Lost
Light

Background

Astronomers have reported the discovery of tens of thousands, or more, of brief flashes on old photographic plates taken before the launch of the first human-made satellite. These transients are sometimes found clustered together, and occasionally in apparent alignments or narrow bands. Their morphologies are consistent with sub-second timescales and with what would be expected from specular reflections of sunlight off flat, mirror-like material. Furthermore, they disappear in the Earth's shadow, correlate with nuclear tests and unidentified aerial phenomena, and show an anticorrelation with geomagnetic storm activity. While some astronomers continue to argue that these unusual flashes might be plate defects with star-like shapes or cosmic ray events, others have, using coma aberrations caused by faulty optics, demonstrated that at least a significant fraction of these objects originate from light emitted by astronomical sources passing through the telescope optics. Tentative results suggest that at least tens of thousands of these flat, reflective objects are in Earth's orbit. If these findings are confirmed and withstand independent scrutiny, we stand before one of the most unsettling and groundbreaking discoveries of our time.

We invite observatories around the world that host historical pre-Sputnik photographic plate collections to investigate the transient phenomenon together with us and independently validate and replicate the published findings. This is a global scientific question, one that concerns all of humanity, and it should therefore be explored using as many independent national plate archives as possible.

By comparing results across multiple archives, we aim to establish the robustness of the reported findings, quantify any systematic differences between observatories, and enable independent multi-observatory confirmation of transient candidates.

The next major discovery about our place in the Universe may already have been recorded on photographic plates that have remained unexplored for decades.

Mission statement

To ensure the comprehensive preservation of the world's archival astronomical images as part of our shared scientific and cultural heritage, to facilitate the discovery of historical astronomical phenomena, and to promote the systematic exploration of the transient phenomenon, its properties, and its reported correlates.

Why now?

Modern astronomical surveys reveal the sky as it is today. Only historical photographic plates preserve the unique record of transient events that occurred before the Space Age and were never observed again, capturing a sky that was still free from human-made satellites and orbital debris. Yet these photographic emulsions continue to deteriorate with time, whether or not we act.

Over the past few years, evidence has emerged suggesting that tens of thousands of short-duration transients may be present in archival photographic plate collections worldwide. Independent investigations have begun to replicate several key findings, but the phenomenon has so far been studied using only a handful of archives. Establishing whether these reported characteristics are universal, observatory-dependent, or the result of unknown systematic effects requires a coordinated international effort involving many independent plate collections.

Beyond its scientific objectives, such an effort also provides a compelling motivation for the long-term preservation and digitization of historical photographic plate collections. The resulting digital archives will remain a valuable resource for a broad range of future astronomical investigations extending far beyond the transient phenomenon itself.

The opportunity is unique. Unlike modern surveys, the photographic plate archives preserve observations from an era that can never be recreated. If these brief flashes are ultimately shown to be real specular reflections from objects in Earth's orbital environment, the evidence already exists. It is simply waiting to be discovered in photographic plate archives around the world.

What we hope to achieve

• Detect and catalogue all appearing and vanishing sources in historical photographic plate collections.
• Search for pre-Sputnik objects and their associated transient flashes.
• Perform multi-archive studies of the transient phenomenon, including parallax measurements where possible.
• Independently replicate the reported Earth shadow deficit at geosynchronous altitude (~42,000 km), as well as reported correlations with historical nuclear tests, Unidentified Aerial Phenomena (UAP), and geomagnetic storm activity. Investigate hotspots and how (if) they correlate with nuclear tests.
• Identify transients and multiple-transient events exhibiting coma aberrations.
• Further characterize the transient phenomenon across different observatories, geographical locations, observing epochs, instrumentation, and observing conditions.
• Investigate transient clustering in relation to the locations of historical nuclear tests.
• Develop a comprehensive understanding of the prevalence, characteristics, and underlying conditions of the pre-Sputnik transient phenomenon.

How your observatory can participate

1. If needed, digitize your historical photographic plate collection and make the digitized images publicly accessible.
2. Extract single-epoch point sources (transients) from your digitized images using the criteria described below or your own methods. We provide codes for effective transient detection.
3. Publish your transient catalogue, metadata, and scientific results openly. Deposit all manuscripts on arXiv and submit them to a peer-reviewed journal to ensure transparency, reproducibility, and independent scientific evaluation.
4. Compare your results with those from other participating observatories to identify common patterns, systematic differences, and observatory-specific effects.
5. Replicate previously published analyses using your own archive and explore new scientific questions related to the transient phenomenon.
6. Contribute your findings to the Project Lost Light collaboration and help establish an international framework for the independent verification and scientific exploration of the pre-Sputnik transient phenomenon.

