New doubts about dark energy
Belle Dumas, physicsweb
(Translation: Dikla Oren)
Most astronomers believe that "dark energy" dominates the universe, because this is the only way to explain the expansion of the universe and its acceleration at the same time. Now, however, physicists from the Netherlands and France suggest that this energy may not exist. They claim that the lack of dark energy can be explained with the help of X-ray observations of the universe, which reveal puzzling differences between galaxy clusters in the future and today.
In February, NASA unveiled the first complete and detailed map of the cosmic background radiation - the echo of the Big Bang. The information, collected by the WMAP (Wilkinson Microwave Anisotropy Probe) satellite, supports the current popular "harmonic model" of the universe. This model predicts that the universe consists of 5% normal matter, 25% dark matter that cannot be seen, and 70% dark energy. Although the nature of dark energy is still unknown, galaxies in such a universe, where the density of matter is so low, should have stopped growing in the early days of the universe. Because all of them should look today as they looked in the past.
David Lamb and his colleagues at the Netherlands Space Research and Technology Center (ESTEC) have now measured eight distant galaxies with the XMM-Newton. These galaxies - the most distant of which is about ten billion light years away - provide us with a snapshot of the universe, as it was about seven billion years ago. Lamb and his colleagues surprisingly found that galaxies in the distant universe emit more X-rays than those in the closer universe.
Moreover, another group of physicists, headed by Alain Blanchard from the Midi-Pyrenees Observatory, analyzed the information and showed that the universe is a dense environment that contains more matter than is commonly thought. "To explain these results requires a lot of matter in the universe - and that doesn't leave much room for dark energy," Blanchard said. The information, if confirmed, could have important implications for the harmonic model of the universe and other fundamental assumptions about the nature of the universe.
