Dark Energy Survey (DES): Five-year mission to map southern sky in detail

This image of the NGC 1398 galaxy was taken with the Dark Energy Camera (DECam). 

This galaxy lives in the Fornax cluster, roughly 65 million light years from Earth. 

It is 135,000 light years in diameter, just slightly larger than our own Milky Way galaxy, and contains more than a hundred million stars. 

Credit: Dark Energy Survey.

Tonight, as the sun sinks below the horizon, the world's most powerful digital camera will once again turn its gleaming eye skyward.

Tonight, and for hundreds of nights over the next five years, a team of physicists and astronomers from around the globe will use this remarkable machine to try to answer some of the most fundamental questions about our universe.

Dark Energy Survey - DECam: Fermilab  

On Aug. 31, the Dark Energy Survey (DES) officially began. Scientists on the survey team will systematically map one-eighth of the sky (5000 square degrees) in unprecedented detail.

The start of the survey is the culmination of 10 years of planning, building and testing by scientists from 25 institutions in six countries.

The survey's goal is to find out why the expansion of the universe is speeding up, instead of slowing down due to gravity, and to probe the mystery of dark energy, the force believed to be causing that acceleration.

James Siegrist

"The Dark Energy Survey will explore some of the most important questions about our existence," said James Siegrist, associate director for High Energy Physics at the U.S. Department of Energy's Office of Science.

"In five years' time, we will be far closer to the answers, and far richer in our knowledge of the universe."

"With the start of the survey, the work of more than 200 collaborators is coming to fruition," said DES Director Josh Frieman of the U.S. Department of Energy's Fermi National Accelerator Laboratory.

"It's an exciting time in cosmology, when we can use observations of the distant universe to tell us about the fundamental nature of matter, energy, space and time."

Composite Dark Energy Camera image of one of the sky regions that the collaboration will use to study supernovae, exploding stars that will help uncover the nature of dark energy. 

The outlines of each of the 62 Charged Coupled Devices can be seen. 

This picture spans 2 degrees across on the sky and contains 520 megapixels.

The survey will use four methods to probe dark energy:

• Counting galaxy clusters. While gravity pulls mass together to form galaxies, dark energy pulls it apart. The Dark Energy Camera will see light from 100,000 galaxy clusters billions of light-years away. Counting the number of galaxy clusters at different points in time sheds light on this cosmic competition between gravity and dark energy.
• Measuring supernovae. A supernova is a star that explodes and becomes as bright as an entire galaxy of billions of stars. By measuring how bright they appear on Earth, we can tell how far away they are. Scientists can use this information to determine how fast the universe has been expanding since the star's explosion. The survey will discover 4000 of these supernovae, which exploded billions of years ago in galaxies billions of light-years away. 
• Studying the bending of light. When light from distant galaxies encounters dark matter in space, it bends around the matter, causing those galaxies to appear distorted in telescope images. The survey will measure the shapes of 200 million galaxies, revealing the cosmic tug of war between gravity and dark energy in shaping the lumps of dark matter throughout space.
• Using sound waves to create a large-scale map of expansion over time. When the universe was less than 400,000 years old, the interplay between matter and light set off a series of sound waves traveling at nearly two-thirds the speed of light. Those waves left an imprint on how galaxies are distributed throughout the universe. The survey will measure the positions in space of 300 million galaxies to find this imprint and use it to infer the history of cosmic expansion.