A new study analyzing historical photographs taken by the Palomar Observatory between 1949 and 1957 has detected several mysterious bright spots in the sky. These transient objects, captured on film before the first satellites were ever launched, appear to have occurred on dates that strongly correlated with nuclear weapons tests.
The observations were made by researchers from the Vanishing and Appearing Sources during a Century of Observations (VASCO) project. This initiative searches through archives of digitized historical and modern sky surveys for objects that have either disappeared completely or flashed briefly (transient) in the sky.
Transients are star-like objects that appear in one photo but are gone by the time the next photo of the same region of sky has been taken. Their origin is unknown, and proposed explanations range from small pieces of asteroids to photographic plate fragments and UAPs (unidentified anomalous phenomena, the new official name for UFOs).
For decades, anecdotal reports and popular mythology have tied UAP sightings to nuclear weapons tests, but no peer-reviewed studies have tested this statistical link. In their paper published in the journal Scientific Reports, the VASCO team found a statistically significant association between transient occurrences, nuclear weapons testing and UAP reports.
To reach this conclusion, the researchers compiled a dataset spanning 2,718 days to compare the dates for transient sightings with the dates of above-ground nuclear tests and the number of UAP reports.
They found that transients were 45% more likely to be observed within one day of a nuclear weapons test. And the number of these flashes increased significantly when UAPs were spotted. Specifically, the total amount of transient activity increased by 8.5% for every additional UAP sighting. The study also found that UAPs were slightly more common during nuclear testing windows.
“Our findings provide additional empirical support for the validity of the UAP phenomenon and its potential connection to nuclear weapons activity, contributing data beyond eyewitness reports,” commented the researchers in their paper.
Edging closer to solving the mystery
The scientists do not claim to know the exact cause of the transients or the nature of the UAPs. However, their work can help rule out some of the theories. For example, the correlation with nuclear tests suggests the flashes are not plate defects, as it is highly unlikely these errors would cluster around specific historical dates.
Also, the fact that transients were likely to appear one day after nuclear tests suggests that they are not atmospheric debris from bombs, which would likely streak across the sky shortly after detonation. While the mystery of what these transients are remains unsolved, this study significantly narrows down the possibilities for future investigations.
Written for you by our author Paul Arnold, edited by Gaby Clark, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive.
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More information:
Stephen Bruehl et al, Transients in the Palomar Observatory Sky Survey (POSS-I) may be associated with nuclear testing and reports of unidentified anomalous phenomena, Scientific Reports (2025). DOI: 10.1038/s41598-025-21620-3
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Mysterious transient objects in sky linked to nuclear testing and unidentified anomalous phenomena (2025, October 27)
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