Astronomers measure expansion history of Universe with highest precision ever

Using the first-year survey data from the Dark Energy Spectroscopic Instrument (DESI), astronomers claim to have measured the expansion history of the Universe with the highest precision ever, providing an unprecedented look at the nature of dark energy - the unknown ingredient responsible for accelerating the Universe's expansion.

DESI, an international science collaboration of more than 900 researchers from over 70 institutions around the world, is conducting a five-year survey to create the largest 3D map of the Universe ever. The instrument, mounted on the U.S. National Science Foundation Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory, collects light from millions of galaxies across more than a third of the entire sky.

DESI's first-year data have allowed astronomers to measure the expansion rate of the Universe out to 11 billion years in the past, when the Universe was only a quarter of its current age, with a precision better than 1%.

"The DESI instrument has transformed the Mayall Telescope into the world’s premier cosmic cartography machine. The DESI team has set a new standard for studies of large-scale structure in the Universe. These first-year data are only the beginning of DESI's quest to unravel the expansion history of the Universe and they hint at the extraordinary science to come," says Pat McCarthy, Director of NOIRLab.

Astronomers looked 11 billion years into the past using Baryon Acoustic Oscillations (BAO) - the leftover imprint of pressure waves that permeated the early Universe when it was a hot, dense soup of subatomic particles. As the Universe expanded and cooled the waves stagnated, freezing the ripples in place and seeding future galaxies in the dense areas. This pattern is visible in DESI's detailed map, which shows strands of galaxies clustered together, separated by voids where there are fewer objects.

The researchers are awaiting the completion of the DESI project to confirm these findings.

"We are delighted to see cosmology results from DESI's first year of operations. DESI continues to amaze us with its stellar performance and how it is shaping our understanding of dark energy in the Universe," says Gina Rameika, associate director for High Energy Physics at the Department of Energy.