Unprecedented discovery: the dark energy of the Universe could change over time

GenevaDark energy fills the entire Universe and determines its expansion rate. Now, data from more than 15 million galaxies and quasars, the DESI (Dark Energy Spectroscopic Instrument) experiment, in which Catalonia participates heavily, reveal that this type of energy could have varied over time.

Although it is still too early to speak of a revolution in our view of the Universe, the results suggest that the current model describing the cosmos needs a profound overhaul. "The results obtained seem to indicate that we are on the verge of witnessing a paradigm shift in models of the evolution of the Universe," comments Andreu Font-Ribera, a scientist at the Institute of High Energy Physics (IFAE) and a member of the DESI team.

A 3D map of the Universe

The origin of dark energy is still unknown, but it causes the Universe to expand ever more rapidly. Current models assume that dark energy is constant, meaning it neither increases nor decreases over time. The balance between dark matter and dark energy present will determine the fate of the Universe, which could continue to expand forever or collapse in on itself. Therefore, it is essential to measure its concentration with great precision.

To answer this question, the DESI collaboration is creating the largest 3D map of the cosmos. The instrument, capable of capturing light from 5,000 galaxies simultaneously, is installed on the Nicholas U. Mayall Telescope at Kitt Peak National Observatory in Arizona. During its five years of operation, DESI is expected to collect data on nearly 50 million galaxies and quasars.

Although the DESI results in isolation are consistent with the standard model of the Universe, known as lambda-CDM, when combined with data from other cosmological experiments, indications emerge that dark energy could weaken over time. This positions alternative models to better describe the evolution of the cosmos. "We are at a very exciting moment because we have realized that there are aspects of the Universe that we still do not fully understand," explains Laura Casas, a doctoral student at IFAE.

An open destiny

DESI is an international experiment led by the Lawrence Berkeley Laboratory in the United States. It involves more than 900 researchers from over 70 institutions around the world, with significant contributions from Catalan research groups. These include the UB's Institute of Cosmos Sciences (ICCUB), the Institute of Space Sciences (ICE-CSIC), and the Institute of High Energy Physics (IFAE). These groups have been key players in the analysis of the data collected by the telescope.

The data analyzed were collected during DESI's first three years of operation. The collaboration will continue to analyze and collect new data over the coming years to increase the precision of the measurements. "The observational results obtained open up a wide range of possible explanations," says Francisco Javier Castander, a researcher at the Institute for Space Studies who contributed to the experiment: "Regardless of the nature of dark energy, its properties will determine the future of the Universe."