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The revolution in strong lensing discoveries from Euclid

Nature Astronomy volume 9, pages 1116–1122 (2025)Cite this article

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Abstract

Strong gravitational lensing offers a powerful and direct probe of dark matter, galaxy evolution and cosmology, yet strong lenses are rare: only 1 in roughly 10,000 massive galaxies can lens a background source into multiple images. The European Space Agency’s Euclid telescope, with its unique combination of high-resolution imaging and wide-area sky coverage, is set to transform this field. In its first quick data release, covering just 0.45% of the full survey area, around 500 high-quality strong lens candidates have been identified using a synergy of machine learning, citizen science and expert visual inspection. This dataset includes exotic systems such as compound lenses and edge-on disk lenses, demonstrating Euclid’s capacity to probe the lens parameter space. The machine learning models developed to discover strong lenses in Euclid data are able to find lenses with high purity rates, confirming that the mission’s forecast of discovering over 100,000 strong lenses is achievable during its 6-year mission. This will increase the number of known strong lenses by two orders of magnitude, transforming the science that can be done with strong lensing.

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Fig. 1: An Einstein ring embedded in the nearby galaxy NGC 6505 imaged by Euclid.
Fig. 2: The density of strong lenses against the survey area for different lens searches.
Fig. 3: An example strong lens found in a Euclid tile.
Fig. 4: Examples of strong lenses discovered in Euclid Q1.
Fig. 5: A mosaic of 12 Euclid lensed galaxies and their corresponding reconstructed sources.
Fig. 6: The different types of strong lenses found by the fine-tuned Zoobot model.

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Acknowledgements

Euclid is an ESA mission with major contributions from the Euclid Consortium, consisting of more than 2,000 scientists, engineers and technicians from 15 European countries, the USA, Canada and Japan.

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Authors and Affiliations

  1. Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK

    Natalie E. P. Lines, Tian Li, Thomas E. Collett & Karina Rojas

  2. Department of Physics, Oxford University, Oxford, UK

    Philip Holloway & Aprajita Verma

  3. School of Mathematics, Statistics and Physics, Newcastle University, Newcastle-upon-Tyne, UK

    James W. Nightingale

  4. School of Engineering, University of Applied Sciences and Arts of Northwestern Switzerland, Windisch, Switzerland

    Karina Rojas

  5. David A. Dunlap Department of Astronomy & Astrophysics, University of Toronto, Toronto, Ontario, Canada

    Mike Walmsley

  6. Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester, UK

    Mike Walmsley

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  1. Natalie E. P. Lines
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  2. Tian Li
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  3. Thomas E. Collett
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Contributions

N.L. led the structuring of the text, wrote the initial version of the manuscript and produced Figs. 3, 4 and 6. T.L. produced Fig. 1. M.W. produced Fig. 2. J.N. produced Fig. 5. All authors contributed to the research discussed, reviewed the full text and edited the manuscript.

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Correspondence to Natalie E. P. Lines.

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Lines, N.E.P., Li, T., Collett, T.E. et al. The revolution in strong lensing discoveries from Euclid. Nat Astron 9, 1116–1122 (2025). https://doi.org/10.1038/s41550-025-02616-5

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