The Planck satellite was launched in 2009 by the European Space Agency. The Observatory made important contributions to this satellite, which functioned until 2013. Its purpose was to study in detail the fossil radiation of the Universe, which was radiated roughly 400,000 years after the Big Bang and has taken almost 14 billion years to reach us. It was made up of a 1.5 m diameter telescope, cooled to a temperature close to absolute zero. The whole sky was observed with unequalled sensitivity; thanks to Planck it has been possible to reconstruct what happened after the Big Bang and to check the theories concerning the structure of the Universe. It has also furnished the best image of the distribution of interstellar material in the Milky Way.
