European Space Agency’s Planck spacecraft has obtained the most accurate and detailed map ever made of the oldest light in the Universe. The map results suggest the Universe is expanding more slowly than scientists thought, and is 13,8 billion years old, 100 million years older than previous estimates. The data also show there is less dark energy and more matter in the Universe than previously known.
The newly estimated expansion rate of the Universe, known as Hubble’s constant, is 67,15 plus or minus 1,2 kilometres/second/megaparsec. A megaparsec is roughly 3 million light-years. This is less than prior estimates derived from space telescopes, such as Nasa’s Spitzer and Hubble, using a different technique. The new estimate of dark matter content in the universe is 26,8 per cent, up from 24 per cent, while dark energy falls to 68,3 per cent, down from 71,4 per cent. Normal matter now is 4,9 per cent, up from 4,6 per cent.
The map, based on the mission’s first 15,5 months of all-sky observations, reveals tiny temperature fluctuations in the cosmic microwave background, ancient light that has travelled for billions of years from the very early Universe to reach us. The patterns of light represent the seeds of galaxies and clusters of galaxies we see around us today.
“As that ancient light travels to us, matter acts like an obstacle course getting in its way and changing the patterns slightly,” said Charles Lawrence, the US project scientist for Planck at Nasa’s Jet Propulsion Laboratory. “The Planck map reveals not only the very young Universe, but also matter, including dark matter, everywhere in the Universe.”
Planck launched in 2009 and has been scanning the skies ever since, mapping the cosmic microwave background, the afterglow of the theorised big bang that created our Universe. This relic radiation provides scientists with a snapshot of the universe 370 000 years after the big bang.
The cosmic microwave background is remarkably uniform over the entire sky, but tiny variations reveal the imprints of sound waves triggered by quantum fluctuations in the Universe just moments after it was born. These imprints, appearing as splotches in the Planck map, are the seeds from which matter grew, forming stars and galaxies. Prior balloon-based and space missions learned a great deal by studying these patterns, including Nasa’s Wilkinson Microwave Anisotropy Probe (WMAP) and the Cosmic Background Explorer (COBE), which earned the 2006 Nobel Prize in Physics. Planck is the successor to these satellites, covering a wider range of light frequencies with improved sensitivity and resolution.
The age, contents and other fundamental traits of our Universe are described in the so-called “Standard Model” of cosmology, which has been developed over the years by astronomers. These new data have allowed researchers to test and improve the Standard Model with the greatest precision yet. At the same time, some curious features are observed that don’t quite fit with the simple picture. For example, the model assumes the sky is the same everywhere, but the light patterns are asymmetrical on two halves of the sky, and there is a spot extending over a patch of sky that is larger than expected.
“On one hand, we have a simple model that fits our observations extremely well, but on the other hand, we see some strange features, which force us to rethink some of our basic assumptions,” said Jan Tauber, the European Space Agency’s Planck project scientist based in the Netherlands. “This is the beginning of a new journey, and we expect our continued analysis of Planck data will help shed light on this conundrum.”
Complete results from Planck, which still is scanning the skies, will be released in 2014.