669 million galaxies catalogued in study seeking to explain universe's accelerating expansion
An international study that could reshape our understanding of gravity has released major results after 25 years of dark energy research.
An example of field in the southern constellation Lepus. It shows stars in the Milky Way (small colored dots) and a group of galaxies (the larger fuzzy objects) that is about 300 million light-years away. The image shows just a tiny part of one image captured by the Dark Energy Camera. DES analysis measures the faintest galaxies visible in this picture.
The Dark Energy Survey catalogued 669 million galaxies, using 140 million for precise measurements to help understand why the universe's expansion is accelerating rather than slowing down.
Einstein's theory of General Relativity predicted that gravity should slow cosmic expansion. But in 1998, astronomers discovered the opposite was happening. This means either 70% of the universe exists as "dark energy" with a repulsive gravitational force, or General Relativity must be replaced by a new theory of gravity on cosmic scales.
More than 400 scientists from seven countries used a 570-megapixel camera on a telescope in the Chilean Andes, observing the southern sky for 758 nights between 2013 and 2019.
Professor Bob Nichol, Pro-Vice-Chancellor and Executive Dean of the Faculty of Engineering and Physical Sciences at the University of Surrey, joined the collaboration at its inception, securing UK government funding for British scientists and holding several leadership positions.
The latest findings combine measurements of galaxy clustering, gravitational lensing and other cosmological probes, producing constraints more than twice as strong as previous analyses.
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Background:
The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.
Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from hundreds of millions galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.
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