Transients in the Palomar Observatory Sky Survey

[Mick West]

Thanks, everyone, for keeping the discussion largely polite and professional in recent posts. I know it's tempting to wander off into a discussion of motives or more aggressive criticism in a long thread like this. At times, the thread has drifted over the line of the politeness policy.

The PP is there to remove distractions for both casual readers and those directly addressed by the topic. I would appreciate it if people could refrain from snark, jokes, motive speculation, and anything that might be perceived as impolite in public discussions, especially the more technical ones.

 

[John J.]

My personally favored explanation would be some undocumented upper-atmosphere explosion experiment, or perhaps some high-altitude artificial platform producing short flashes.

I guess this can't be ruled out, but I think it's unlikely re. fixed-wing platforms for reasons given in post #794.
A large majority of the POSS-1 plates were developed before possible candidate high-flying aircraft (realistically only U-2, RB-57D) were in service.
Villarroel et al. don't report a much higher incidence of claimed transients in later plates AFAIK.
If aircraft flying at more common altitudes could cause pseudo-transients, it would be a well-understood issue amongst astronomers and Villarroel's findings would be readily explained.

Considering the shape of most balloon envelopes, maybe it's unlikely reflected sunlight would cause a brief flash (and through some of the night even high altitude balloons would be beyond the reach of sunlight). A large program of balloons carrying bright, intermittently used lights over 9 years, coinciding with POSS 1, flying within sight of the Palomar Observatory doesn't seem very likely.

No satellites or spacecraft before 4th October 1957, and very few for some years after (part of the attraction of POSS 1's timeframe for Villarroel et al.). The large number of reported transients across much of the sky probably rules out sub-orbital rockets/ missile tests, and we'd probably be aware of an extensive program using (e.g.) exploding or light-carrying sounding rockets/ high altitude military missiles by now.

 

[yoshy]

They have a new web page https://ghostsintheglass.com/, though.

Is the website gone? I'm getting a 404 error. I previously commented I found the website strange, as I have rarely ever seen a researcher use AI to make a website for themselves like that. Here's the archived version: https://web.archive.org/web/20250809083941/https://ghostsintheglass.com/

 

[jdog]

Is the website gone? I'm getting a 404 error. I previously commented I found the website strange, as I have rarely ever seen a researcher use AI to make a website for themselves like that. Here's the archived version: https://web.archive.org/web/20250809083941/https://ghostsintheglass.com/

Entirely possible the site had nothing to do with the authors and was set up by a third party having an LLM digest the paper and a few relevant links and spit out the HTML for a website. There's no ownership listed.

The domain was set up on August 7, 2025; I would guess whoever produced the site only paid for a year's worth of hosting and just let it expire.

Here's the WHOIS lookup information:
https://ghostsintheglass.com/
Name GHOSTSINTHEGLASS.COM
Registry Domain ID3007860146_DOMAIN_COM-VRSN
Registered On 2025-08-07 T04:22:49Z
Expires On 2027-08-07 T04:22:49Z
Updated On 2026-07-15 T13:37:40Z

privacy details redacted, but contact information was at:
Mailing Address: Kalkofnsvegur 2, Reykjavik, Capital Region, 101

A location which turns out to be "A Reykjavik building that houses a penis museum and an H&M is also the virtual home to an array of perpetrators of identity theft, ransomware and disinformation." https://www.nytimes.com/2024/10/09/business/iceland-online-disinformation-identity-theft.html

 

[yoshy]

A location which turns out to be "A Reykjavik building that houses a penis museum and an H&M is also the virtual home to an array of perpetrators of identity theft, ransomware and disinformation." https://www.nytimes.com/2024/10/09/business/iceland-online-disinformation-identity-theft.html

Thank you. I should've known this was the work of the penis museum and H&M in cahoots!

 

[Fritzkquzerk]

Entirely possible the site had nothing to do with the authors and was set up by a third party having an LLM digest the paper and a few relevant links and spit out the HTML for a website. There's no ownership listed.

The domain was set up on August 7, 2025; I would guess whoever produced the site only paid for a year's worth of hosting and just let it expire.

Here's the WHOIS lookup information:
https://ghostsintheglass.com/
Name GHOSTSINTHEGLASS.COM
Registry Domain ID3007860146_DOMAIN_COM-VRSN
Registered On 2025-08-07 T04:22:49Z
Expires On 2027-08-07 T04:22:49Z
Updated On 2026-07-15 T13:37:40Z

privacy details redacted, but contact information was at:
Mailing Address: Kalkofnsvegur 2, Reykjavik, Capital Region, 101

A location which turns out to be "A Reykjavik building that houses a penis museum and an H&M is also the virtual home to an array of perpetrators of identity theft, ransomware and disinformation." https://www.nytimes.com/2024/10/09/business/iceland-online-disinformation-identity-theft.html

Did I read correctly?

 

[John J.]

Did I read correctly?

Yes, they have H&M in Iceland! 64.148195, -21.935268, Google Maps shows a couple of others in Rekyjavik.

