Artist’s poster of the Planck satellite

ESA’s Planck satellite will observe the cosmic microwave background (CMB), the radiation released into the Universe shortly after the Big Bang, about 14 thousand million years ago, when the first light started to travel freely in space. From that time, what was once a searing fireball has cooled to become a background sea of microwaves.
Planck will measure the temperature variations across this microwave background with much better sensitivity, angular resolution and frequency range than any previous satellite. The combination of these factors will give astronomers an unprecedented view of our Universe when it was extremely young: just 380 000 years old.