Discoveries
Modern exploration: DESI data and the strategy set at IAC
The largest 2D map of the universe meets the policy debate that decides what gets observed next: standardised catalogues, spectrographs and coordination.
In brief
The DESI Legacy Imaging Surveys, released on 10 August, is an unprecedented two-dimensional map of the sky. Read alongside the discussions at the International Astronautical Congress in Milan, it shows what is still missing to turn a huge dataset into science: standardised catalogue access, spectrograph capacity and international coordination.
Key points
- Use the Legacy Survey Sky Viewer to browse and inspect the DESI catalogues directly.
- Standardising catalogue access and data flows between observatories is the practical bottleneck.
- Spectrographs and fast spectroscopy capacity are what make follow-up observations possible.
- Forums such as the IAC are where data turns into mission priorities and funding decisions.
- Combining observations across observatories is how flat images become precise 3D maps.
Modern exploration of the cosmos advances on two fronts at once: the mass collection of data, and the international coordination that decides what to do with it. This article connects the largest two-dimensional map of the universe, released on 10 August, with the strategic discussions that emerged at the International Astronautical Congress in Milan. Neither half is much use without the other.
The map, and what it is for
The DESI Legacy Imaging Surveys has been online since 10 August. It is the most extensive two-dimensional map of the universe ever produced: it covers three quarters of the sky and includes a catalogue of nearly four billion celestial objects. It is the result of 263,407 telescope exposures, combined into a homogeneous mosaic of more than five trillion pixels. Images taken on different nights, under different atmospheric conditions, were made consistent by dedicated software.
The collection identifies faint objects and builds pointing catalogues for the DESI spectrograph. DESI, the Dark Energy Spectroscopic Instrument, measures redshift, the shift of light towards longer wavelengths, and from that determines the three-dimensional position of galaxies. Dark energy is what accelerates the expansion of the universe, and redshift is how its history is read.
More precise redshift measurements are what allow quantitative study of the expansion and of how matter is distributed, and therefore of how dark energy has shaped cosmic history.
Global collaboration to make sense of it
The map is freely consultable through the Legacy Survey Sky Viewer, which opens its catalogues to researchers and to the public alike. More than 160 scientists contributed to the data collection, and a team of 20 researchers produced the final result. Earlier releases of the surveys are already a daily tool for astronomers: they have generated over 1,800 scientific papers.
In parallel, the International Astronautical Congress was held in Milan, at Europe’s largest congress centre, from 14 to 18 October 2024. The event gathered more than 11,000 experts from industry, research institutes and space agencies. The European Space Agency had a central role, presenting Europe’s ambitions in space alongside the concrete steps to reach them. That forum is where scientific data becomes mission priorities and funding decisions.
From detail to the bigger picture
The DESI map is a valuable instrument for hunting rare phenomena. It makes it easier to identify gravitational lenses, where mass bends light, which in turn allows dark matter to be mapped: dark matter does not interact with light, and its presence is inferred from gravitational effects alone. The map also helps spot transient phenomena, such as supernovae, stellar explosions visible for weeks. The Sky Viewer lets you zoom into regions of the sky and click individual objects to reach the underlying data.
The discussions at the IAC underlined the operational need on the other side. To exploit this data properly, more pointing coordinates are required, along with fast spectroscopy and harmonised data flows, so that follow-up observations can actually be triggered. The expanded Legacy Surveys data will let DESI reach more distant galaxies and improve the precision of cosmological measurements. The plans discussed in Milan aim to capitalise on the datasets that already exist, rather than assume new ones.
The road ahead demands closer integration between observatories, standardised catalogue access, and funding for spectrographs and missions that turn pixels into more precise 3D maps.
The challenge remains connecting the vast availability of public data with the policy decisions taken in international forums. That connection is what allows modern exploration to keep turning images into a real understanding of the universe.
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