Astronomers have used the largest sample of galaxies observed ever, covering nearly one-eighth of the sky, to produce the most precise measurements of the composition and growth of the universe.
The first three years of data from the Dark Energy Survey (DES) have been published. Astronomers used observations of over 226 million galaxies to create the largest ever map of the distribution of galaxies, extending more than 7 billion light-years into the cosmos. The results will make astronomers breathe a sigh of relief. The Standard Model of Cosmology, the main theory underpinning our understanding of the universe, continues to be by far the best model of the cosmos.
The standard model requires the universe to be made of three main components: Regular matter, which is what we are made of; dark matter, an invisible substance that permeates everywhere and outweighs regular matter five to one; and dark energy, the most abundant component, responsible for the accelerated expansion of the universe.
“These analyses are truly state-of-the-art, requiring artificial intelligence and high-performance computing super-charged by the smartest young scientists around,” said Scott Dodelson, a physicist at Carnegie Mellon University who co-leads the DES Science Committee with Elisabeth Krause of the University of Arizona, said in a statement. “What an honor to be part of this team.”
The results of this enormous data release are collected in 30 scientific papers and have allowed astronomers and physicists to tighten the constraints of what we know about the mysterious dark matter and dark energy as well as the theory that requires them. The teams also compared the current results to the map of the cosmic microwave background (CMB), the first light that shone freely in the universe, which is also used to test the standard model.
The data are both consistent with each other and with the model, thankfully. In cosmology, there is an ongoing tension between the expectation from the CMB and the expectation from galaxies in the closer universe. The DES has not found anything that is about to shift our understanding but a hint remains that the universe appears to be a little bit smoother than predicted from the analysis of the CMB.
“It would be very exciting to find contradictions between galaxy surveys like DES and analyses of the CMB, as they would provide hints of new physics. This observed difference in the clustering of matter could be one such contradiction, but we will need more data to confirm it,” Dr Pablo Lemos (both UCL Physics & Astronomy and Sussex University), co-author of the new analysis paper, said in a statement.
The Standard Model remains firmly safe but will continue to be tested as any theory should be. The data release from DES is about half of the total observations conducted so more stringent tests will come. The DES collaboration consists of over 400 scientists from 25 institutions in seven countries.
“The collaboration is remarkably young. It’s tilted strongly in the direction of postdocs and graduate students who are doing a huge amount of this work,” DES Director and spokesperson Rich Kron, who is a Fermilab and University of Chicago scientist, said in a statement. “That’s really gratifying. A new generation of cosmologists are being trained using the Dark Energy Survey.”