Results from global collaboration raise questions about future of universe

New results from the international Dark Energy Spectroscopic Instrument (DESI) collaboration, which includes researchers from Harvard, suggest that dark energy, widely thought to be a “cosmological constant,” might be weakening over time. This suggests the standard model of how the universe works may need an update.

The fate of the universe hinges on the balance between matter and dark energy, which is the force thought to be driving the universe’s accelerating expansion. DESI tracks dark energy’s influence by studying how matter is spread across the universe. The new analysis, using the largest 3D map of our universe ever made, looked at dark energy’s influence over the past 11 billion years.

The results, using the first three years of collected DESI data, were announced in a March 19 press release from the Lawrence Berkeley National Laboratory.

Events in the very early universe left subtle patterns in how matter is distributed, a feature called Baryon Acoustic Oscillations. That pattern acts as a standard ruler, with its size at different times directly affected by how the universe is expanding. Measuring the ruler at different distances shows researchers the strength of dark energy throughout history.

Combining the data of more than 14 million galaxies and quasars with the results from other experiments, scientists have stronger evidence that the impact of dark energy may be evolving in unexpected ways.

The Center for Astrophysics | Harvard & Smithsonian (CfA) researchers, led by Harvard Professor Daniel Eisenstein and his group, were crucial contributors to the DESI collaboration in multiple ways, including co-developing algorithms and simulations that led to the latest results.

Cristhian Garcia Quintero is one of the collaboration leads on the cosmological interpretations of the results. Michael Rashkovetskyi performed calculations that are critical for the distance measurements. Claire Lamman is the co-chair of the DESI education and public outreach committee and helped create the visual material for the public. Eisenstein served as co-spokesperson of the collaboration from 2014 to 2020. 

DESI involves more than 900 researchers from over 70 institutions around the world and is managed by the U.S. Department of Energy’s Berkeley Lab. The collaboration shared its findings in multiple papers to be posted on the online repository arXiv and in a presentation at the American Physical Society’s Global Physics Summit in Anaheim, California.

Alongside unveiling its latest dark energy results at the summit, the DESI collaboration also announced that its Data Release 1 is now available for anyone to explore. With detailed information on many millions of celestial objects, the data set will support a wide range of astrophysical research at CfA and elsewhere.

In addition to contributing to DESI’s cosmology goals, CfA researchers are using the collaboration to study galaxy evolution, the cosmic web, and the structure of the Milky Way. The DESI survey continues each clear night, extending its map of the cosmos and giving astronomers a continually improving view of the physics of the Universe.