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Cited by 117Astrophysical Phenomena and ObservationsGalaxies: Formation, Evolution, PhenomenaGamma-ray bursts and supernovae

Space Warps – I. Crowdsourcing the discovery of gravitational lenses

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Marshall, Philip J., Verma, Aprajita, More, Anupreeta, Davis, Christopher P., More, Surhud, Kapadia, Amit, Parrish, Michael, Snyder, Chris +14 more·2016·Monthly Notices of the Royal Astronomical Society
DOI 10.1093/mnras/stv2009
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Abstract

We describe Space Warps, a novel gravitational lens discovery service that yields samples of high purity and completeness through crowdsourced visual inspection. Carefully produced colour composite images are displayed to volunteers via a web-based classification interface, which records their estimates of the positions of candidate lensed features. Images of simulated lenses, as well as real images which lack lenses, are inserted into the image stream at random intervals; this training set is used to give the volunteers instantaneous feedback on their performance, as well as to calibrate a model of the system that provides dynamical updates to the probability that a classified image contains a lens. Low-probability systems are retired from the site periodically, concentrating the sample towards a set of lens candidates. Having divided 160 deg2 of Canada–France–Hawaii Telescope Legacy Survey imaging into some 430 000 overlapping 82 by 82 arcsec tiles and displaying them on the site, we were joined by around 37 000 volunteers who contributed 11 million image classifications over the course of eight months. This stage 1 search reduced the sample to 3381 images containing candidates; these were then refined in stage 2 to yield a sample that we expect to be over 90 per cent complete and 30 per cent pure, based on our analysis of the volunteers performance on training images. We comment on the scalability of the Space Warps system to the wide field survey era, based on our projection that searches of 105 images could be performed by a crowd of 105 volunteers in 6 d.

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  • Even the largest citizen science lens search projects have only inspected up to around one million images.

    “Even the largest citizen science lens search projects have only inspected up to around one million images (Marshall et al. 2015; More et al. 2016; Sonnenfeld et al. 2020; González et al. 2025).”

    From Euclid Quick Data Release (Q1): XXVIII. The Strong Lensing Discovery Engine C – Finding lenses with machine learning (2026) · cites this paper as Marshall et al. 2015

    The Conclusions report that Space Warps searched about 430,000 image tiles, supporting the claim’s approximate scale for this project. The paper does not establish that the largest citizen-science lens searches overall had inspected no more than around one million images; its discussion of a million targets describes a future possibility, not a completed search. (LLM, conf=0.82)

    Experimental — accuracy not yet measured

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Research works printed but not linked: 4

  1. Refregier A., Amara A., Kitching T. D., Rassat A., Scaramella R., Weller J., for the Euclid Imaging Consortium, 2010, preprint (arXiv:e-prints)
  2. Simpson R., Page K. R., De Roure D., 2014, in Proc. Companion Publication of the 23rd International Conf. on World Wide Web Companion, WWW Companion '14. Republic and Canton of Geneva, Switzerland, Interna- tional World Wide Web Conferences Steering Committee, p. 1049
  3. Waterhouse T. P., 2013, in Proc. CSCW, Pay By the Bit: An Information- Theoretic Metric for Collective Human Judgment. ACM New York, NY, p. 623
  4. Wherry N., Blanton M. R., Hogg D. W., 2004, preprint (arXiv:e-prints)

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Authors
Marshall, P. J., Verma, A., More, A., Davis, C. P., More, S., Kapadia, A., Parrish, M., Snyder, C., Wilcox, J., Baeten, E., Macmillan, C., Cornen, C., Baumer, M., Simpson, E., Lintott, C. J., Miller, D., Paget, E., Simpson, R., Smith, A. M., Küng, R., Saha, P., & Collett, T. E.
Affiliations
  • University of Oxford (GB)
  • Kavli Institute for the Physics and Mathematics of the Universe (JP)
  • Kavli Institute for Particle Astrophysics and Cosmology (US)
  • Adler Planetarium (US)
  • University of Zurich (CH)
  • University of Portsmouth (GB)
Corresponding author
Marshall, Philip J.
ORCID
Venue
Monthly Notices of the Royal Astronomical Society
Publisher
Oxford University Press (OUP)
Published
2015-11-10
Volume
455
Issue
2
Pages
1171-1190
ISSN
  • 0035-8711 (ISSN-L)
  • 1365-2966
DOI
10.1093/mnras/stv2009
OpenAlex
W1924089270
Cited by
117
References
50
Citations by year
2026: 11 · 2025: 9 · 2024: 12 · 2023: 5 · 2022: 12 · 2021: 7 · 2020: 12 · 2019: 16 · 2018: 10 · 2017: 12 · 2016: 10 · 2015: 1
FWCI
6.26
Type
journal article
Language
en
Open access
Locations
  • Monthly Notices of the Royal Astronomical Society (publishedVersion)
  • Zurich Open Repository and Archive (University of Zurich) (acceptedVersion, other-oa)
  • arXiv (Cornell University) (submittedVersion)
  • reroDoc Digital Library (submittedVersion)
  • HighWire Press Open Archive (submittedVersion)
  • Zurich Open Repository and Archive (University of Zurich) (submittedVersion, other-oa)
  • arXiv (Cornell University)
  • Zurich Open Repository and Archive (University of Zurich)
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Gamma-ray bursts and supernovae
Keywords
crowdsourcing, citizen science, lens candidate selection, wide-field survey, scalability

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