Scientists have achieved a groundbreaking milestone in understanding the universe's mysteries, revealing a clearer picture of the dark universe than ever before. This achievement is attributed to the meticulous analysis of six years' worth of data collected by the Dark Energy Camera (DECam) on the U.S. National Science Foundation Víctor M. Blanco 4-meter telescope.
The data, analyzed by the Dark Energy Survey (DES) Collaboration between 2013 and 2019, encompasses 758 nights of observations of one-eighth of the sky. It includes information from 669 million galaxies located billions of light-years from Earth. This extensive dataset has provided scientists with unprecedented insights into the expansion of the universe and the enigmatic force driving its acceleration, known as dark energy.
"These results from DES shine new light on our understanding of the universe and its expansion," said Regina Rameika, Associate Director for the Office of High Energy Physics in the Department of Energy’s Office of Science. "They demonstrate how long-term investment in research and combining multiple types of analysis can provide insight into some of the universe’s biggest mysteries."
The discovery of dark energy in 1998, when astronomers observed distant supernovas and found that their recession velocity increased with distance, confirmed the expanding universe theory proposed by Edwin Hubble. However, it also revealed a shocking acceleration in this expansion, prompting scientists to label the driving force as dark energy. Since then, dark energy has been found to account for approximately 68% of the cosmos' total energy and matter budget.
The new analysis, in addition to Type-Ia supernovas, incorporated three other cosmic phenomena: weak gravitational lensing, galaxy clustering, and baryon acoustic oscillations. These phenomena offer diverse perspectives on the universe's structure and expansion. Yuanyuan Zhang, a member of the DES Collaboration, expressed the awe of witnessing these results, stating, "It is an incredible feeling to see these results based on all the data, and with all four probes that DES had planned."
The DES team utilized DECam data and advanced techniques to reconstruct the distribution of matter over the past 6 billion years of cosmic history. They then compared these findings with two prevailing models of the universe: the standard Lambda Cold Dark Matter (LCDM) model and the extended wCDM model. While the results aligned well with both models, a critical parameter revealed a discrepancy.
The study found that modern galaxies do not cluster as predicted by either the LCDM or wCDM models, with the observed differences becoming more pronounced. This highlights the ongoing challenge of understanding dark energy and its role in the universe's evolution.
Looking ahead, the DES team plans to integrate DECam data with observations from the Vera C. Rubin Observatory's Legacy Survey of Space and Time, which will provide an even clearer picture of the universe's history and the nature of dark energy. This collaboration will enable new tests of gravity and shed further light on the enigmatic force that drives the universe's expansion.