It shares a building with the Icelandic Phallological Museum, Wikipedia https://en.wikipedia.org/wiki/Icelandic_Phallological_Museum
I didn't know the Icelanders were into hot curries, but I guess in that climate a good phall is appreciated once in a while.

 

[JMartJr]

I didn't know the Icelanders were into hot curries

My limited experience with traditional Icelandic cuisine would make it very plausible that most any foreign cuisine would be popular there.

 

[Fritzkquzerk]

My limited experience with traditional Icelandic cuisine would make it very plausible that most any foreign cuisine would be popular there.

I never thought we would be talking about this on a thread about Transients!

 

[Todd Feinman]

I never thought we would be talking about this on a thread about Transients!

Most of the transients around here couldn't afford Icelandic cuisine; it's hard just to get by these days, for many.

 

[Smythe Bacchus]

I realise the prepublication release of the Watters et. al. critique of the 2025 VASCO research papers has already been cited on Metabunk. This article provides an update and brings it all together.

Article:

A study claimed UFOs orbited Earth in the 1950s. Then scientists checked the math.

By Adam Frank, Big Think, August 27, 2026

In October 2025, a group of researchers published a paper in a well-regarded, peer-reviewed astronomical journal claiming the extraordinary: They'd found evidence of objects orbiting the Earth years before the launch of any human-made artificial satellites. In another paper, they also claimed links between when these objects appeared in the sky and the dates of nuclear tests in the 1950s. If any of these results were correct, it'd represent evidence of orbiting non-human technological artifacts and an indication that whatever "piloted" these artifacts was interested in our nuclear capabilities. It's easy to see why the papers grabbed headlines and interest.
...
So, of course, these papers made news. A scientific paper on its own, however, is just a single step in the scientific process. The next step is for the community to pore over the paper and see if the work holds up. Was the data set well prepared? Are the methods used to analyze that data well thought out and mathematically legitimate? Are the conclusions the authors draw from their analysis appropriate, or is there some flaw in the chain of reasoning?

A critique of the VASCO studies
That next step just came in with a new paper called "Critical Evaluation of Studies Alleging Evidence for Technosignatures in the POSS1 – E Photographic Plates," which was recently accepted by the Publications of the Astronomical Society of Australia (PASA). As the title implies, the authors do not find the VASCO studies convincing.

Before we dive into their critique, one noteworthy thing about the paper is its author list. It includes several working scientists who have been at the forefront of taking UAPs seriously. The lead author is Wesley Watters of Wellesley College. He is an astronomer who has written several papers reviewing UAP sightings and arguing they deserve a deeper, agnostic analysis. He has also been a member of Avi Loeb's Galileo Project research team, which wants to study UAPs scientifically. Another author is Kevin Knuth, a physicist at the University at Albany, SUNY. Knuth published a well-known study of Navy-pilot UAP sightings exploring whether the trajectories seen by the pilots showed evidence for extreme physics at work. Knuth is also a research affiliate of the Galileo Project. What is striking about the author list is that it represents a group that cannot be seen as hostile to the basic idea that UAPs are a valid scientific problem or that they might represent technosignatures. This observation tells you nothing about the quality of their analysis and the critique that follows. It does, however, mean this is not a group of scientists with a bias against UAPs as a whole (in my experience, most astronomers do have this bias).

The Watters paper begins with an important historical example. Using photographic plates to look for things in the sky that appear and then disappear is not a new idea. For decades, astronomers tried to use photographic plates to find optical traces of the enigmatic gamma-ray bursts (GRBs), powerful explosions involving massive stars. As Watters and team show, even though a huge effort was put into the project, there were just too many "defects" on the plates that had nothing to do with the sky: problems with the photographic emulsion; dust grains on the plates; pits in the glass plate itself; errors introduced when plate copies were made, as well as other issues. It turns out that separating the defects and other issues from the real things captured by the telescope is incredibly difficult. This is especially true when you need to do it at scale — meaning you want to do statistics with tens or hundreds of thousands of potential transients. For the astronomers looking for GRBs, the photographic plates were simply not up to the job. That seems to be an important lesson for the VASCO project.
...
How did their choices of what to use effect their analysis and their claims?

