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According to the Big Bang model, there was a lot of light in the primordial Universe. While this light has been greatly diluted as the Universe expanded, it can still be detected by surveying the skies. The remnants of this first light, called the cosmic microwave background (CMB), were analysed from May 2009 to October 2013 by the Planck satellite, allowing astrophysicists to take a ‘snapshot’ of the Universe as it was just 380,000 years after the Big Bang and learn more about its birth and the formation of galaxies.
To observe this fossil radiation, Planck used its 1.5-metre-diameter telescope and two instruments: LFI (Low Frequency Instrument) and HFI (High Frequency Instrument), the latter operating in the submillimetre range of the spectrum where very cold objects emit. CNES was involved in the Planck astronomy mission via its contribution to ESA’s mandatory scientific programme and through its participation in developing the HFI instrument, led by French science teams, and its data processing centre.