The most detailed dark-matter map of our universe is weirdly clean
The DES is an effort to picture as many galaxies as doable as a proxy for mapping out darkish matter, which is feasible as a result of darkish matter’s gravity performs a robust position in governing how these galaxies are distributed. From August 2013 to January 2019, dozens upon dozens of scientists got here collectively to make use of the four-meter Victor M. Blanco Telescope in Chile to survey the sky in close to infrared.
There are two keys to creating the map. The first is solely observing the situation and distribution of galaxies all through the universe. That association clues scientists in to the place the most important concentrations of darkish matter are situated.
The second is observing gravitational lensing, a phenomenon by which the sunshine emitted by galaxies is gravitationally stretched by darkish matter because it strikes by means of area. The impact is much like wanting by means of a magnifying glass. Scientists use gravitational lensing to deduce how a lot precise area close by darkish matter is taking over. The extra distorted the sunshine, the clumpier the darkish matter.
The newest outcomes take into consideration the primary three years of DES knowledge, tallying greater than 226 million galaxies noticed over 345 nights. “We are now able to map out dark matter over a quarter of the Southern Hemisphere,” says Niall Jeffrey, a researcher from University College London and École Normale Supérieure in Paris, one of many DES undertaking leads.
DARK ENERGY SURVEY
In common, the info traces up with the so-called Standard Model of Cosmology, which posits that the universe was created within the Big Bang and that its whole mass-energy content material is 95% darkish matter and darkish power. And the brand new map supplied scientists with a extra detailed take a look at some huge dark-matter buildings of the universe that in any other case stay invisible to us. The brightest spots on the map characterize the very best concentrations of darkish matter, they usually kind clusters and halos round voids of very low densities.
But some outcomes have been shocking. “We found hints that the universe is smoother than expected,” says Jeffrey. “These hints are also seen in other gravitational-lensing experiments.”
This is just not what’s predicted by common relativity, which means that darkish matter ought to be extra clumpy and fewer uniformly distributed. The authors write in one of many 30 papers being launched that “though the evidence is by no means definitive, we are perhaps beginning to see hints of new physics.” For cosmologists, “this would correspond to possibly changing the laws of gravity as described by Einstein,” says Jeffrey.
Although the implications are large, warning is paramount, as a result of we nonetheless truly know so little about darkish matter (one thing we’ve but to immediately observe). For instance, Jeffrey notes that “if nearby galaxies form in an alignment in a strange way due to complex astrophysics, then our lensing results would be misled.”
In different phrases, there would possibly very properly be some unique explanations for the outcomes—maybe accounting for them in methods which are reconcilable with common relativity. That could be an enormous aid to any astrophysicist whose total life’s work relies on Einstein being, properly, appropriate. And let’s not overlook: common relativity has stood up remarkably properly to each different take a look at that has been thrown at it through the years.
The outcomes are already making waves, even with a number of extra DES knowledge releases pending. “Already, astronomers are using these maps to study the structures of the cosmic web and understand the connection between galaxies and dark matter better,” says Jeffrey. We might not have to attend too lengthy to seek out out whether or not the outcomes actually are a blip or our understanding of the universe wants some large rewriting.
Source www.technologyreview.com
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