It turns out that these are not easy questions to answer because the VASCO team did not publish the dataset used in this study. That means Watters and company had to go through an exhaustive effort to determine which parts of the POSS-I survey were used and which features were selected to be explored by the VASCO group as possible transients. Once this work is done, Watters and company go on to show that this analogous dataset is full of irregularities (something also shown in an earlier paper by Nigel Hambly of the University of Edinburgh).
...
Finally, the Watters paper concludes by showing how the whole VASCO project is plagued by a kind of circular reasoning embodied by their overuse of the term "transients" rather than "features." Circular reasoning involves assuming the conclusion of an argument as part of its premises. The VASCO team wants to claim that some features on the POSS-I plates are actual things in the sky that only appear once and then are gone. They use the analysis of the shadow deficit and nuclear tests to claim these are real transients. But there is no independent validation that the bulk of these "transients" are not stuff screwed up on the plates themselves. Thus, the argument doubles back on itself: the shadow-deficit analysis assumes that the plate features are real transient events, and that same analysis is cited as proof that they are real transient events.
...
Science and UFO culture
The first thing to note is that this is not the end of the story. Science is like the blues — it's a call-and-response kind of thing. A scientist named Bob publishes a paper. Another scientist named Alice publishes a critique. It's then Bob's job to address those critiques in the next published paper. If that's done well, then the game goes on, and Bob's evidence and arguments get better over time until, perhaps, the scientific community recognizes it as a proven fact and even uses that fact to do the next set of studies. So, the question now is how the VASCO team responds to these criticisms.
...
This takes us deeper into the difficulty for scientists attempting to deal seriously with UFO culture. Advocates for the claim that UAPs/UFOs represent technosignatures of alien visitation often complain that scientists ignore the evidence and are unwilling to take the subject seriously. This was certainly not the case with the VASCO papers. Dr. Villarroel was, for example, invited to present her results at a meeting of the important Goddard Space Flight Center technosignature lecture series. The meeting was polite, with lots of good discussion.

When, however, scientists find fault with UAP/UFO data — as is the case with the Watters study — they are attacked as "part of the problem" or "government shills." Online and elsewhere, it can get so unpleasant that at some point, a scientist might ask, "Why bother?" Everyone has interesting, fun research projects. Why spend time on this?

In this way, the UAP/UFO community needs to ask itself a difficult question. Does that community want their subject to be part of the actual scientific process — where beliefs can get legitimately challenged — or do they just want to hold on to their beliefs no matter what? There is a word for the second option. It's called religion.

Source: https://bigthink.com/13-8/a-study-claimed-ufos-visited-earth-in-the-1950s-then-scientists-checked-the-math/

Research is an iterative process. How a researcher reviews and responds to critique is just as important as the research itself. Credibility is not about always being right. It is about inviting scrutiny by releasing your data and analysis for independent review. It is being ready to have your methods and conclusions challenged, and being ready to acknowledge when you've made a mistake, and learn from it.

I want to see VASCO improve their work.

 

[FatPhil]

Article:

That next step just came in with a new paper called "Critical Evaluation of Studies Alleging Evidence for Technosignatures in the POSS1 – E Photographic Plates," which was recently accepted by the Publications of the Astronomical Society of Australia (PASA). As the title implies, the authors do not find the VASCO studies convincing.

Source: https://bigthink.com/13-8/a-study-claimed-ufos-visited-earth-in-the-1950s-then-scientists-checked-the-math/

No, that's not what "critical" necessarily implies in the field of academia. Common words can have subtly different meanings from their normal use. For example, most well known, "theories" quite often aren't just theories, and Hardy wasn't sorry about anything when he wrote /A Mathematician's Apology/ (OK, that's a bit more of an esoteric one, see https://en.wikipedia.org/wiki/Apology_(Plato) ). "Critical" just means that a careful and reasoned judicious evaluation is being made - it may even come out in support of the work. (Such alternative interpretations of the word shouldn't be a surprise, I would hope that most people are familiar with popstars having critical success, and with critical race theory being taught, etc.)

 

[JMartJr]

As "skeptical" in our context would not mean thinking every claim is false, .but instead that we'd like to see the evidence and where it leads...

 

[HoaxEye]

"Paper-parity" run has completed. Report and data: https://github.com/jannefi/poss1-pl...esults/s0-642-paper-parity-20260828/README.md

This release does not replace or change anything I released previously. It's a separate release that can be used to see the differences between my parameters and the ones described in MNRAS 2022. Veto catalogues used: Gaia and PS1. Spike mask: USNO-B. No other pipeline changes except a bug fix in deduplication phase - which turned out to be a real issue, potentially affecting all previous releases. All this is described in the linked README document.

Rows after pipeline: 134,976 (9,9% increase compared to previous one). 81,7% of S0 rows are common. Rows after selected post-process steps: SuperCOSMOS, PTF and EDGE: 81,409.

Agreement rate with MNRAS 2022/PASP 2025 datasets is very good also in this version.

This run confirmed what I saw in the previous one: my S0 contains a lot of excess detections, which are probably plate emulsion or scan defects in POSS-I red scans. For some reason, this affects only 244 of 642 plates. I call them "hot plates". The same can be observed in my previous run with different parameters.

I did some analysis, see: https://github.com/jannefi/poss1-plate-slice/blob/main/docs/HOT_TILE_BLUE_PLATE_CHECK.md I first checked and eliminated four possible explanations: 1) un-vetoed Gaia stars, 2) astrometrically displaced catalogued stars, 3) scan artifacts (they survive an independent SuperCOSMOS digitization of the same plates), and 4) USNO-B-catalogued sources. Now I have one hypothesis left and some supporting evidence, but I could not find a good solution. The excess data remains for now, and I don't know how to remove it systematically.

