Jeudi 11 avril 2013
Sketched out in 1992, selected by ESA in 1996, launched in 2009, Planck will have delivered on
March 21st its first full sky maps of the millimetric emission at 9 frequencies, as well as those
which follow from them, and in particular Planck map of the anisotropies of the Cosmic Microwave
Background (CMB). The later displays minuscule variations as a function of the observing
direction of the temperature of the fossile radiation around its mean temperature of 2.725K. I will
briefly describe how these high resolution maps with a precision of a few parts in a million have
been obtained, from collection to analysis of the first 500 billion samples of our HFI instrument.
CMB anisotropies reveal the imprint of the primordial fluctuations which initiate the growth of the
large scale structures of the Universe, as transformed by their evolution, in particular during the
first 370 000 years, i.e. till the Universe became transparent and the forming of the image we
record today. The statistical characteristics of these anisotropies allow constraining jointly the
physics of the creation of the primordial fluctuations and that of their evolution. They teach us the
possible value of the parameters of the models which we confront to data. I will describe Planck
estimates of the density of the constituents of the Universe (usual matter, cold dark matter or
CDM, dark energy...), and their implication in terms of derived quantities like the expansion rate or
the spatial curvature. I will review what we learnt on the generation of the fluctuation, and wil
discuss extensions of the standard cosmological model, so called "Lambda-CDM", both in term of
non minimal physical models — multi-field inflation for instance, or additional constituents - like
cosmic strings or a fourth neutrino.
Finally, I will briefly describe other promising results on the matter distribution which is travelled
through by the CMB image on its long 13.7 billion years trip towards us. I will mention in particular
what we can learn on the dark matter distribution - which is detected through its distorting effet of
the CMB image by gravitationnal lensing, or that of hot gaz, which is revealed by the spectral
distortion it induces.
This seminar will be introduced by Professor Viatcheslav Mukhanov who will put these
results in perspective.