Unexpected patterns in historical astronomical observations

Researchers at Nordita, Stockholm University, together with international colleagues at Vanderbilt University, have published two new studies that show that historical astronomical observations contain unexpected patterns. The results are based on short-lived flashes of light captured on photographic plates from the early 1950s within the VASCO project (Vanishing & Appearing Sources during a Century of Observations). The project analyzes digitized astronomical plates to identify sources that blink, disappear or suddenly appear – and in this way better understand both natural and previously unexplained phenomena.

“Today we know that short flashes of light are often solar reflections from flat, highly reflective objects in orbit around the Earth, such as satellites and space debris. But the photographic plates analyzed in VASCO were taken before humans had satellites in space,” says Beatriz Villarroel, a researcher at Nordita at Stockholm University. 

The first article, published in Scientific Reports (Nature Portfolio), analyzes over 106,000 flashes of light, or transients, that look like stars appearing and disappearing within a single exposure. The study shows statistical connections between the phenomena, reports of UAP, and atmospheric nuclear weapons tests during the 1950s. 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 increases 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.

“The magnitude of the association between these flashes of light and nuclear tests was surprising, as was the very specific time at which they most often occurred—namely, the day after a test. What they might represent is a very fascinating question that needs further investigation,” says Stephen Bruehl of Vanderbilt University.

The second paper, published in Publications of the Astronomical Society of the Pacific (PASP), specifically looks for signs of possible extraterrestrial artifacts in orbit around Earth, before the first human satellite launch in 1957. The researchers looked, among other things, for instances where multiple flashes of light were along a line or in a narrow band—something that indicates reflections from flat, reflective objects in motion. Two interesting examples were identified, one of which occurred on July 27, 1952, the same night as the notable sightings of UAP in Washington, D.C.

The same article tests a method that the research team recently published in the Monthly Notices of the Royal Astronomical Society (MNRAS): comparing how often the phenomena occur in the Earth's shadow, where solar reflections cannot occur. The new article in PASP, which again studies more than 106,000 transients seen across the northern starry sky, shows a clear deficit of flashes of light in the Earth's shadow, with one-third missing, suggesting that at least one-third of the phenomena were caused by solar reflections from highly reflective objects in high orbits.

For a long time, single points of light on astronomical plates have been dismissed as defects, even when they looked like real stars. The new studies show that some of these phenomena are actually real objects and exhibit patterns that cannot be explained by chance or image noise.

“Amidst what has been perceived as noise on the plates, there seems to be a genuine population of phenomena that correlate with, among other things, nuclear weapons tests or reports of UAP and that are missing in the Earth's shadow. 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, but only if something is very flat and very reflective and reflects the sunlight with a short flash,” says Beatriz Villarroel.
The results are unexpected and indicate that some of the small dots on the plates may be due to reflections from physical objects in high orbit around the Earth.

The study in Scientific Raports: https://www.nature.com/articles/s41598-025-21620-3
The study in Publications of the Astronomical Society of the Pacific: https://iopscience.iop.org/article/10.1088/1538-3873/ae0afe
 

Last updated: October 20, 2025

Source: The Communications Office