Note: code for this release can be found under "paper-parity" branch: https://github.com/jannefi/poss1-plate-slice/tree/paper-parity

 

[HoaxEye]

New preprint: Microscopy assessment of two multiple-transient candidates, Jun Yang & Beatriz Villarroel. Link: https://arxiv.org/abs/2608.26371 (submitted 26 Aug 2026). PDF version is attached.

Short summary: the paper physically re-examines two previously published "multiple transient" cases on POSS-I plates: the nine-source event of 12 Apr 1950 (XE325, Villarroel et al. 2021) and the triple-source event of 19 Jul 1952 (XE186, Solano et al. 2024). They inspected the original Caltech glass plate (XE325) and a Harvard copy plate (XE186) under a 25× magnifier + camera, and registered those images against the published digitizations.

Paper's result: all candidates are confirmed present on the physical emulsion at the catalogued positions (not a scanning/digitization artifact), and appear slightly sharper/rounder than ordinary star images - qualitatively consistent with a sub-second flash during the ~50 min exposure.

But the paper is explicit that this doesn't settle anything: magnified inspection alone cannot distinguish a genuine flash from an ordinary emulsion defect at the level of a single source. Both look the same under a loupe. The one test that would actually be decisive, a simultaneous second-site plate for a parallax check, isn't available for either event. No discovery claim is made: the authors call for population-level statistics and future multi-station imaging instead.

 

[Ann K]

In this way, the UAP/UFO community needs to ask itself a difficult question. Does that community want their subject to be part of the actual scientific process — where beliefs can get legitimately challenged — or do they just want to hold on to their beliefs no matter what? There is a word for the second option. It's called religion.

https://bigthink.com/13-8/a-study-c...n-the-1950s-then-scientists-checked-the-math/

This needs to be said often and loudly. Scientists learn very early in their careers to expect that not everyone will agree with their conclusions. To get one's feelings hurt may be understandable, but to whine publicly about it just opens the criticism to a wider audience.

 

[yoshy]

I realise the prepublication release of the Watters et. al. critique of the 2025 VASCO research papers has already been cited on Metabunk. This article provides an update and brings it all together.

Article:

A study claimed UFOs orbited Earth in the 1950s. Then scientists checked the math.

By Adam Frank, Big Think, August 27, 2026

Source: https://bigthink.com/13-8/a-study-claimed-ufos-visited-earth-in-the-1950s-then-scientists-checked-the-math/

I don't see anything in this article that can qualify as personal attacks or anything like that. Will Villarroel et al respond to these critiques? Or ignore them on the basis of personal attacks and/or misogyny?

 

[NorCal Dave]

I don't see anything in this article that can qualify as personal attacks or anything like that. Will Villarroel et al respond to these critiques? Or ignore them on the basis of personal attacks and/or misogyny?

Reply is here maybe?:

https://arxiv.org/abs/2602.15171

We respond to the critique by Watters et al. (2026) of the statistical analyses in Villarroel et al. (2025) and Bruehl & Villarroel (2025). We argue that the critique conflates object-level validation with ensemble-level statistical inference and relies on a reduced, heterogeneously filtered subset originally constructed for a different scientific purpose. We further question whether the aggressively filtered subset used in Watters et al. (2026) demonstrates a meaningful improvement in sample purity, given the twenty-fold reduction in sample size. Our simple, visual check does not suggest that it does. The subset further lacks complete temporal information and is seriously statistically underpowered for testing the reported Earth-shadow deficit. We emphasise that the horizontal separation metric used for plate assignment and time reconstruction as in Watters et al. (2026) depends on the inclusion of the cos(Dec) factor to ensure geometric consistency. Any omission would alter plate assignment and inferred observation times. Moreover, the analyses presented in Watters et al. (2026) do not include uncertainty estimates or error propagation, limiting the interpretability of the claimed null results. We conclude that the principal findings reported in Villarroel et al. (2025) and Bruehl & Villarroel (2025) are not invalidated by the analyses presented in Watters et al. (2026).

 

[John J.]

Quote below from "A study claimed UFOs orbited Earth in the 1950s. Then scientists checked the math", Adam Frank, Big Think, August 27, 2026 as per @Smythe Bacchus' post #851. Frank's article discusses "Critical Evaluation of Studies Alleging Evidence for Technosignatures in the POSS1-E Photographic Plates", link provided by @sigmops in post #228, Digitized Sky Survey POSS-1 thread.

The lead author is Wesley Watters of Wellesley College. He is an astronomer who has written several papers reviewing UAP sightings and arguing they deserve a deeper, agnostic analysis. ...Another author ...Knuth published a well-known study of Navy-pilot UAP sightings exploring whether the trajectories seen by the pilots showed evidence for extreme physics at work. ...What is striking about the author list is that it represents a group that cannot be seen as hostile to the basic idea that UAPs are a valid scientific problem or that they might represent technosignatures.

If anything, Frank understates the evidence that some of the Critical Evaluation authors are open to the idea that UAP reports might indicate the presence of exotic artefacts.

