The Dark Energy Survey takes the most accurate measurements yet of the composition and growth of the universe through astronomy


Within six years, astronomers from the Dark Energy Survey (DES) have measured 5,000 square degrees – almost an eighth of the entire sky – and cataloged hundreds of millions of objects in 758 observation nights. Their results, published in 29 new publications, draw on data from the first three years of the survey – 226 million galaxies observed in 345 nights – to produce the largest and most accurate maps of the distribution of galaxies in the universe in relative terms to date to create young eras.

This deep field image from the Dark Energy Survey is full of galaxies. In fact, almost every single object in this picture is a galaxy. A few exceptions are a few dozen asteroids as well as a handful of foreground stars in our own Milky Way Galaxy. Photo credit: Dark Energy Survey / DOE / FNAL / DECam / CTIO / NOIRLab / NSF / AURA / TA Rector, University of Alaska Anchorage & NOIRLab / M. Zamani, NOIRLab / D. de Martin, NOIRLab.

DES images the night sky with the 570 megapixel dark energy camera of the 4 m telescope Víctor M. Blanco from NSF at the Inter-American Observatory Cerro Tololo in Chile, a program of NSF’s NOIRLab.

The Dark Energy Camera, one of the most powerful digital cameras in the world, was specially developed for this survey.

“NOIRLab is a proud host and member of the DES collaboration,” said Dr. Steve Heathcote, associate director of the Cerro Tololo Inter-American Observatory.

“Both during and after the survey, the Dark Energy Camera was a popular choice for community and Chilean astronomers.”

To test the current model of the cosmologists’ universe, the DES astronomers compared their results with measurements from the ESA’s Planck observatory.

Planck used light signals known as the cosmic microwave background to return to the early universe just 400,000 years after the Big Bang.

The Planck data gives an accurate overview of the universe 13 billion years ago, and the standard cosmological model predicts how dark matter should evolve up to the present.

If DES observations do not agree with this prediction, there may be an undiscovered aspect in the universe.

While there has been persistent evidence from DES and several previous galaxy surveys that the current universe is a few percent less lumpy than predicted – a fascinating finding worth investigating further – the recently published results are in line with the prediction.

“In the area of ​​limiting our knowledge of the distribution and structure of matter on a large scale, powered by dark matter and dark energy, DES has reached limits that rival and complement those of the cosmic microwave background,” said Dr. Brian Yanny. an astronomer at DOE Fermilab.

“It’s exciting to have accurate measurements of what’s out there and a better understanding of how the universe has changed from its infancy to the present day.”

In order to quantify the distribution of dark matter and the effect of dark energy, the researchers relied mainly on two phenomena.

First, large-scale galaxies are not randomly distributed in space, but rather form a weblike structure that is due to the gravity of dark matter.

DES has measured how this cosmic web has evolved over the course of the history of the universe. The galaxy clusters that make up the cosmic web revealed regions with a higher density of dark matter.

Second, DES recognized the signature of dark matter through weak gravitational lenses.

As light from a distant galaxy moves through space, gravity in both the ordinary and dark matter in the foreground can bend its way like a lens, resulting in a distorted image of the galaxy from Earth.

By studying how the apparent shapes of distant galaxies align with each other and with the positions of neighboring galaxies along the line of sight, DES scientists were able to infer the clumping of dark matter in the universe.

“These analyzes are really state-of-the-art and require artificial intelligence and high performance computing powered by the brightest young scientists,” said Dr. Scott Dodelson, a physicist at Carnegie Mellon University.


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