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Story of the Universe

Planck: ESA’s mission to map the afterglow from the Big Bang

Artist's impression of Planck
Artist's impression of Planck

23 October 2013
After more than 4 years of scanning the sky to look back to the beginning of time, the mission of ESA’s Planck observatory has come to an end.

Planck was designed to investigate one of the greatest mysteries in science - what happened when the Universe was born. Scientists believe it suddenly expanded outward in an event known as the Big Bang. Unfortunately, none of our telescopes can see that far back in time. However, Planck was able to detect tiny temperature fluctuations in the cosmic microwave background - the first light emitted after the Big Bang took place.

Planck was launched together with ESA’s Herschel infrared observatory on 14 May 2009 and was placed in a special orbit 1.5 million km from Earth. On board were two sensitive instruments that could scan the entire sky to detect extremely faint microwave signals from the beginning of time. One of these instruments completed its survey in January 2012, but the other one continued to operate until 3 October 2013.

The anisotropies of the Cosmic microwave background (CMB) as obs
The Cosmic microwave background (CMB) as observed by Planck

After travelling for billions of years across the Universe, the afterglow of the Big Bang was detected by Planck. The 2 tonne spacecraft provided the most accurate and detailed map ever made of the first light in the Universe, revealing new information about its age, distribution and origins.

By mapping the afterglow of the Big Bang, Planck has provided a snapshot of the Universe 370,000 years after it was born. Its maps show that the cosmic microwave background is spread remarkably evenly over the entire sky. Nevertheless, some tiny variations are visible, indicating the “seeds” where matter collected. These eventually grew into the first stars and galaxies.

The data suggest that the Universe is expanding a little slower than scientists thought. It is 13.8 billion years old, 100 million years older than previous estimates. The data also show there is less dark energy, but more normal and dark matter in the Universe than previously believed. Dark matter is an invisible substance that can only be detected through the effects of its gravity, while dark energy is pushing our Universe apart. The nature of both remains unknown.

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