Four of the five authors of "Critical Evaluation of Studies Alleging Evidence for Technosignatures in the POSS1-E Photographic Plates",
Wesley Andrés Watters, Laura Dominé, Sarah Little and Kevin H. Knuth were co-authors, along with Villarroel, of the paper (well, opinion piece)
"The New Science of Unidentified Aerospace-Undersea Phenomena" (link https://arxiv.org/pdf/2502.06794; thread New Science of UAP Paper).
Knuth was the lead author.

[This should have said "Four of the six authors", Cameron Pratt, Matthew Szenher are authors of "Critical Evaluation" but not "The New Science".]

The thread for "The New Science of Unidentified Aerospace-Undersea Phenomena" is well worth a read. Members here have noted the large number of listed authors, many of whom have well-documented beliefs that UAP reports represent sightings of exotic intelligently-controlled artefacts/ phenomena. There is discussion of the content of that paper. It contains no original research.
It discusses previous UFO/ UAP reports, but some are described/ summarized in ways that seem to be based on witness reports (or subsequent interpretations) that are not supported by other, possibly more reliable evidence about those events (e.g. Roswell, Malmstrom).
Some of the author's summaries arguably maximize the chances that a subject-naïve reader might believe that the cases being referred to are strong evidence of something extraordinary having happened, because the authors do not mention known evidence to the contrary, and sometimes repeat earlier claims that are highly questionable:

Roswell is mentioned under "Physical Evidence" but its probable cause is not. There was an "incursion" at Malmstrom air force base in 1967. The Ubatuba incident "involved the catastrophic explosion of a UFO". At Council Bluffs "about 11 people, in separate groups, witnessed an event where a hovering object dropped a large mass of molten metal"; but only 5 witnesses were identified; 2 claimed to see a hovering UFO, 3 others claimed to see something fall (but not from anything), none saw anything drop from a hovering object.

I think "Critical Evaluation of Studies Alleging Evidence for Technosignatures in the POSS1-E Photographic Plates" is of interest not just because of the content of that paper, but additionally because of the previous UAP claim-related work of some of its authors:
"Critical Evaluation" is wide-ranging and direct in its criticism of Villarroel et al.'s claims. Some of us (well, me anyway) might wonder why four of those authors chose to undertake this work when they have previously authored a paper, along with Villarroel and others, that is (I believe) uncritical, even accepting, of extraordinary claims which are largely anecdotal, some of which have been explained or shown to be highly questionable by further investigation. I guess moving to a more questioning position about UAP claims might be progress.

That 4 of its authors were also authors of "The New Science" doesn't have any bearing on the content of "Critical Evaluation", and that paper might be an important contribution to evaluating Villarroel et al.'s claims (although I think there were good reasons to be sceptical of those claims before "Critical Evaluation" and they have been discussed here).

Frank raises Watters' and Knuth's previous work related to UAP claims as evidence that they are not "hostile" to the idea that UAP reports represent technosignatures, i.e. they are evidence of (presumably exotic) technology. (Same applies to Laura Dominé, Sarah Little).
He (I think correctly) implies that it is therefore harder for members of the "UAP/UFO community" to dismiss the paper as the work of hostile authors.

But this might reflect a problem with that community, or at least some of its representatives. Just as "Critical Evaluation" should stand on its own merits, regardless of the prior work of its authors, so should any other paper (including those of Villarroel et al.) It shouldn't matter who the authors are (unless they have an established record of objectively flawed research or mistaken conclusions, in which case additional caution might be understandable).

People here are sceptical of Villarroel et al.'s work on transients not because of who she is, but because extraordinary claims have been made without (arguably) the transparency that might be expected to allow review/ replication of that work.
In the light of the extraordinary conclusions drawn by V. et al., it must have occurred to them that complete transparency would be expected.
The content of V. et al.'s papers, and the conclusions drawn from investigations that it is difficult for others to replicate, are the issue, not the authors.

Only accepting research which conforms to our prior beliefs, or from people we like (perhaps because their research conforms etc.), is to fundamentally misunderstand the scientific process. It does not help further our (or any individual's) understanding of objective reality; it is cherry-picking that reinforces beliefs that might be falsified by the research that is ignored.
I think Frank is right to ask

Does that community want their subject to be part of the actual scientific process — where beliefs can get legitimately challenged — or do they just want to hold on to their beliefs no matter what?

________________________________________________________________________________________________________________________________________________________

To be a bit pedantic, I'm not keen on Frank's phrasing in bold below,

...this is not a group of scientists with a bias against UAPs as a whole (in my experience, most astronomers do have this bias)

...I'm not sure most astronomers have a bias against UAP as a discrete, objective phenomenon to be studied; they just don't believe that the evidence indicates that there is a discrete, objective UAP phenomenon to be studied, and this might not be because they haven't considered the proposed evidence.
Not accepting a phenomenon exists because the claimed evidence for it isn't persuasive isn't a prejudice, and I'd suggest not a bias.
I don't expect many historians believe there is much to be gained by studying ghosts, although if they existed they might be a rich source of historical information. I wouldn't describe this as a bias, or an indication that Big History hasn't done enough to disclose what it knows about ghosts.
Many astronomers/ related scientists are at the forefront of investigating things in the sky, and almost all serious work around SETI comes from respected scientists within this field. If evidence for an extraterrestrial biosignature is found, it will almost certainly be discovered by "mainstream" scientists working as part of a larger collaboration.

