Milan, Italy · 15 October 2024 — The European Space Agency has released the first installment of its great cosmic atlas, a stunning 208-gigapixel mosaic that represents the opening page of the Euclid space telescope's ambitious six-year survey to unravel the mysteries of dark matter and dark energy.
The mosaic was unveiled at the International Astronautical Congress in Milan by ESA Director General Josef Aschbacher and Director of Science Carole Mundell, offering a breathtaking glimpse of the southern sky captured between March and April 2024.
A Glimpse of the Invisible Universe
Euclid's first cosmic atlas page covers 132 square degrees of the southern sky — an area more than 500 times the size of the full Moon as seen from Earth. Despite its immense scale, this mosaic accounts for just 1% of the total survey area that Euclid will map over its six-year mission.
The data combines inputs from Euclid's two primary scientific instruments: the VIS (visible light camera), which images the shapes of billions of galaxies with exquisite precision, and the NISP (Near-Infrared Spectrometer and Photometer), which measures the distances to those galaxies by analyzing their infrared light.
The Dark Universe Problem
Dark matter and dark energy together account for approximately 95% of the universe's total mass-energy content, yet neither has been directly observed. Dark matter, which exerts gravitational pull on visible matter, makes up about 27% of the cosmos. Dark energy, the mysterious force driving the accelerated expansion of the universe, constitutes roughly 68%.
Euclid aims to shed light on these invisible components by measuring the shapes and distances of billions of galaxies across cosmic time. By observing how dark matter bends the light of distant galaxies — a phenomenon known as weak gravitational lensing — and how dark energy drives the universe's expansion, scientists hope to determine whether dark energy is a cosmological constant or whether it evolves over time.
From Survey to Science
Euclid launched on 1 July 2023 aboard a SpaceX Falcon 9 rocket from Cape Canaveral, Florida, and arrived at its observing position at the Sun-Earth Lagrange point L2, approximately 1.5 million kilometers from Earth, about a month later. After a commissioning phase that included resolving an issue with stray light affecting the VIS instrument, Euclid began its routine science survey in February 2024.
By the time of the October 2024 mosaic release, the telescope had already completed approximately 12% of its total survey. The mission's primary objective is to create a 3D map covering one-third of the sky, observing billions of galaxies out to redshift z ~ 2, corresponding to lookback times of up to 10 billion years.
Early Science Results
In May 2024, the Euclid consortium published the first set of science results from its Early Release Observations (ERO) program. These included high-resolution images and accompanying scientific papers showcasing the telescope's ability to observe diverse targets — from star-forming regions in the Milky Way to distant galaxy clusters — demonstrating its readiness for the main survey.
| Euclid Instrument | Function | Wavelength Range |
|---|---|---|
| VIS (Visible Imager) | Galaxy shape measurement | 550–900 nm |
| NISP (Near-Infrared Spectrometer and Photometer) | Galaxy distance measurement | 920–2020 nm |
The Road Ahead
The first comprehensive catalogue of astronomical data, known as Quick Data Release 1 (Q1), was delivered to the scientific community in March 2025, providing a much deeper dataset for cosmological analysis. The mission's major cosmology results are expected to follow as the survey progresses toward completion around 2030.
"This is the first page of a cosmic atlas that will ultimately map the entire dark universe. What we are seeing is just 1% of the survey, and it is already breathtaking. Imagine what the full atlas will reveal."
The Euclid consortium involves more than 2,000 scientists from over 300 institutions across 15 European countries, the United States, Canada, and Japan, making it one of the largest collaborative space science endeavours ever undertaken.
Sources:
- ESA, Euclid's First Cosmic Atlas Page (esa.int, 15 October 2024)
- NASA, New Images from Euclid Mission (nasa.gov)
- UCL, First Page of Euclid's Cosmic Atlas Revealed (ucl.ac.uk, October 2024)
- Euclid Consortium, Early Release Observation Science Papers (euclid-ec.org)
- Max Planck Institute, Euclid Data Release (mpg.de)
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