Canadian astronomers are part of the international team that released results from the Planck Space Telescope Thursday. Results include an improved map of the most ancient light in the Universe, showing that it is slightly older than previously thought, expanding more slowly and that there is more matter than known before.
The map shown above is the most detailed map ever created of the cosmic microwave background – the relic radiation from the Big Bang. It shows the existence of features that challenge the foundations of our current understanding of the Universe. The image is based on the initial 15.5 months of data from Planck and is the mission’s first all-sky picture of the oldest light in our Universe, imprinted on the sky when it was just 380,000 years old.
At that time, the young Universe was filled with a hot dense soup of interacting protons, electrons and photons at about 2700 degC. When the protons and electrons joined to form hydrogen atoms, the light was set free. As the Universe has expanded, this light today has been stretched out to microwave wavelengths, equivalent to a temperature of just 2.7 degrees above absolute zero.
This ‘cosmic microwave background’ – CMB – shows tiny temperature fluctuations that correspond to regions of slightly different densities at very early times, representing the seeds of all future structure: the stars and galaxies of today.
According to the standard model of cosmology, the fluctuations arose immediately after the Big Bang and were stretched to cosmologically large scales during a brief period of accelerated expansion known as inflation.
Planck was designed to map these fluctuations across the whole sky with greater resolution and sensitivity than ever before. By analysing the nature and distribution of the seeds in Planck’s CMB image, astronomers can determine the composition and evolution of the Universe from its birth to the present day.
Planck was built by the European Space Agency and has been surveying the sky since launched in 2009. The telescope’s incredible accuracy allows it to pinpoint faint, minute patterns – differences in light and temperature that correspond to slightly different densities in the matter left over from the Big Bang.
The Planck spacecraft being prepared for launch in 2009. Credit: ESA
Planck’s data confirm and refine previous models of how astronomers believe the Universe originated and evolved, but with intriguing new details. The Planck team has calculated that the Universe is 13.82 billion years old – 100 million years older than earlier estimates. Planck has revealed that the Universe is expanding significantly slower than the current standard used by astronomers (known as Hubble’s Constant).
The space telescope has also allowed cosmologists to confirm the Universe’s composition more accurately than ever before: normal matter, the stuff of stars and galaxies like our own Milky Way, makes up just 4.9% of the Universe. Dark matter (an invisible substance that can only be inferred through the effects its gravity cause) accounts for 26.8%. Dark energy, a mysterious force that behaves the opposite way to gravity, pushing and expanding our Universe, makes up 68.3% of the Universe – slightly less than previously thought.
The Canadian Space Agency funds two Canadian research teams that are part of the Planck science collaboration. The team helped develop both of Planck’s complementary science instruments, the High Frequency Instrument (HFI) and the Low Frequency Instrument (LFI). Professors J. Richard Bond of the University of Toronto (Director of Cosmology and Gravity at the Canadian Institute for Advanced Research) and Douglas Scott of the University of British Columbia lead the Canadian Planck team, which includes members from the University of Alberta, Universit Laval and McGill University.
“We now have a precise recipe for our Universe: how much dark and normal matter it is made of; how fast it is expanding; how lumpy it is and how that lumpiness varies with scale; and how the remnant radiation from the Big Bang is scattered,” said University of British Columbia Professor Douglas Scott. “It is astonishing that the entire Universe seems to be describable by a model using just these 6 quantities. Now, Planck has told us the values of those numbers with even higher accuracy.”
Planck’s precision has also given astrophysicists a number of new puzzles to solve.
“For more than three decades, I have been trying to unveil the structure imprinted on the Universe from an epoch of accelerated expansion in its earliest moments,” said Professor J. Richard Bond of the University of Toronto. “Planck has now shown that the evidence for this early inflation is much stronger than before. The patterns we see are quite simple, resulting in many formerly viable theories falling victim to our Planckian knife. Our maps reveal unexplained, large-scale features that excite the imaginations of physicists who have been eagerly awaiting what Planck has to say about the early Universe.”
“We do not simply sweep away the dust signal into the trash bin, but rather treasure it for what it tells us about the workings of the Galaxy. It enables us to discover the evolution of structure in the interstellar medium leading from a diffuse state to star formation in dense molecular clouds,” said Professor Peter Martin of the University of Toronto.
Overall, the information extracted from Planck’s new map provides an excellent confirmation of the standard model of cosmology at an unprecedented accuracy, setting a new benchmark in our manifest of the contents of the Universe.
But because precision of Planck’s map is so high, it also made it possible to reveal some peculiar unexplained features that may well require new physics to be understood.
At a Press conference in Paris Thursday morning, European astronomers commented on the findings.
“The extraordinary quality of Planck’s portrait of the infant Universe allows us to peel back its layers to the very foundations, revealing that our blueprint of the cosmos is far from complete. Such discoveries were made possible by the unique technologies developed for that purpose by European industry,” says Jean-Jacques Dordain, ESA’s Director General.
“Since the release of Planck’s first all-sky image in 2010, we have been carefully extracting and analysing all of the foreground emissions that lie between us and the Universe’s first light, revealing the cosmic microwave background in the greatest detail yet,” adds George Efstathiou of the University of Cambridge, UK.
One of the most surprising findings is that the fluctuations in the CMB temperatures at large angular scales do not match those predicted by the standard model – their signals are not as strong as expected from the smaller scale structure revealed by Planck.
Another is an asymmetry in the average temperatures on opposite hemispheres of the sky. This runs counter to the prediction made by the standard model that the Universe should be broadly similar in any direction we look.
Furthermore, a cold spot extends over a patch of sky that is much larger than expected.
The asymmetry and the cold spot had already been hinted at with Planck’s predecessor, NASA’s WMAP mission, but were largely ignored because of lingering doubts about their cosmic origin.
“The fact that Planck has made such a significant detection of these anomalies erases any doubts about their reality; it can no longer be said that they are artefacts of the measurements. They are real and we have to look for a credible explanation,” says Paolo Natoli of the University of Ferrara, Italy.
“Imagine investigating the foundations of a house and finding that parts of them are weak. You might not know whether the weaknesses will eventually topple the house, but you’d probably start looking for ways to reinforce it pretty quickly all the same,” adds Francois Bouchet of the Institut d’Astrophysique de Paris.
One way to explain the anomalies is to propose that the Universe is in fact not the same in all directions on a larger scale than we can observe. In this scenario, the light rays from the CMB may have taken a more complicated route through the Universe than previously understood, resulting in some of the unusual patterns observed today.
“Our ultimate goal would be to construct a new model that predicts the anomalies and links them together. But these are early days; so far, we don’t know whether this is possible and what type of new physics might be needed. And that’s exciting,” says Professor Efstathiou.