Who mapped the world

Planck completes mapping of the microwave background

Orsay (France) - Mission completed successfully: Last weekend, the high-frequency instrument on board the European astronomy satellite Planck stopped working after the liquid helium used as a coolant was used up as planned. Planck is creating the most accurate map of cosmic background radiation to date, the radiation echo of the Big Bang 13.7 billion years ago. The astronomers hope for new knowledge about the formation and the early days of the universe.

“We received better data than we expected from the mission,” says Jean-Loup Puget from the Université Paris Sud in Orsay, the chief scientist of the high-frequency instrument of the Planck mission. The observatory, which was launched in May 2009, was originally intended to cover the entire sky twice. But Planck worked flawlessly for thirty months and even managed five complete scans of the sky. A second device on board Planck, the low-frequency instrument, can continue to carry out measurements for several months, which are useful for calibrating the high-frequency data and thus further improve the quality of the results.

Four hundred thousand years after the Big Bang, the cosmos had cooled down to four thousand degrees and suddenly became transparent to electromagnetic radiation. The expansion of space has cooled the radiation released at that time over the course of billions of years to 2.7 degrees above absolute zero today. Tiny temperature fluctuations in this background radiation provide astronomers with information about the formation of the first structures in the universe, about the matter and energy content of the cosmos and about the exact course of the Big Bang. The researchers hope that the map of the background radiation provided by Planck is at least three times more accurate than the best data to date that the American satellite WMAP transmitted to Earth from 2001 to 2010.

Now the researchers involved in the mission have to laboriously eliminate all disturbances - such as the foreground radiation of the Milky Way - from the data. Puget estimates that it will take at least a year to evaluate the data. The results are eagerly awaited by astrophysicists all over the world, because there are still numerous competing theories about the origin of the cosmos. "Planck's data will throw entire families of these models out of the running," says Puget, "we just don't know which ones."