = 0.77±0.02). Possibly fl uctuations to form the galaxies and galaxy of the universe. the most unexpected result is a precise clusters that are seen today. Compared with NASA’s Wilkinson determination of the famous Hubble The fl uctuations are of different amplitude Microwave Anisotropy Probe (WMAP) constant, which describes the rate of on different angular scales. This is described satellite, Planck has a much higher expansion of the universe, at a signifi cantly by the power spectrum derived from the sensitivity, a smaller angular scale and a lower value (H0 = 67.9±1.5 km/s/Mpc) than all-sky map of the CMB. The observed shape larger spectral coverage, with nine bands derived by other means. This was one of of the power spectrum can then be fi tted by instead of fi ve. Yet despite this, Planck has the prime objectives of the Hubble Space a model curve, whose shape is controlled not been able to change fundamentally the Telescope; now it is Planck that makes the by a set of cosmological parameters. view of the cosmos as derived by WMAP most precise determination so far. The There are only six free parameters for (CERN Courier May 2006 p12, May 2008 next milestone for Planck will be in 2014 the standard model of a fl at universe with p8). The updated energy-density content with the release of the fi nal products for the cold dark matter and a cosmological of the present universe consists of slightly complete mission, including the polarization constant, ΛCDM. Possible deviations from higher fractions of ordinary, baryonic matter measurements. There is still potential for a pure ΛCDM cosmology can be tested by (4.9% instead of 4.5%) and of dark matter more exotic discoveries. freeing additional parameters of the model. (26.8% instead of 22.7%), compensated by All attempts to search for deviations in the a decrease in the fraction of dark energy ● Further reading Planck data have proved insignifi cant. The (68.3% instead of 72.8%). Planck has also Planck collaboration 2013 arXiv: 1303.5062. main result of Planck is thus a remarkable confi rmed the existence of some large-scale [astron-ph.CO].

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Untitled-2 1 09/04/2013 11:32 CERNCOURIER www. V o l u m e 5 3 N u m b e r 4 M a y 2 0 1 3