October 2025
Researchers studying thousands of digitized astronomical images from the pre-satellite era have found likely evidence of Unidentified Anomalous Phenomena (UAP), previously called UFOs, appearing in the sky at the same time as nuclear weapons tests.
PHOTO Astrovariable / Pixabay
The peer-reviewed research, which was published in October in two studies in Scientific Reports and Publications of the Astronomical Society of the Pacific, gives a new level of scientific credence to UAPs.
The group of international researchers — led by Beatriz Villarroel of Nordita, and KTH Royal Institute of Technology at Stockholm University — found that anomalous flashes of light in the sky recorded at CalTech’s Mount Palomar Observatory from 1949 to 1957 were likely caused by sunlight reflecting momentarily off very flat, highly reflective objects in high earth orbit. Those flashes coincided statistically with the timing of nuclear tests and eye-witness UAP sightings.
The research team examined other explanations for the correlations, but found them either highly unlikely or impossible.
“You don’t get that kind of solar reflections from round objects like asteroids or dust grains in space, which leave streaks during a 50-minute exposure,” says Villarroel. Satellites were ruled out, too, because the images pre-date the space age and satellite launches. The sky was pristine compared to today.
The new studies also show at least some of these single flashes, called “transients” by astronomers, were real objects, not defects on the plates or image “noise.” The research also investigated, and dismissed, hypotheses that the flashes were an unrecognised atmospheric effect of nuclear testing, or the result of damage to Palomar photographic plates due to nuclear fallout.
The United States, the Soviet Union, and Great Britain conducted at least 124 above-ground nuclear tests during the time period of the Palomar photographs.
The groundbreaking study made another remarkable finding: UAP sightings by pilots, military personnel and other eye-witnesses became more common after nuclear weapons tests. This statistical association has not previously been reported in peer-reviewed literature.
The connection between the timing of the distinctive yet unexplained flashes recorded by the observatory telescope camera, eye-witness reports of UAPs, and nuclear tests, is statistically significant, wrote the researchers, who analysed the massive data set (106,000 photographic plates from Palomar).
The flashes were 68 percent more likely to occur the day after a nuclear weapons test than on days without. In addition, the number of flashes increased by an average of 8.5 percent for each report of UAP. When both these reports and nuclear tests coincided, the effects were additive, with more than twice as many flashes of light as on days without either nuclear tests or reports.
“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,” concluded the paper in Scientific Reports.
Some of the most dramatic flashes were recorded on July 19, 1952, at 8:52 (UT), when Palomar documented three transients in a straight line, each as bright as stars on photographic plates.
Fascinatingly, those images coincided with an episode of major UFO sightings in the Washington, D.C., area.
An official record from the National Archives of Australia reveals that while the average monthly number of UFO reports of sightings between 1948 and 1951 was 15 per month, there were approximately 536 reports in July 1952.
The studies are part of a larger effort called the Vanishing & Appearing Sources during a Century of Observations (VASCO) project. It searches large data sources for vanishing objects and other anomalies in the sky by comparing historical sky surveys with modern data. The goal is to find unusual astrophysical phenomena and also identify the most interesting candidates in the interdisciplinary effort SETI, Search for Extra-terrestrial Intelligence.
Written by Tom Zolper
Edited by Liza Horan