 

[Fritzkquzerk]

Would it be possible to see if such defects or "transients" are much more common in general in this type of plates also from other observatories?
Because if we take this study alone, then It could really just come down to a series of different kinds of emulsion/photographic artifacts.
If these is a broader pattern It should be easily verifiable from other plates of the same period but from different areas?
No spec of dust or dot in a photo could ever count as evidence for Aliens or artificial objects, but it would be interesting to see.
It can easily disprove any claim about Alien ships if really these occurences were much more common than what claimed in their paper.

 

[Ann K]

I'm not sure most astronomers have a bias against UAP as a discrete, objective phenomenon to be studied; they just don't believe that the evidence indicates that there is a discrete, objective UAP phenomenon to be studied, and this might not be because they haven't considered the proposed evidence.
Not accepting a phenomenon exists because the claimed evidence for it isn't persuasive isn't a prejudice, and I'd suggest not a bias.

I think UFO/UAPs fall into the "extraordinary claims" category for which "extraordinary evidence" is required ...and the examination of old plates simply has not provided it. Nor has any other study done so to date, as far as I can tell.

 

[NoParty]

Sometimes an accusation of "bias!" means nothing more than that the accused
is aware that many, many fantastic claims, have yet to reveal any real, decent evidence.

 

[Mauro]

...this is not a group of scientists with a bias against UAPs as a whole (in my experience, most astronomers do have this bias)

...I'm not sure most astronomers have a bias against UAP as a discrete, objective phenomenon to be studied; they just don't believe that the evidence indicates that there is a discrete, objective UAP phenomenon to be studied, and this might not be because they haven't considered the proposed evidence.
Not accepting a phenomenon exists because the claimed evidence for it isn't persuasive isn't a prejudice, and I'd suggest not a bias.

Exactly!

In other words, 'bias' is just the amount of the prior, which is nothing else than the sum of all the past evidence. The prior against aliens visitors is so strong that being 'biased' (exactly by the amount of the prior) against that hypothesis is perfectly rational. Indeed, it's the only rational thing to do. In this sense, 'bias' is a good thing, while it becomes bad when it's much different from the prior, or even goes against it.

 

[yoshy]

Reply is here maybe?:

https://arxiv.org/abs/2602.15171

Thanks Dave! I did indeed miss that. The paragraph you copied isn't filling me with confidence that the critique is properly responded to, but I'll have to read it in full to have a fair judgement.

 

[NorCal Dave]

Thanks Dave! I did indeed miss that. The paragraph you copied isn't filling me with confidence that the critique is properly responded to, but I'll have to read it in full to have a fair judgement.

This appears to be their critique of Watters relevant to the nuke paper in the OP:

The next issue concerns the temporal correlations with nuclear weapon tests and UAP in Bruehl & Villarroel (2025). The critique by Watters et al. (2026) (Section 6) highlights the relatively small number of nights with Palomar observations, noting that the published article conservatively assumed zero transients on nights for which no transient was reported. The authors conclude that the apparent associations between transients and nuclear testing arise solely from coincidental overlap between nights of Palomar observation and nuclear testing schedules.

To address this concern, we downloaded the POSS-I observation dates and merged these with our analysed nuclear–transient dataset (observation dates from: https://vizier.cds.unistra.fr/viz-bin/VizieR (VI/25/nposs)). We then analysed the dataset restricted to the 370 nights with confirmed POSS-I observations.While at least one transient was observed on 72.8% of dates outside a nuclear testing window (±1 day), transients were observed on 84.2% of dates within a nuclear testing window. This ≈11% absolute difference is substantially larger than the 4.8% difference reported in the original paper.

The exact one-tailed -value (testing a directional hypothesis) for the dichotomous association between transients and nuclear testing is = 0.046. A non-parametric test likewise showed a significantly greater number of transients (Mann–Whitney, = 0.046) within a nuclear testing window compared to outside such a window. A Poisson generalised linear model analysis further revealed significantly more transients on POSS-I observing nights within, as opposed to outside, a nuclear testing window ( < 0.001).The reported correlation between the number of transients and the number of UAP sightings per night was essentially unchanged formour paper (Spearman = 0.13, = 0.011).

Finally, the analysis demonstrating that being within a nuclear testing window and having at least one UAP sighted on a given night produced additive effects on the number of observed transients remained highly significant( < 0.001), with the overall pattern unchanged. Thus, even when using the restrictive dataset suggested by Watters et al. (2026), the results reported in the Scientific Reports paper remain unchanged.

We further note that while coincidental timing between POSS-I observation nights and nuclear testing schedules might hypothetically contribute to associations between dichotomous occurrence of transients (presence/absence) and nuclear testing, it cannot account for findings that the actual number of transients is significantly higher when within a nuclear window. This issue is not addressed by the Watters et al. (2026) critique.

