Transients in the Palomar Observatory Sky Survey

[Ann K]

If they place a lot of significance on three-point transits, do they ever attempt to explain why they aren't four-point, or five, or six? Is it merely a matter of the time of the exposure?

 

[FatPhil]

If they place a lot of significance on three-point transits, do they ever attempt to explain why they aren't four-point, or five, or six? Is it merely a matter of the time of the exposure?

Probablities of finding 2-way coincidences are much lower than single coincidences. (any two points define a line, it's finding the third point on the line that's a thing of interest.) If there was real signal - a real path something was following, it *wouldn't* be a "coincidence", and this reduction in probability wouldn't apply. If they're only finding 3s, and in quantity, but nothing longer, they're literally saying "these datapoints are most likely random noise".

I'm reminded of one of the "Torah Codes" claims and subsequent debunks from the 80s/90s (whereby debunkers find as many hidden messages in War and Peace or Moby Dick, remember those? Predictions of assasinations, etc.), specifically the "25 Trees" claim where almost all of the trees mystically hidden in the Genesis Garden of Eden story were 3 letter words. Yeah, things that short are going to be everywhere. (And it's harder in 1D space like text than it is in 2D space like, erm, space.)

 

[Ann K]

Yes, I was waiting for them to claim "two-point" lines...

 

[AmberRobot]

In a recent Scientific American article, Hambly said Villrroel and team should physically inspect the original plates for defects, which also implies that has not yet been done.

This is interesting because it seems that Villaroel has been doing this kind of research for about five years and keeps saying that they haven't looked at the original plates. A Google search (not sure how reliable this is) indicates that the original plates should exist, so it seems to me that not making an effort to examine them is a big red flag.

The most prosaic explanation is that Villarroel's transients are simply artifacts in the photographic plates such as speckles of dust, blobs in the emulsion or even radioactive particles. Nigel Hambly, an astronomer at the University of Edinburgh, who has previously analyzed Villarroel's work and who has extensive experience with photographic plates from Palomar and other observatories, says one way to check would be to study the original plates themselves rather than using digital copies. "I've been caught out many times by apparently real things turning up in my data," he says, especially when working with plates that weren't stored in pristine conditions. "When you actually physically examine the plates under a microscope, you begin to get a feeling for what's real and what's spurious," he says. "There's no shame in being wrong."

Source: https://www.scientificamerican.com/...-photograph-ufos-orbiting-earth-in-the-1950s/

 

[MapperGuy]

This is interesting because it seems that Villaroel has been doing this kind of research for about five years and keeps saying that they haven't looked at the original plates. A Google search (not sure how reliable this is) indicates that the original plates should exist, so it seems to me that not making an effort to examine them is a big red flag.

I would have to agree. Just out of curiosity I would have tried to examine at least one plate that had lots of transients on it. Excessive faith in your source material (the digitized photos) may become very embarassing, when later put to the test.

 

[jdog]

This is interesting because it seems that Villaroel has been doing this kind of research for about five years and keeps saying that they haven't looked at the original plates. A Google search (not sure how reliable this is) indicates that the original plates should exist, so it seems to me that not making an effort to examine them is a big red flag.

The plates are all apparently at Cornell University in New York: https://ecommons.cornell.edu/items/b85eec8d-3215-4999-b54b-f7c8e7aa5ace

Abstract
This guide provides a map from positions in the sky to the corresponding glass plate in the Palomar Sky Survey (POSS-1). To arrange access to the physical plates, please contact the Cornell University Library Rare and Manuscripts Collection at rareref@cornell.edu

Description
This document was produced by the Astronomy department at Cornell at some point between 1961 and 1965 to accompany the Palomar Sky Survey (POSS-1) glass plates. The materials were first housed in the Space Sciences Building and moved to the Physical Sciences Library. They now reside at the Rare and Manuscript Collections Division in Kroch Library.

