Cosmic map reveals a not-so-lumpy Universe
Cosmologists have produced the biggest map yet of the Universe’s structure and they find it less lumpy than previous surveys have suggested.
The new results, part of the ongoing Dark Energy Survey (DES), charted the distribution of matter in part by measuring the way that mass bends light, an effect known as gravitational lensing. The Universe was extremely smooth, with matter evenly distributed in its infancy nearly 14 billion years ago, but mass has been clumping together ever since into galaxies, gas clouds and other structures. Data released by the DES team on 3 August suggest that the clumping has happened more slowly than indicated by earlier estimates, which were based on baby pictures of the Universe made by measuring the cosmic microwave background, the afterglow of the Big Bang.
The difference in the results produced by the two techniques is still within the margins of error in both sets of measurements, say the survey leaders. A smaller gravitational-lensing survey, the Kilo Degree Survey (KiDS) also found a similar discrepancy last year.
New Clues to Universe's Structure Revealed
What is our universe made of, and has its composition changed over time? Scientists have new insights about these fundamental questions, thanks to an international collaboration of more than 400 scientists called the Dark Energy Survey (DES). Three scientists from NASA's Jet Propulsion Laboratory in Pasadena, California, are part of this group that is helping to further our understanding of the structure of the universe.
The results are especially important to the scientific community because they mark the first time that observations from the more recent universe -- the "adult" universe -- by a technique called gravitational lensing and galaxy clustering, have yielded results as precise as those from the cosmic microwave background radiation -- light from the "infant" universe.
"This is the crossover point where gravitational lensing and galaxy clustering measurements and surveys will be the primary driver of what we know about dark energy in the universe," said Eric Huff, a JPL researcher who invented a new method of extracting the weak lensing signal, enhancing the precision of the DES galaxy shape catalogs.
Dark Energy Survey reveals most accurate measurement of dark matter structure in the universe
Imagine planting a single seed and, with great precision, being able to predict the exact height of the tree that grows from it. Now imagine traveling to the future and snapping photographic proof that you were right.
If you think of the seed as the early universe, and the tree as the universe the way it looks now, you have an idea of what the Dark Energy Survey (DES) collaboration has just done. In a presentation today at the American Physical Society Division of Particles and Fields meeting at the U.S. Department of Energy’s (DOE) Fermi National Accelerator Laboratory, DES scientists will unveil the most accurate measurement ever made of the present large-scale structure of the universe.
These measurements of the amount and “clumpiness” (or distribution) of dark matter in the present-day cosmos were made with a precision that, for the first time, rivals that of inferences from the early universe by the European Space Agency’s orbiting Planck observatory. The new DES result (the tree, in the above metaphor) is close to “forecasts” made from the Planck measurements of the distant past (the seed), allowing scientists to understand more about the ways the universe has evolved over 14 billion years.
“This result is beyond exciting,” said Scott Dodelson of Fermilab, one of the lead scientists on this result. “For the first time, we’re able to see the current structure of the universe with the same clarity that we can see its infancy, and we can follow the threads from one to the other, confirming many predictions along the way.”