The results in Bruehl & Villarroel (2025) results have further been replicated by two professional data analysts.While not peer-reviewed,the results are consistent with our findings. See, for example, an independent analysis available online conducted by Janne Sinkkonen which controls for temporal clustering of observations.

Concluding the entire reply with a Higgs-boson comparison:

In summary, the 30-page critique by Watters et al. (2026) offers a detailed and systematic examination of the analyses presented in Villarroel et al. (2025) and Bruehl & Villarroel (2025). It makes acase for dismissing any sample with a large fraction of noise, but just as the Higgs boson could only be found by embracing the statistical power of a vast and noisy ensemble, we must not allow a hyper fixation on individual plate defects to obscure the clear, large-scale signals that remain imprinted on the historical sky.

While Watters et al. (2026) level of scrutiny can be valuable and motivates us for improving our methodology, the work by Watters et al. (2026) is undermined by a lack of careful alignment between the hypotheses being tested and the methodological frameworks and samples employed to test them. When combined with an inadequate treatment of uncertainties and statistical power, no accurate information on times and dates of the events, several of the resulting conclusions stem from misunderstandings. Taken together, the critique serves as a reminder that the present analysis establishes a robust starting point, not an endpoint. For now, the transients remain on the plate.

https://arxiv.org/pdf/2602.15171

 

[HoaxEye]

"Paper-parity" run has completed. Report and data: https://github.com/jannefi/poss1-pl...esults/s0-642-paper-parity-20260828/README.md

I did yet another analysis, this time about the differences of two full plate scans: IRSA (the ones I'm using) and STScI (the ones suggested by Villarroel). See: https://github.com/jannefi/poss1-plate-slice/blob/main/docs/SCAN_SOURCE_SENSITIVITY.md

The test was limited, but results are clear. STScI full plate scans feature pixel inversion at the plate edges. That will have impact on raw detection numbers as well as the final detections with this pipeline implementation.

If anyone wants to run my pipeline, it is better to use IRSA full plate scans. Otherwise there will be differences I can't fully explain. STScI scans will work as-is, and there will be no warnings or errors, just different results with plate edge data.

 

[yoshy]

In summary, the 30-page critique by Watters et al. (2026) offers a detailed and systematic examination of the analyses presented in Villarroel et al. (2025) and Bruehl & Villarroel (2025). It makes acase for dismissing any sample with a large fraction of noise, but just as the Higgs boson could only be found by embracing the statistical power of a vast and noisy ensemble, we must not allow a hyper fixation on individual plate defects to obscure the clear, large-scale signals that remain imprinted on the historical sky.

Mentioning the Higgs Boson feels like a false analogy fallacy (or perhaps there's a more accurate fallacy). It just feels like they are using the Higgs to lend credibility to their completely unrelated analysis. The response was 7 pages compared to 30 pages in the critique. It appears that much of the critique was just hand waved away and not actually addressed.

 

[John J.]

From Villarroel, Streblyanska, Bruehl and Geier's "A Response to paper Critical Evaluation of Studies...", https://arxiv.org/abs/2602.15171,
usefully quoted by @NorCal Dave, post #865, my emphasis:

Finally, the analysis demonstrating that being within a nuclear testing window and having at least one UAP sighted on a given night produced additive effects on the number of observed transients remained highly significant( < 0.001)...

I think this is interesting.

Villarroel et al. do not appear to suggest that the UFO sightings are sightings of their transients.
As far as I can tell the POSS1 transients have apparent magnitudes far below unaided human perception,
e.g. "A bright triple transient that vanished within 50 min", Solano, Villarroel et al. 2023, https://academic.oup.com/mnras/article/527/3/6312/7457759,

We report on three optically bright, ∼16th mag, point sources within 10 arcsec of each other that vanished within 1 h, based on two consecutive exposures at Palomar Observatory on 1952 July 19 (POSS I Red and Blue).

This is about as bright as Charon (Pluto's largest moon) as viewed from Earth- totally invisible to the naked eye (as is Pluto. As is much larger Neptune). In ideal conditions people with good vision might see magnitude 7 objects, Wikipedia https://en.wikipedia.org/wiki/Magnitude_(astronomy)

So (it is implied, I think) either the UFOs are "transients" popping down from orbit, or they're something else, another class of visiting extraterrestrial artefact.
This might be seen as circular reasoning: Transients being more more frequent at times of UFO reports might be evidence they're exotic tech.
The UFOs are of exotic origin because they're associated with the transients.
There is no persuasive testable evidence that UFOs (as exotic artefacts, or any other type of undescribed phenomenon) exist.
Villarroel et al.'s papers do not change this (as far as I can tell) unless we accept the reasoning above.
We know that many UFO reports are due to misidentifications. Some are hoaxes or tall stories.

There is no register of all claimed UFO/ UAP reports AFAIK (and realistically such a register might not be possible).
All sightings taken into account by Villarroel et al. are claimed sightings that happen to have been documented and recorded in whatever source(s) the authors used. They are unlikely to be fully comprehensive. [Edited to add, "No single source of UFO reports is likely to be fully comprehensive" might have been clearer.]

