Free Astronomy Magazine May-June 2021

28 MAY-JUNE 2021 ASTRO PUBLISHING The detailed precision cos- mology constraints based on the full six-year DES dataset will come out over the next two years. DES was conceived to map hundreds of millions of galaxies and to chart the size of the expanding Uni- verse as it accelerates under the influence of dark en- ergy. DES has produced the largest and most accurate dark matter map from gal- axy weak lensing to date. Covering 5,000 square de- grees of the southern sky, the survey data enable many other investigations in addition to those targeting dark energy, covering a vast range of cosmic distances — from discovering new nearby Solar System objects to investigating the nature of the first star-forming gal- axies in the early Universe. “This is a momentous mile- stone. For six years, the Dark Energy Survey collaboration took pictures of distant ce- lestial objects in the night sky. Now, after carefully checking the quality and calibration of the images captured by the Dark En- ergy Camera, we are releas- ing this second batch of data to the public,” said DES Director Rich Kron of Fermi- lab and the University of Chicago. “We invite professional and amateur scientists alike to dig into what we consider a rich mine of gems waiting to be discovered.” The primary tool used to collect these images, the Dark Energy Cam- era (DECam), fabricated by DOE, is mounted on the National Science Foundation-funded Víctor M. Blanco 4-meter Telescope, part of the Cerro Tololo Inter-American Observatory T he irregular dwarf galaxy IC 1613 contains some 100 million stars and is a member of our Local Group of galaxies, which also includes our Milky Way, the Andromeda spiral galaxy, and the Magellanic Clouds. Also this image is an excerpt from the Dark Energy Survey. [DES/DOE/Fermilab/NCSA & CTIO/NOIRLab/NSF/AURA - Ack: Image processing: DES, Jen Miller (Gemini Observatory/NSF’s NOIRLab), Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin] tion of the RR Lyrae stars hints at the presence of an enormous “halo” of invisible dark matter, which may provide clues to how our galaxy was assembled over the last 12 billion years. In another result, DES scien- tists used the extensive DR2 galaxy catalog, along with data from the LIGO gravitational wave experi- ment, to estimate the location of a black hole merger and, independent of other techniques, infer the value of the Hubble constant, a key cos- mological parameter. Combining their data with other surveys, DES scientists have also been able to generate a detailed map of the Milky Way’s dwarf satel- lites, giving researchers insight into how our own galaxy was assembled and how it compares with cosmolo- gists’ predictions.