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These strange apparitions, called gravitational lenses, occur when extremely massive objects, such as galaxies or galaxy clusters, warp spacetime. This distortion bends and amplifies the light from much more distant objects. These cosmic distortions remain exceptionally rare and difficult to spot among billions of astronomical data points.
An Einstein ring seen here by Hubble.
For astronomers, this quest is a daunting task. Even the most advanced machine-learning algorithms struggle to identify these subtle patterns in images of the sky. That is where human eyes come in, particularly adept at spotting unusual shapes that machines might miss. A new citizen science initiative invites the public to scrutinize unprecedented images from the European Space Agency's (ESA) Euclid space telescope to track down these distortions.
The project, called Space Warps and hosted on the Zooniverse platform, invites participants to examine real Euclid images. Around 300,000 snapshots, preselected by artificial intelligence, will be submitted to volunteers for judgment. These images represent the best candidates from 72 million galaxies observed during the mission's first data release. No scientific training is required: guides and examples help recognize gravitational lenses.
The scientific importance of this endeavor is considerable. Gravitational lenses act as cosmic magnifying glasses, allowing observation of extremely distant galaxies normally too faint to be detected. They also provide valuable clues about the distribution of dark matter in the Universe. By identifying these objects, volunteers help refine cosmological models and understand how visible and invisible matter is distributed on large scales.
Since its launch in 2023, Euclid has been mapping the large-scale structure of the Universe with unprecedented precision. The telescope transmits about 100 GB of data to Earth each day. Researchers estimate that volunteers could discover more than 10,000 new gravitational lens candidates, greatly expanding the current catalog. This work builds on previous successes of citizen science, which has already found hundreds of lenses.
Collage of Euclid images showing examples of gravitational lenses, where foreground objects distort the light from more distant objects into arcs or, in rare cases, complete Einstein rings.
Credit: ESA/Euclid/Euclid Consortium/NASA, image processing by M. Walmsley, M. Huertas-Company, J.-C. Cuillandre
The initiative illustrates a growing trend in astronomy: the largest datasets in history are now being explored not only by scientists and supercomputers, but also by anyone with an internet connection and a desire to contribute to discovery. The classifications made by volunteers also help improve the artificial intelligence systems used to process astronomical data, creating a beneficial synergy between humans and machines.
If you are interested in joining the hunt, it is here.
Why call on "amateurs"?
Image recognition algorithms, while effective, sometimes struggle to identify rare and subtle patterns like gravitational lenses. The human eye, trained to spot abnormal shapes, can detect candidates that machines miss. Citizen science projects like Space Warps harness this ability by mobilizing thousands of volunteers to examine large amounts of data.
This approach has already proven itself. For example, in March 2025, 500 strong lenses were discovered in just 0.04% of Euclid's data, thanks to volunteer help. These classifications not only enrich scientific databases but also serve to train and improve artificial intelligences.