How the challenge works

The challenge is open to professional research groups and to citizen scientists. Registration and all submissions are handled on ResearchHub.

A short letter of intent is reviewed first. Invited teams then submit a full pre-registration covering the transient detection strategy, statistical methods, error estimation, normalization procedures, choice of control samples, data binning, and any other relevant methodological decisions. The review is meant to improve methodological quality and reproducibility, not to approve, reject, or influence the scientific conclusions.

Before preparing a study or a pre-registration, teams are expected to read the Recommendations for future replication efforts and follow them. The pre-registration should describe the transient definition, the sample selection, the control sample, and the normalization methods in full detail.

Before any analysis, teams register their transient sample and coverage map (or a checksum of the sample) with a timestamp. The data submitted at the end must match the registered sample.

Accepted teams are notified after the pre-registration review and have nine months to submit a report together with their transient lists, code, and access to the image directory. Teams digitizing a new collection receive an additional six months.

An independent prize committee judges how well the pre-registered plan was carried out, from proposal to submission for peer review. Code should regenerate every reported figure from the public data. Null and refuting results are equally eligible. Papers do not need to be accepted for publication, but submission to a peer-reviewed journal is required for the top awards.

Three research awards are available, open equally to professional research groups and citizen scientists, with support for publication costs. Awards are paid on completion. All funds are administered by ResearchHub.

Additional funds raised through crowdfunding will go toward reviewer support and a further award for methodological originality.

Criteria

• Transient searches should be based on pairs of images of the same field obtained during a single night. At later stages of the project, comparisons between images of the same field obtained with the same filter at different epochs are strongly recommended.
• The required sky coverage depends on the scientific question being addressed. Investigations of the Earth shadow deficit require homogeneous sky coverage, whereas studies of the reported correlations with historical nuclear tests and Unidentified Aerial Phenomena do not.
• The fraction of transients located within the Earth's shadow at a geosynchronous altitude of approximately 42,000 km should be investigated. Earth shadow analyses should account for the empirical sky coverage of the observations and compare the observed transient distribution with randomly generated control samples, following the methodology of Bruehl et al. (2026), Section 8. Control samples based on stars are not recommended, as their spatial distribution is affected by Galactic extinction and other astrophysical selection effects. Detailed methodological recommendations will be published alongside the code before the challenge opens.
• All observations should have accurately documented timestamps and exposure times. The transient sample should provide sufficient statistical power for the scientific question being addressed. Initial searches should be restricted to optical images with exposure times of 30 minutes or longer, preferably obtained with telescopes of at least 0.8 m aperture.
• Detection rates may vary between observatories owing to differences in geographical location, instrumentation, observing strategies, and other factors that have yet to be characterized.

Rules

• Participants may identify transient candidates using either existing published methods or independently developed algorithms, provided that the optical selection criteria described in Solano et al. (2022) and Villarroel et al. (2026) are followed.
• A reference transient detection pipeline will be made available to participating observatories as an optional implementation.
• Independent analyses by each participating observatory are strongly encouraged.
• All publications arising from this initiative are expected to include an acknowledgment of Project Lost Light in the Acknowledgments section of the manuscript.
• Participants can withdraw at any time and proceed with the same project through the classical channels of their own choice.
• Researchers who have already published peer-reviewed studies on the Palomar transient phenomenon are not eligible to participate in this initiative.
• The pre-registration proposal and the final report are strongly encouraged to be written manually.

Data security and transparency

Participating observatories are responsible for maintaining the security, integrity, and long-term preservation of their own data. Offline archival copies of all FITS files and appropriate version control should be maintained throughout the data processing pipeline to ensure traceability and reproducibility. Once scientific analyses have been completed, transient catalogues, metadata, and scientific results should be made openly available in accordance with the principles of transparent and reproducible science.

Resources

DSS plate scans are provided by STScI for research and educational use only and may not be redistributed; see the MAST data use policy and cite the surveys as described on the MAST acknowledgments page. STScI plans to move the DSS archive to the MAST Amazon S3 bucket and to correct known errors in the image metadata (a small number of headers with incorrect astrometry, and more with incorrect observation dates and times) in the coming months. Both the plate list and the FITS headers will change; teams should record which version they used.

