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Beatriz Villarroel

An icebreaker

An astronomer at Sweden's Nordita compares historical sky photographs to modern surveys, hunting for stars that appear to have vanished. Her 2025 paper linking these transients to nuclear tests, published in a peer-reviewed journal, has drawn a published rebuttal disputing the correlation.

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Worth knowing · 1 of 5
What is the VASCO project, and who leads it?
VASCO, short for 'Vanishing and Appearing Sources during a Century of Observations,' compares old photographic sky surveys against modern digital ones, searching for objects present in one and missing from the other. It's led by an astronomer at Nordita in Stockholm.
Worth knowing · 2 of 5
What did the first VASCO paper, in 2019, find?
Published in The Astronomical Journal, it reported about a hundred catalogued point sources that could not be found in modern surveys, and follow-up observations of one of them that ruled out neither a flaw nor a real change.
Worth knowing · 3 of 5
What does the 2025 nuclear-testing paper claim?
Published in Scientific Reports, it reported that brief transient flashes on 1950s sky-survey plates were statistically more likely to appear within a day of a nuclear test, and weakly correlated with modern UAP reports on the same dates.
Worth knowing · 4 of 5
Has that claim been challenged?
Yes. A 2026 peer-reviewed paper argued the correlation is fully explained by the Palomar telescope's own observing schedule during that period, not by any connection to nuclear tests. Her team has answered in a preprint.
Worth knowing · 5 of 5
Are these transients claimed to be extraterrestrial technology?
Not as a firm claim — an unexplained natural process has been called exciting enough on its own, with extraterrestrial technology treated as one distant, unproven possibility among several, and disagreements meant to be settled through published papers rather than public argument.
Words to know
VASCOVanishing and Appearing Sources during a Century of Observations — a project comparing historical and modern sky surveys.
TransientA brief, unexplained flash or point of light on a photographic plate, present in one exposure and absent from others.
TechnosignatureA signal or trace proposed as possible evidence of technology built by a non-human civilization.
More words
POSS-IThe First Palomar Observatory Sky Survey, made in the 1950s, whose plates are central to this research.
A voice · 1 of 3
Beatriz Villarroel · Astronomer who leads the VASCO project

Since founding the project, she has compared historical and modern sky surveys for objects that appear to vanish, publishing a 2019 case in The Astronomical Journal and a 2025 nuclear-test correlation in Scientific Reports, while stressing that any explanation, mundane or not, would be scientifically significant.

A voice · 2 of 3
Wesley Watters · Astronomer who published a critical review

Leading a 2026 evaluation published in the Publications of the Astronomical Society of Australia, he argued that the correlation between transients and nuclear tests is fully accounted for by the Palomar telescope's own observing schedule, not by any real physical link.

A voice · 3 of 3
Nigel Hambly · Astronomer who has reviewed the plate data

Analyzing the same kind of archival plates in his own work, he has said that apparently real things in old data have often turned out to be flaws, and recommended examining the original plates directly to separate what's real from what's spurious.

A line to leave them with
The plates are real and archived. What made the marks on them is not yet settled.
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