Planck results: Universe older, slower and still challenging
On 21 March 2013, ESA’s Planck satellite revealed the most detailed map ever created of the cosmic microwave background [CMB], the relic radiation from the Big Bang. The results from Planck’s new map provided an excellent confirmation of the standard model of cosmology with unprecedented accuracy. However, the existence of unexplained features may challenge the foundations of the current understanding of the Universe.
According to the Big Bang theory, the Universe rapidly expanded from extremely hot and dense plasma of photons, electrons, and protons. Only after 380 000 years, the Universe cooled sufficiently – at about 3000K – to permit the combination of protons and electrons to form neutral hydrogen atoms, setting the photons free so the Universe was finally transparent to radiation. As the Universe has expanded, this light has been stretched out to microwave wavelengths, which can be observed by Planck.
Planck’s map shows tiny temperature fluctuations that correspond to regions of slightly different densities, i.e. represent the seeds forming the current stars and galaxies. Planck was designed to map these fluctuations across the whole sky with greater resolution and sensitivity than ever before.
The Planck team found that the Universe is expanding at a slightly slower rate than was thought, making it around 13.82 billion years old, slightly older than previous estimates. Planck has also modified our understanding of the fundamental recipe of the Universe, with ordinary and dark matter making up a rather larger percentage than before and dark energy, a mysterious force thought to be responsible for accelerating the expansion of the Universe, accounts for less than previously estimated.
The precision of Planck’s map is so high that it also made it possible to reveal some unexplained features that may well require new physics to be understood. 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. Another is that the CMB map looks different in opposite hemispheres of the sky, implying that the universe is not the same in all directions.
Planck’s CMB map is based on the initial 15.5 months of operations. The analysis of the Planck data is due to continue, with the full mission results expected in 2014.
More information can be found in ESA website.
