From 2013 to 2019, dark energy investigation (DES) conducted a deep and wide-ranging survey of the sky in a collaborative effort to map hundreds of millions of galaxies, thousands of supernovae, and measure the rate of expansion of the universe. For more than a century, scientists have been trying to suppress this cosmological phenomenon. Hubble-Lemaître constant – Named after astronomers Edwin Hubble and Georges Lemaître, who independently confirmed that the universe was expanding in the early 20th century.
above January 22ndDES announced the results of a six-year campaign, providing the first comprehensive data set that includes all four methods of measuring the expansion of the universe: baryon acoustic oscillations (BAOs), type Ia supernovae, galaxy clusters, and weak gravitational lensing. This analysis imposes constraints that are more than twice as strict as previous DES analyses, thereby narrowing down the set of possible models for how the universe behaves at the largest scales.
influence of darkness
In doing so, scientists aim to measure impacts such as: dark energy (DE) is the mysterious force responsible for this expansion, which has been accelerating for the past 4 billion years. The first signs of DE appeared just a few years earlier with Hubble and Lemaître, who both proved and discredited an important theory proposed by Albert Einstein. According to the field equations of Einstein’s theory of general relativity, some force was needed to “suppress gravity” and prevent the universe from collapsing and imploding.
*Victor M. Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory (CTIO). Credit: NSF NOIRLab*
In Einstein’s view, this cosmological constant (as he called it) had enough power to keep the universe in static and eternal balance. He represented this unknown force in his equations using the Greek letter lambda (Λ). However, as his contemporaries pointed out, depending on the value of the constant, the universe could also be in a state of expansion. Einstein rejected this idea in favor of an eternal universe that is not subject to expansion or contraction. In 1931, Hubble invited Einstein to Mount Wilson Observatory in California to witness what he had observed years earlier.
While there, Hubble showed Einstein how redshift measurements showed the galaxy was moving away from our galaxy. In fact, the farther away a galaxy was, the faster it was moving away from us. Witnessing this, Einstein declared the cosmological constant the “biggest mistake” of his career. But in 1998, two independent teams of cosmologists discovered that the expansion of the universe was being accelerated by distant supernovae. This contradicted astronomers’ previous predictions that gravity would slow expansion over time and the universe would begin to recede.
This led them to propose that another phenomenon was responsible for the expansion of the universe, which became known as “dark energy.” In honor of Einstein’s original suggestion that there is a force in the universe that defies gravity, DE is also represented by the letters lambda. Today, astrophysicists hypothesize that this force accounts for about 70% of the mass-energy density of the universe, but little is known about it. Over the next few years, scientists began devising experiments to study DE, which came to fruition on August 31, 2013, when DES began exploring the universe.
Please enter DES
DES is an international collaboration led by DOE’s Fermi National Accelerator Laboratory and involving more than 400 scientists from 35 institutions in seven countries. This organization uses 570 million pixels to monitor space dark energy camera (DECam) mounted on the 4-meter Victor M. Blanco Telescope at NSF Cerro Tololo Interamerican Observatory (CTIO) Chile. Over six years and 758 nights, the DES collaboration used these four methods to obtain information about one-eighth of the sky, including 669 million galaxies located billions of light-years from Earth.
“Based on all the data, it feels incredible to see results like this for all four of DES’ planned spacecraft,” said Yuanyuan Zhang, assistant astronomer at the NSF NOIRLab and a member of DES. “This is something DES could only have dreamed of when we started collecting data, and now that dream has come true.”
“These results from the Dark Energy Survey shed new light on our understanding of the Universe and its expansion,” added Regina Lameika, associate director of the High Energy Physics Office at the Department of Energy’s Office of Science (DOE/SC). “It shows how a combination of long-term investment in research and multiple types of analysis can provide insight into some of the universe’s greatest mysteries.”
In this latest analysis, DES tested two models of dark energy against six years of DES observations. These include the currently accepted standard model of cosmology, lambda cold dark matter (ΛCDM), and wCDM models. The ΛCDM model considers the DE density to be constant, while the latter assumes the DE density to be constant. evolving phenomenon. However, their results were inconclusive as their data fit both cosmological models equally well. Additionally, their results confounded the galaxy cluster parameter, one of the four parameters used to measure the expansion of the universe.
Based on measurements from the early Universe, both DE models predict how matter will cluster in later cosmological epochs. Previous analyzes of galaxy clustering have not matched the predictions of these models, but recent data have only widened that gap (but not enough to rule out one of them). As a next step, the DES collaboration will investigate its results in combination with the latest constraints from other DE experiments. modified newton mechanics (MOND), an alternative theory of gravity that does not require DE.
This analysis also paves the way for complementary data collected by the Vera C. Rubin Observatory, which observes 20 billion galaxies across the Southern Hemisphere sky as part of the Legacy Space-Time Survey (LSST). This data, combined with experiments such as DES, will enable even tighter constraints on cosmological parameters and further improve our understanding of the expansion history of the universe.
Read more: NSF NOIRLab, Physical Review D.