Acquired by ESA’s Planck space telescope, the most detailed map ever created of the cosmic microwave background – the relic radiation from the Big Bang – was released today revealing 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 2700ºC. 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, we can
determine the composition and evolution of the Universe from its birth
to the present day.
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.
“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 François 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.
Copyright: ESA and the Planck Collaboration
New Cosmic Recipe
Beyond the anomalies, however, the Planck data conform spectacularly
well to the expectations of a rather simple model of the Universe,
allowing scientists to extract the most refined values yet for its
ingredients.
Normal matter that makes up stars and galaxies contributes just 4.9% of
the mass/energy density of the Universe. Dark matter, which has thus far
only been detected indirectly by its gravitational influence, makes up
26.8%, nearly a fifth more than the previous estimate.
Conversely, dark energy, a mysterious force thought to be responsible
for accelerating the expansion of the Universe, accounts for less than
previously thought.
Finally, the Planck data also set a new value for the rate at which the
Universe is expanding today, known as the Hubble constant. At
67.15 kilometres per second per megaparsec, this is significantly less
than the current standard value in astronomy. The data imply that the
age of the Universe is 13.82 billion years.
“With the most accurate and detailed maps of the microwave sky ever
made, Planck is painting a new picture of the Universe that is pushing
us to the limits of understanding current cosmological theories,” says
Jan Tauber, ESA’s Planck Project Scientist.
“We see an almost perfect fit to the standard model of cosmology, but
with intriguing features that force us to rethink some of our basic
assumptions.
“This is the beginning of a new journey and we expect that our continued
analysis of Planck data will help shed light on this conundrum.”
Note for Editors
For further information, please contact:
Markus Bauer
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int
George Efstathiou
University of Cambridge, UK
Tel: +44 1223 337530
Email: gpe@ast.cam.ac.uk
François Bouchet
Institut d’Astrophysique de Paris, France
Tel: +33 1 44 32 80 95
Email: bouchet@iap.fr
Paolo Natoli
University of Ferrara, Italy
Tel: +39 0532 97 42 44
Email: Paolo.Natoli@unife.it
Jan Tauber
ESA Planck Project Scientist
Tel: +31 71 565 5342
Email: Jan.Tauber@esa.int
Note for Editors
For further information, please contact:
Markus Bauer
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int
George Efstathiou
University of Cambridge, UK
Tel: +44 1223 337530
Email: gpe@ast.cam.ac.uk
François Bouchet
Institut d’Astrophysique de Paris, France
Tel: +33 1 44 32 80 95
Email: bouchet@iap.fr
Paolo Natoli
University of Ferrara, Italy
Tel: +39 0532 97 42 44
Email: Paolo.Natoli@unife.it
Jan Tauber
ESA Planck Project Scientist
Tel: +31 71 565 5342
Email: Jan.Tauber@esa.int
