The Lambda-CDM (λCDM) model has been the basis of modern cosmology for some time, and it successfully explains the large-scale structure of the universe. It proposes that 95% of cosmos consists of dark matter (25%) and dark energy (70%). Dark energy, represented by the cosmic constant (λ), is thought to promote accelerated expansion of the universe, and maintains a constant energy density over time. However, new results from the dark energy research suggest a departure from this assumption, suggesting that dark energy may evolve over time.
This artist's impression shows the evolution of the universe, beginning with the Big Bang on the left. After that, you will see the microwave background of the universe. The formation of the first stars ends the dark ages of the universe, followed by the formation of galaxies. Image credit: M. Weiss/Harvard – Smithsonian Center for Astrophysics.
The Dark Energy Survey (DES) was carried out using a 570 megapixel energy-enhanced dark energy camera (decam) mounted on the NSF Víctor M. Blanco 4-M telescope from the NSF Neuroab program, Cerro Tololo Inter-American Observatory.
By obtaining data of 758 nights over six years, DES scientists mapped almost one-eighth area of the sky.
The project employs multiple observation techniques, including supernova measurement, galaxy clustering analysis, and weak gravity lenses, to study dark energy.
Two important DES measurements, baryon acoustic vibration (BAO) and explosive star distance measurements (type IA supernova) track the enlarged history of the universe.
Bao refers to a standard cosmic ruler formed by early universe sound waves, with peaks spanning approximately 500 million light years.
Astronomers can measure these peaks over several periods of universe history to see how dark energy has expanded the scale over time.
“By analyzing 16 million galaxies, DES discovered that the measured BAO scale is actually 4% smaller than predicted by λCDM,” says Dr. Santiago Avila, an astronomer at the Center for Energy and Environmental Technology Research (CIEMAT).
Type IA supernova acts as a standard candle. In other words, the essential brightness is known.
Therefore, its apparent brightness is combined with information about the host's galaxy to allow scientists to perform accurate distance calculations.
In 2024, the DES team released the most extensive and detailed supernova dataset to date, providing highly accurate measurements of space distance.
New discoveries from the combined supernova data and BAO data independently confirm the anomalies seen in the 2024 supernova data.
By integrating DES measurements with cosmic microwave background data, researchers infer the properties of dark energy, and the results suggest that they evolve time.
When verified, this implies a dynamic phenomenon in which the cosmological constant, dark energy, is not ultimately constant and requires a new theoretical framework.
“The results are interesting as they suggest physics beyond the standard models of cosmology,” says Dr. Juan Mena Fernandez, a researcher at the Institute of Subatomic Physics and Cosmology.
“If more data supports these findings, we may be on the brink of a scientific revolution.”
Although current results are still inconclusive, future analyses incorporating additional DES probes such as Galaxy Clustering and weak lenses could enhance the evidence.
Similar trends have emerged from other major cosmological projects, such as Dark Energy Spectroscopy (DESI).
“We've seen a lot of experience in our research,” said Jesse Muir, a researcher at the University of Cincinnati.
“There's still a lot to learn and it's exciting to see how understanding evolves as new measurements become available.”
Team's paper It will be published in journal Physical Review d.
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TMC Abbott et al. (DES collaboration). 2025. Dark Energy Survey: Final Devalion Acoustic Vibrations and Impact on Cosmological Expansion Models from Supernova Data. Physical Review din press; Arxiv: 2503.06712
Source: www.sci.news
