A new map of the cosmic microwave background, the relic radiation from the Big Bang, completed in spring of 2013 by Europe's Planck satellite team refines our understanding of the Universe's composition and evolution, and unveils new features that could challenge the foundations of our current understanding of its evolution. Anomalies suggest that Universe may be different on scales larger than those we can directly observe. Most accurate values yet for the ingredients of the Universe, with normal matter contributing just 4.9% of the mass/energy density of the Universe and dark matter making up 26.8% - nearly a fifth more than the previous estimate.
The Plank data reveled two stunning new mysteries. The first is that we live in a lopsided universe. Einstein created the first physical model of the universe in 1917, know as the “cosmological principle,” which says that in the macro the universe looks the same in all locations, and in all directions because the physical laws governing its formation and expansion operate the same way everywhere. But what the Planck Spacecraft saw was very different: The cosmic microwave background is stronger in one half of the sky than in the other. There is also a large “cold” spot where the effective temperature of the microwaves is below average.
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. 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.
The spacecraft has compiled a trillion observations of a billion points on the sky, looking at each pixel in this image an average of 1,000 times. The Planck team had to rely on a series of computer simulations done on a Cray XE6 supercomputer known as the Hopper, located at Lawrence Berkeley National Laboratory. Those simulations made it possible to mimic and subtract the unwanted signals from foreground objects and from within the detectors. According to NASA, the current cosmic snapshot required 10 million processor-hours of time on the Hopper.
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 for our knowledge of the contents of the Universe.
"The CMB temperature fluctuations detected by Planck confirm once more that the relatively simple picture provided by the standard model is an amazingly good description of the Universe," explains George Efstathiou of the University of Cambridge, UK.
The properties of the hot and cold regions of the map provide information about the composition and evolution of the Universe. 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 slightly less than previously thought, at around 69%.
The Planck data also set a new value for the rate at which the Universe is expanding today, known as the Hubble constant. At 67.3 km/s/Mpc, this is significantly different from the value measured from relatively nearby galaxies. This somewhat slower expansion implies that the Universe is also a little older than previously thought, at 13.8 billion years.
The analysis also gives strong support for theories of "inflation", a very brief but crucial early phase during the first tiny fraction of a second of the Universe's existence. As well as explaining many properties of the Universe as a whole, this initial expansion caused the ripples in the CMB that we see today.
Although this primordial epoch can't be observed directly, the theory predicts a set of very subtle imprints on the CMB map. Previous experiments have not been able to confidently detect these subtle imprints, but the high resolution of Planck's map confirms that the tiny variations in the density of the early Universe match those predicted by inflation.
"The sizes of these tiny ripples hold the key to what happened in that first trillionth of a trillionth of a second. Planck has given us striking new evidence that indicates they were created during this incredibly fast expansion, just after the Big Bang", explained Joanna Dunkley of the University of Oxford.
But because the precision of Planck's map is so high, it also reveals some peculiar unexplained features that may well require new physics to be understood. Amongst the most surprising findings are that the fluctuations in the CMB over large scales do not match those predicted by the standard model. This anomaly adds to those observed by previous experiments, and confirmed by Planck, including an asymmetry in the average temperatures on opposite hemispheres of the sky, and a cold spot that extends over a patch of sky that is much larger than expected.
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.
The Hubble Deep Field image at the top of the page includes galaxies of various ages, sizes, shapes, and colors. The smallest, reddest galaxies, of which there are approximately 10,000, are some of the most distant galaxies to have been imaged by an optical telescope, probably existing shortly after the Big Bang.
The Daily Galaxy via ESA
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