References

• Bruehl, S. & Villarroel, B. (2025). Transients in the Palomar Observatory Sky Survey (POSS-I) may be associated with nuclear testing and reports of unidentified anomalous phenomena. Scientific Reports, 15, 34125.
• Bruehl, S., Doherty, B., Streblyanska, A. & Villarroel, B. (2026). Use of machine learning to enhance detection of transient astronomical phenomena in historical observatory images. Scientific Reports, 16, 31890. doi:10.1038/s41598-026-66148-2
• Busko, I. (2026). Searching for Fast Astronomical Transients in Archival Photographic Plates. arXiv:2603.20407.
• Busko, I. (2026). Fast Astronomical Transients in Archival Photographic Plates: Using optical aberrations as a tool for discerning real images from plate artifacts. The Open Journal of Astrophysics, 9. doi:10.33232/001c.172381
• Cann, K. (2026). Geomagnetic storm suppression of photographic plate transient detections in the POSS-I archive: an independent physical variable strengthening the nuclear test correlation. arXiv:2604.04950.
• Cann, K. (2026). Storm-Driven Suppression and Post-Storm Enhancement of Photographic Plate Transient Detections at Geosynchronous Altitude: Empirical Evidence and a Candidate Dusty Plasma Mechanism. arXiv:2604.06234.
• Cann, K. (2026). Plate Sensitivity Is Invariant Across Geomagnetic Storm Intensity at Two Independent Observatories: Ruling Out the Airglow Artifact and Confirming Source-Specific Transient Suppression. ESS Open Archive, 2026, 0416.
• Doherty, B. (2026). Independent Replication of Nuclear Test-Transient Correlations and Earth Shadow Deficit in POSS-I Photographic Plates. arXiv:2604.00056.
• Doherty, B. (2026). Statistically Significant Linear Alignments Among High-Confidence Transient Candidates on POSS-I Photographic Plates. arXiv:2605.01190.
• Solano, E., Villarroel, B. & Rodrigo, C. (2022). Discovering Vanishing Objects in POSS I Red Images Using the Virtual Observatory. MNRAS, 515, 1380-1391.
• Solano, E., Marcy, G. W., Villarroel, B., et al. (2024). A bright triple transient that vanished within 50 min. MNRAS, 527, 6312-6320.
• Villarroel, B., Marcy, G. W., Geier, S., et al. (2021). Exploring Nine Simultaneously Occurring Transients on 12 April 1950. Scientific Reports, 11, 12794.
• Villarroel, B., Mattsson, L., Guergouri, H., et al. (2022). A Glint in the Eye: Photographic Plate Archive Searches for Non-terrestrial Artefacts. Acta Astronautica, 194, 106-113.
• Villarroel, B., Pelckmans, K., Solano, E., et al. (2022). Launching the VASCO Citizen Science Project. Universe, 8, 561.
• Villarroel, B., Solano, E., Guergouri, H., et al. (2022). Is There a Background Population of High-Albedo Objects in Geosynchronous Orbits around Earth? arXiv:2204.06091.
• Villarroel, B., Watters, W. A., Streblyanska, A., et al. (2026). A cost-effective search for extraterrestrial probes in the Solar system. MNRAS, 546, staf1158.
• Villarroel, B., Solano, E., Guergouri, H., et al. (2025). Aligned, Multiple-transient Events in the First Palomar Sky Survey. PASP, 137, 104504.
• Villarroel, B., Soodla, J., Comeron, S., et al. (2020). The Vanishing & Appearing Sources during a Century of Observations (VASCO): A Pilot Search for Vanishing Objects. AJ, 159, 8.
• Villarroel, B., Solano, E. & Marcy, G. W. (2025). On the Image Profiles of Transients in the Palomar Sky Survey. arXiv:2507.15896.
• Villarroel, B. & Marcy, G. (2023). A New Era of Optical SETI: The Search for Artificial Objects of Non-Human Origin. The Debrief.
• Villarroel, B., Streblyanska, A., Bruehl, S. & Geier, S. (2026). A Response to "Critical Evaluation of Studies Alleging Evidence for Technosignatures in the POSS1-E Photographic Plates" by Watters et al. (2026). arXiv:2602.15171.