Planck shows an homogeneous Universe
On March 21, the Planck scientific team released the first set of cosmology results based on data obtained during the first 15.5 months of the Space Telescope's operation. This has been done be means of almost thirty scientific articles in which the Cosmology group of CEFCA has been involved.
Planck is a satellite of the European Space Agency (ESA) designed to analyse with unprecedented sensitivity and resolution remnants of the radiation that filled the Universe immediately after the Big Bang, and that we can observe today as the Cosmic Microwave Background (CMB, for its acronym in English).
After the Cosmic Background Explorer (COBE) missions of the nineties and the Wilkinson Microwave Anisotropy Probe (WMAP) of the two thousand decade, Planck represents the third generation of space telescopes dedicated to the study of the universe in its early stages. Its main function is to test theories about how the universe was and to know the origin of its structure. In this way, it is possible to determine its composition and its evolution from its birth to the present.
One of the most significant discoveries led by researchers from CEFCA reveals that the present universe is uniform on very large scales, or in other words, that there are no regions of the universe which are much more denser than others. The Planck study limits the velocities of the galaxy clusters, showing that these speeds are very small in the Universe at large scale, and therefore galaxy clusters do not suffer the accelerations that would generate the gravitational attraction due to the presence of 'lumps' in the Universe.
CEFCA cosmologist, Dr. Carlos Hernandez-Monteagudo, explains: "Until now there was an open debate in the cosmology field about whether or not the universe is homogeneous. There are theories and recent studies that state that a huge volume of the universe, in which we are included, falls with accelerated speeds of about 1000 km/s to a specific point. This requires a model of inhomogeneous universe on large scales and poses a serious problem for the standard model. Planck data discard these theories showing that the velocities for that volume are very small and therefore there are no significant overdensities that justify the behaviour."
In addition to these results, CEFCA in coordination with researchers from the Instituto de Física de Cantabria (IFCA) and the University of Heidelberg have tried to see the effect of the accelerated expansion of the Universe on the CMB in order to conduct an independent test. According to Dr. Hernandez-Monteagudo, "to see this effect is difficult, but Planck has allowed us to see different evidencies of its presence that, in spite of not being statistically significant individually, they show a high degree of consistency among them."
The discovery of the accelerated expansion of the Universe through observations of distant supernovae is one of the major milestones in the history of modern cosmology. In fact, as a result of this investigation Dr. Saul Perlmutter, and then Dr. Brian Schmidt and Dr. G. Adam Riess were awarded the Nobel Prize in Physics on 2011.