DESI Completes Five-Year Sky Survey Mapping Over 47 Million Galaxies and Quasars

The Dark Energy Spectroscopic Instrument (DESI) has completed its five-year survey of the sky, capturing data on more than 47 million galaxies and quasars, @NewScientist reported. The survey, which began in 2021, allows researchers to finalize the most detailed map of the universe ever made.

Located at Kitt Peak National Observatory in Arizona, DESI exceeded initial expectations by gathering data beyond the originally anticipated 34 million galaxies and quasars.

Some galaxies observed by DESI were detected from just 100 or 200 photons, highlighting the instrument's efficiency in capturing faint, distant objects. Previous maps of the cosmos included a total of 5 million galaxies, according to David Schlegel at the Lawrence Berkeley National Laboratory in California.

The DESI data increases knowledge of the universe by a factor of almost 10 compared to those earlier maps.

David Schlegel stated that every 10 years, maps of the universe have been made 10 times larger over his career. He added that if the trend continues, every observable galaxy within 10 billion light years would be mapped by 2061. The DESI main survey is now complete, but the data will take another year to analyze before it is made available to researchers.

The DESI project will continue to collect data for at least another two and a half years. Schlegel said there are hopes that DESI can be upgraded and kept running well into the 2030s. He described DESI as the leading instrument of its kind in the world.

DESI’s map covers 14,000 square degrees of the sky, with the team hoping to expand it to 17,000 square degrees. The full sky has over 41,000 square degrees. Dark energy makes up about 70 per cent of the universe, and an earlier DESI dataset from 2024 suggested that dark energy is weakening over time.

The DESI data will allow scientists to compare galaxy distributions in the distant past and today. Ofer Lahav at University College London stated that 40 years ago, as a PhD student in Cambridge, samples included thousands of galaxies. He noted that the community was starving for data back then, contrasting with today's abundance that challenges analysis.