Hopefully Villarroel et al. used a specific, pre-selected source or sources listing UFO reports. If they retrospectively looked for UFO reports for specific days not using pre-selected sources (e.g. by googling), all sorts of confounding factors might arise: One might subconsciously try a little harder to find reports corresponding to the 3-day nuclear test windows or dates of plates identified as having a larger-than-average number of transients. Equally one might (subconsciously) not look for quite as long for reports not on those dates. Speculation; some UFO enthusiasts have been particularly interested in reports associated with nuclear sites, weapons tests etc.; repeated searches/ visits to webpages discussing such reports might make search engine algorithms push those webpages up the list, making them more visible (perhaps unlikely, I don't know).

(1) It would be interesting to know which list(s)/ dataset of UFO reports the researchers used (if any).
(2) It would also be good to know if Villarroel et al. "filtered" the claimed sightings: some of George Adamski's photos (e.g. the famous Venusian Scout Ship of 1952) are within the relevant timeframe and were widely publicized, but if his reported sightings are among those used by V. et al., there's a credibility issue. But if Adamski's December '52 encounter isn't included, it raises the question, what criteria were used?
Who decided, by what means, which reports were "real"?

There are other claimed sightings from the era that stretch credibility or which might be non-events sensationalised by local press (e.g. Farmington 1950). It is almost certain the majority of "genuine" sightings are misidentifications. None has ever been demonstrated to be of an exotic artefact or a novel phenomenon.

If claimed UFOs are actually misidentified balloons, jets etc. and/or hoaxed flying saucers, yet correlate with abundant transients and/ or nuclear tests in V. et al.'s studies (and I'm genuinely not ruling this out) it would be interesting, but of course it wouldn't support the author's implied hypothesis (that they are causally connected with transients which are themselves ET artefacts). It might suggest a flawed methodology in selecting claimed UFO reports that leads to something like type 1 error.
The authors cannot demonstrate that "their" UFOs are not misidentifications with a peppering of hoaxes.

NICAP has a webpage linking to "UFO Chronologies" for various years including the years of POSS 1, https://www.nicap.org/chronos/
To get some idea of the number of sightings NICAP recorded, I had a quick look at 1950 and 1956.
The 1950 UFO chronology, https://www.nicap.org/chronos/1950fullrep.htm. lists approx. 149 different sightings on approx. 113 days that year.
A large majority were from the USA. The 1956 chronology, https://www.nicap.org/chronos/1956fullrep.htm, lists approx. 122 sightings on around 104 days (a fair number of dates are uncertain) from a considerably wider range of places than 1950.
Whoever compiled these lists probably relied primarily on contemporary (mainly US?) newspaper reports, or other sources that once did.

It might be likely that many more sightings were made/ claimed; maybe not all local newspapers were archived and later digitized for the ease of later researchers, and NICAP / its contributors might not have had the resources to monitor all media outlets or other potential leads.
The Wikipedia article "List of reported UFO sightings", https://en.wikipedia.org/wiki/List_of_reported_UFO_sightings#cite_note-9, quotes Martin S. Kottmeyer writing in Why Statues Weep: The Best of the "Skeptik"

During the United States' initial 1947 wave, over 800 sightings were reported in the news.

.
World Population Review website (https://worldpopulationreview.com/country-rankings/ufo-sightings-by-country)

Between 1947 and 1969, the United States reported more than 12,000 different UFO sightings around the country.

-That's an average of more than 545 per year (though no references are given and figures given top of page appear to be from UK press items).

However, it seems possible that UFO reports are made every every day of the year in the USA alone, and have been since maybe the late 1940s.
If this is the case, it is a problem for finding correlations between days when UFOs are reported and other events- UFOs are seen every day!
Villarroel et al. would either have to be using a data set of UFO sightings that does not in fact list all known UFO sightings, or would have to use some means to select a subset of sightings which they believe are most relevant to their study.

I think it's possible that if someone looked hard enough (and had sufficient time and resources) they might be able to find a UFO report somewhere on the vast majority, if not all, of the days (nights) POSS-1 operated. This would have implications for claims that a higher number of transients correlates with days when a UFO is reported.

 

[jdog]

...
I think it's possible that if someone looked hard enough (and had sufficient time and resources) they might be able to find a UFO report somewhere on the vast majority, if not all, of the days (nights) POSS-1 operated. This would have implications for claims that a higher number of transients correlates with days when a UFO is reported.

There's another self-correlative effect in that -- the POSS-1 shots and UFO sightings roughly track with the weather. That is, you can't photograph the sky when it's cloudy; people don't see UFOs in the sky (or planets or bright stars) when it's cloudy.

The caveat being that Palomar, of course, is on a mountain in Southern California and Southern California conditions don't apply to the whole United States (though winter storms do move from west to east). And since people spend less time outdoors in the winter, they generally have fewer opportunities to see things in the sky and report them.