A landmark achievement in modern science has been reached with the completion of the largest ever three dimensional map of the Universe this week, a feat that promises to deepen humanity’s understanding of the mysterious force driving cosmic expansion.
The project, led by the Dark Energy Spectroscopic Instrument, DESI, marks a defining moment in cosmology, with strong and enduring contributions from the United Kingdom’s world leading scientific community.
The milestone was achieved when DESI’s 5,000 fibre optic sensors captured their final scheduled observations, focusing on a region of sky near the Little Dipper. The survey finished ahead of schedule and delivered significantly more data than originally expected, underscoring both the ambition and precision of the international collaboration.
Chasing dark energy
At the heart of this effort lies one of the greatest scientific mysteries, dark energy, the force believed to make up roughly 70 per cent of the Universe and responsible for its accelerating expansion.
By comparing how galaxies clustered billions of years ago with how they are distributed today, researchers have traced dark energy’s influence across 11 billion years of cosmic history. Early findings from the first three years of DESI data suggested that dark energy, long assumed to be constant, may in fact be evolving over time.
With the full five year dataset now complete, scientists have a far richer foundation to test this possibility, one that could fundamentally reshape our understanding of the Universe and its ultimate fate.
Professor Ofer Lahav of University College London, a key figure in the project, said:
“This is a very exciting milestone.”
“The data-gathering phase has far exceeded expectations.”
“DESI observations processed so far suggest the intriguing possibility that the density of dark energy may evolve over time.”
“The collaboration will now analyse the full dataset to test this result, as its confirmation would represent a paradigm shift in our understanding of the universe.”
A proud British contribution
The United Kingdom has played a pivotal role in this global scientific endeavour, supported by the Science and Technology Facilities Council, STFC, and driven by leading universities across the country.
Durham University has been central to the mission, with Dr Willem Elbers leading major aspects of the analysis, including work to determine the mass of neutrinos, fundamental particles that form part of the Universe’s dark matter.
University College London contributed from the very beginning, with its instrumentation team, led by Peter Doel, designing and building DESI’s sophisticated optical corrector, a system of six lenses up to 1.1 metres in diameter that focuses light for detailed spectroscopic study.
Meanwhile, the University of Portsmouth has been instrumental in extracting key measurements, with Associate Professor Seshadri Nadathur co chairing the galaxy and quasar clustering working group.
Professor Carlos Frenk of Durham University reflected on the scale of the achievement:
“Only 10 years ago, I would have thought that measuring the rate at which the Universe expands with an accuracy of one percent was just fantasy.”
“Yet DESI has done it!”
“The amount and quality of the DESI data, and the analysis carried out by an international team of very talented scientists, are behind this achievement.”
“The rewards are huge: the data suggest an unexpected behaviour of dark energy that may upturn the currently accepted view of how our Universe evolves.”
A dataset on an unprecedented scale
DESI has gathered cosmological data from six times as many galaxies and quasars as all previous surveys combined, observing more than 47 million galaxies and quasars alongside 20 million stars.
This immense dataset is expected to yield fresh discoveries for years to come. The first full results from the five year survey are anticipated in 2027, while further studies based on earlier data are due later this year.
Associate Professor Nadathur emphasised the significance of the achievement:
“It is hard to overstate how important this DESI map of galaxies will be for cosmology.”
“The possibility of dark energy evolving with time would be revolutionary on its own, and there are still many other things we can do with the data, including weighing neutrinos, the lightest known fundamental particles.”
“We’ve barely scratched the surface so far, and I’m excited to see what else we can learn.”
A new era of discovery
Since beginning observations in May 2021, DESI has far exceeded its original ambitions, capturing far more data than planned and continuing to expand its survey into new regions of the sky.
The project will now push even further, extending its map and refining measurements to create an even more detailed picture of how the Universe has evolved.
Dr Michael Levi, DESI director, summed up the achievement:
“DESI’s five-year survey has been spectacularly successful.”
“The instrument performed better than anticipated.”
“The results have been incredibly exciting.”
“And the size and scope of the map and how quickly we’ve been able to execute is phenomenal.”
As Britain’s scientists continue to play a leading role in analysing this extraordinary dataset, the nation stands firmly at the cutting edge of a new cosmic era, one that may yet redefine humanity’s place in the Universe.
