The Milky Way sits at the center of our attention, but it’s also the messy foreground the universe insists on putting in the way. And now, after five years, the Dark Energy Spectroscopic Instrument—DESI, working out of Kitt Peak National Observatory in Arizona—has finished a survey of the sky that captured more than 47 million galaxies and quasars.
This is being billed as the most detailed map of the universe ever made, and Misryoum’s newsroom reporting points to why it matters: those faint, far-off fingerprints can be used to test how the cosmos has expanded over time. Researchers are especially focused on an unsettling hint from earlier DESI results—an apparent weakening of dark energy—that could shake up the standard model of cosmology.
DESI has been scanning the sky since 2021, and the timeline didn’t go exactly as planned. The team originally expected the survey to gather data on 34 million galaxies and quasars. Instead, Misryoum newsroom reported that DESI proved more efficient than expected—so much so that some extremely faint galaxies were observed from just 100 or 200 photons. That detail sounds almost unreal, like trying to identify a singer from a whisper.
David Schlegel at the Lawrence Berkeley National Laboratory in California put the scale in context. Misryoum editorial desk noted that previous maps of the cosmos include a total of 5 million galaxies, so DESI’s data increases knowledge of the universe by a factor of almost 10. In his framing, astronomy seems to follow a rhythm: “We’ve actually been on this curve now for my whole career where, every 10 years, we’re making 10-times-larger maps,” he said. “You can ask the question, at what point have you mapped every observable galaxy within 10 billion light years… and if we stayed on the curve, we would do that by 2061.” Even if you don’t take that projection literally, it captures the momentum—and the appetite.
The main survey is complete, but there’s still a lag between collecting photons and getting conclusions. Misryoum analysis indicates the data will take another year to analyse before it is made available to researchers. Meanwhile, the project will continue to collect data for at least another two and a half years, and Schlegel said there are hopes DESI can be upgraded and kept running well into the 2030s. “This is still the leading instrument like it in the world,” he says, which also sounds a bit like a dare to whatever comes next.
In terms of coverage, the map now spans 14,000 square degrees of the sky, though the team hopes to expand that to 17,000 square degrees. The full sky has over 41,000 square degrees, but much of it is hard to observe because relatively close and bright objects—like the Milky Way—complicate things. Misryoum newsroom reported that the survey includes galaxies and quasars both above and below the plane of the Milky Way, with Earth at the centre—an awkward perspective that’s actually crucial for making the survey workable.
Scientists will use the data to compare how galaxies were distributed in the distant past and today, hunting for clues about dark energy, which makes up about 70 per cent of the universe. An earlier dataset from DESI in 2024 suggested dark energy, rather than remaining constant as expected, is weakening over time. If that weakening is real, Misryoum editorial team stated it would have profound implications for lambda-CDM, the standard model of cosmology. And with a full set of DESI data, researchers will be able to investigate that phenomenon further—though the universe rarely makes these questions easy.
Ofer Lahav at University College London added a personal note, the kind you only get from someone who has watched the field transform in real time. Misryoum newsroom reported that having access to the latest map from DESI would have seemed like science fiction early in his career. “When I was a PhD student in Cambridge, 40 years ago, we had a sample of thousands of galaxies. The community was starving for data,” he says.
“I think my students [today] may have the opposite problem; to have been flooded with data, and it’s very challenging to analyse it.” There’s a faint smell of dust in old archives, if you’ve ever been near one, and that’s the vibe—except now it’s servers humming instead of paper. With so much data, Misryoum analysis indicates there will be breakthroughs about the nature of the universe, but it’s also possible the team has already caught
unusual one-off cosmological incidents—those rare, weird signals that don’t repeat neatly, but still send you down a new path. And then, maybe, back again to dark energy, because it’s hard not to.
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