Illustration: ESA

Prize completes historical mapping of the universe

Tuesday 28 Aug 18


Hans Ulrik Nørgaard-Nielsen
Senior Scientist
DTU Space
+45 45 25 97 28

The Planck mission

Launched into space on 14 May 2009, the Planck mission was successfully placed at a distance of 1.5 million kilometres from Earth—approximately four times further away than the moon.

The mission in space was completed in 2013. The last data set based on Planck data was released in 2018.

Planck is a joint European project under the European Space Agency, ESA. The Planck satellite is 4.2 metres long and weighs 1,900 kg. It rotates and in this way scans all of space for the cosmic microwave background (CMB), which is ‘remnants’ or signatures of light from the Big Bang.

Data from Planck has been utilized to produce a map of the distribution of heat in the early universe.

DTU has supplied the satellite’s two mirrors and has participated in the research based on the data collected.

Researchers receive prestigious prize for their significant scientific contribution to the European Planck mission.

After nearly a decade in space, the European Space Agency, ESA, is now completing the groundbreaking Planck mission. Planck was launched into space in 2009 to explore the origin of the universe in the period after the Big Bang.

Using data from Planck, researchers have, among other things, calculated that the universe is about 13.8 billion years old (13.787 billion years +/-0.020 billion years), and is thus slightly older than previously assumed.

The research team behind the mission recently received the prestigious Gruber Cosmology Prize, which is awarded by Yale University in the United States. Part of the credit goes to DTU Space, which has supplied equipment for Planck in the form of mirrors and has contributed to delivering groundbreaking research results based on the data collected by the spacecraft in space.

“The Planck mission has given us a lot more certainty in our knowledge of the early development of the universe. We’re proud to have contributed to this and of being awarded a prize,” says Hans Ulrik Nørgaard-Nielsen, who is astronomer at DTU Space and has been involved in the Planck mission from the outset.

“Highly accurate measurements have been made, and we have removed a lot of noise, which means that the cosmological quantities utilized in the description of the universe are now much more reliable. You must remember that we’re talking about finding knowledge by looking at tiny variations in light in space, and these can very easily be lost in ‘noise’ from other phenomena out there. So much of the work has been about cleaning our data, and it’s been a huge success.”

Before Planck entered space, the age of the universe had been calculated at 13.772 billion years, and the uncertainty regarding this figure was three times higher than in the new calculation.

More than 900 scientific publications
The Planck mission has provided a large amount of new knowledge, which has now been distributed on more than 900 scientific publications.

The mission has measured small variations in remnant light generated immediately after the Big Bang, a phenomenon called the cosmic microwave background or CMB. These small variations—where analyses of light are converted into small temperature differences which can be visualized by way of a map of the early universe—hold information about the age, expansion and contents of the universe.

When the Big Bang happened 13.8 billion years ago, the universe was so dense that light could not pass through. It was not until some 380,000 years later that the light emitted from the Big Bang could move through space. And it is this light which has now been mapped to a higher level of detail than the few previous missions have been able to.

In addition to determining the age of the universe, work has also been done to calculate how quickly the universe is expanding and to understand its origins.

DTU researcher demonstrates extreme expansion of the universe
The prevailing theory today is that the universe started with a phase called inflation—an extreme expansion of the universe for a fraction of a second. It then grew to the gigantic, visible universe we know today, and which is still expanding.

This theory can be confirmed through specific measurements of a phenomenon called B-modes. This is polarized light, which has a size and a direction. According to the theory, this phenomenon can only occur in connection with inflation.

"The Planck mission has given us a lot more certainty in our knowledge of the early development of the universe."
Hans Ulrik Nørgaard-Nielsen

So if B-modes can be detected in the Planck data and verified, it will be the first direct empirical evidence showing that the inflation phase did indeed occur.

And, in fact, Hans Ulrik Nørgaard-Nielsen has succeeded in detecting B-modes in the data sets from Planck on two occasions.

“At the moment, I’m the only one who has demonstrated this, and if it holds true, we have thus demonstrated inflation empirically,” says the DTU researcher, who has just had his second article on the discovery published in the scientific journal Astronomische Nachrichten.

However, there is no broad consensus among astronomers as to whether the B-modes and the demonstration of inflation are unequivocal.

“I’ve done the calculations based on two different data sets, and have reached the same result. Now it’s been published, and time will tell whether others will come to similar results and be able to confirm my findings along the way. That’s the nature of science,” says Hans Ulrik Nørgaard-Nielsen.

The last data set from the Planck mission was released by ESA earlier this summer. It is called ‘The Planck Legacy Data Release’.

This completes one of this millennium’s most significant space missions, on which DTU Space has made a big mark.

ESA's Planck-mission afsluttes 2018 med udgivelse af et sidste datasæt 'The Planck Lagacy Data release', som bruges til at generere et kort over det tidlige univers. (Illustration: ESA)

The illustration shows the distribution of heat in the universe in the form of small deviations.

The map has been composed on the basis of Planck’s measurements of variations in the cosmic microwave background in the form of remnant light emitted in connection with the Big Bang, which has been converted into small temperature differences. The red areas are hot spots in the universe, while the blue are cold spots.

Especially the blue, cold areas are interesting. The blue colour shows that the density was higher here than the average density in the early universe. This means that these areas may have gas clouds where the density is so high that they are able to contract using their own gravity. The formation of stars and galaxies can thus begin. The formation of our Milky Way, for example, started in this way.

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