70-Year-Old Palomar Plates Revisited: Mysterious Star‑Like Flashes Linked to Cold War Nuclear Tests — Scientists Debate

More than seven decades before the launch of Sputnik, astronomers at California’s Palomar Observatory photographed brief, star‑like flashes on glass photographic plates that appeared and vanished within an hour. A new, peer‑reviewed reanalysis of those mid‑20th‑century sky plates reports that many of these fleeting points of light — called transients — cluster around dates of Cold War aboveground nuclear tests and coincide with spikes in historical UFO (UAP) reports.

The study examined digitized scans of the first Palomar Observatory Sky Survey (POSS‑I), carried out between 1949 and 1958. That program used roughly 2,000 glass plates with 50‑minute exposures taken with the Samuel Oschin Schmidt Telescope, later scanned into a digital archive for modern analysis. The authors reviewed 2,718 observing days and identified transient signatures on 310 nights; in some cases they report thousands of flashes registered across different fields on a single day but absent from images taken immediately before or after and from later surveys.

Statistical associations and provocative questions

When the researchers compared transient detections with the UFOCAT database of historical reports, they found statistical associations: transients were about 45% more likely to appear within 24 hours of aboveground nuclear detonations conducted by the United States, the Soviet Union and Great Britain, and each additional UAP report on a given day corresponded to an estimated 8.5% increase in transient detections. The analysis, published Oct. 20 in Scientific Reports, describes these coincidences as "associations beyond chance," while clearly noting that correlation does not imply causation.

"We've ruled out some of the prosaic explanations, and it means we have to at least consider the possibility that these might be artificial objects from somewhere," said study co‑author Stephen Bruehl, an anesthesiologist at Vanderbilt University who has an ongoing interest in unidentified aerial phenomena. He and lead author Beatriz Villarroel of the Nordic Institute for Theoretical Physics highlight several events with sharp, point‑like appearances and apparent linear alignments that they argue are hard to reconcile with common photographic defects or known astrophysical sources.

Alternate explanations and expert skepticism

Many astronomers urge caution. Some point to well‑known natural and instrumental causes for transient detections — variable stars, meteors, cosmic rays, atmospheric flashes or quirks of the photographic process. Michael Wiescher, a nuclear astrophysicist, suggested that nuclear detonations can loft metallic fragments and radioactive dust into the upper atmosphere, producing brief glows that might register on telescopes.

Other experts emphasize archival and methodological limits. Michael Garrett of the Jodrell Bank Centre for Astrophysics praised the creative use of archival data but warned that pre‑Sputnik records and anecdotal UAP reports are notoriously hard to validate and that the underlying data quality is poor. Robert Lupton (Princeton) and Nigel Hambly (University of Edinburgh) note that aligned or linear patterns can arise from diffraction spikes around bright stars, dust, hair or debris on the emulsion, and scratches introduced during copying or digitization. Hambly adds that working from reproductions rather than original plates can preserve or amplify such defects across generations of scans.

The Palomar team considered these possibilities and argues the recorded transients often look like sharp, star‑like points rather than diffuse smudges. They also note that any physical fragments appearing motionless during a 50‑minute exposure would need to be at very high altitudes — roughly the altitude of geostationary orbit, about 22,000 miles (approximately 35,800 kilometers) — a scenario they call implausible without extraordinary intervention.

What’s next: forensic checks and independent replication

Most researchers interviewed about the findings agree on one point: independent reanalysis and direct inspection of the original plates are essential. Proposed next steps include reexamining the same digitized archives and other pre‑1957 plate collections from Northern Hemisphere observatories, and conducting microscopic, forensic inspections of the original Palomar plates to determine whether the transients appear on the originals or were introduced during copying or scanning. Visual inspection at high magnification can sometimes reveal blemishes lost in digital scans.

Whether these flashes ultimately prove to be unidentified anomalous phenomena, classified technologies, fallout effects, or artifacts of an old imaging process, the episode illustrates how science handles unexpected results: test, replicate, and seek higher‑quality data. As David Windt, a research scientist at Columbia University, observed, the debate could also help normalize careful, academic study of historical anomalies.