 

[jdog]

Here's a fun New York Times article from 2007 about the historical travails of managing huge libraries of astronomical photographic plates -- especially after astronomy moved to using CCD sensors instead of film by the 1980s and no one cared about the old plates. And then trying to get the plates usably digitized rather than destroyed: https://www.nytimes.com/2007/07/10/...e_code=1.xk8.MMut.EfkWDNH8eMvj&smid=url-share

Since the early days of celestial photography, astronomers have had to allow for the fact that plates were made with a variety of emulsions and developed in different ways. Adding to the confusion, pictures of the same patch of sky were taken over the century with different telescopes under different atmospheric conditions and with different exposure times. In Dasch these judgments, once the province of the female computers, are made algorithmically with software developed by Mr. Mink and another researcher, Silas Laycock. When a plate is scanned, the brightness of its stars is compared against known values in an online catalog. The image is calibrated accordingly.

Almost as important as the plates are the metadata — detailed notes handwritten in logbooks and sometimes on the plates themselves. "Somebody's got to type it in," Mr. Simcoe said. "Nobody's got any software that can read cursive writing." As a first step, George Champine, a retired engineer with an interest in astrophysics, has taken 80,000 photographs of the pages, which are slowly being transcribed in India, with help possibly on the way from volunteers at the American Museum of Natural History.

 

[overlord]

I know when I originally used it, I did qualify it (bold by me):

But after March of 1956, and the possible changing of the problematic red emulsion, an additional 38 nuclear test resulted in 0 transients observed.

Yes, but that qualifier got lost along the way:

Knowing they stopped taking photos soon after this date, that's no surprise. @NorCal Dave already commented on March 1956 being likely the time when the survey switched to a better emulsion.

In this case, our normal is that transients are caused by defects in the photographic emulsion. This is established because they improved the emulsion, and saw less transients.

Which is also when a new emulsion was used for the red plates. When the red emulsion was updated in ~1956, the transients disappeared. I know, correlation is not causation.

I found this 1956 paper from the American Astronomical Society:

https://adsabs.harvard.edu/full/1956AJ.....61..399G

They do seem to note that the 103a, red emulsion was problematic, particularly closer to the edges of the plates (screen shots):

'103a' denotes an entire emulsion family, the quoted source considers '103a-O', which is blue sensitive not red, I did not read the rest of it.

My concern is about the unsupported (and in this case false) statement getting established as fact.

Source: https://medium.com/@izabelamelamed/not-seeing-the-star-cloud-for-the-stars-a010af28b7d6
- "Not Seeing the Star Cloud for the Stars" by Izabela Melamed (July 2025).

By 1956, 103a-E was replaced with improved emulsions, and glass copies remained in use until digital photography took over in 2000. Curiously, the vanishing stars finally vanished around the time 103a-E was phased out.

[...]

Despite the apparent error in the Medium article, it seems to be true that the "vanishing stars finally vanished" when Kodak 103-series emulsions were phased out. I've looked at POSS-II red plates and could not find any "glints" or "transients". My manual check was limited to handful of plates, though, but all POSS-I red plates are likely "peppered with such isolated detections" (see Hambly & Blair 2024, or the linked Medium post).

Google Scholar finds about 200 results for 'vanishing stars' and it's variants, a significant portion of that is poetry/literature related, suggesting that it's not common terminology in astronomy. Therefore I take "Curiously, the vanishing stars finally vanished around the time 103a-E was phased out." to refer directly to the works by Villarroel et al. As far as I know they only searched for transients in POSS I red plates.

"By 1956, 103a-E was replaced with improved emulsions, and glass copies remained in use until digital photography took over in 2000." - either refers to the general use of '103a-E', in which case it's not relevant based on the above, or it refers to the specific use by POSS I, in which case it is false.

Of course the notion that the 'transients disappeared' arises from Villarroel et al:

Article:

We also note an intriguing incidental finding regarding possible nuclear testing-transient links. The last date on which a transient was observed within a nuclear testing window in this dataset was March 17, 1956, despite there being an additional 38 above-ground nuclear tests in the subsequent 13 months of the study period.

Source: https://www.nature.com/articles/s41598-025-21620-3

Which is purely the result of their poor methodology, failing to consider the dates on which plates were recorded (this was mentioned a few times upthread), in the 1956-03-18 to 1957-04-28 period (406 days) there were a total of 5 days when plates were taken.

 

[Mendel]

. A Google search (not sure how reliable this is) indicates that the original plates should exist, so it seems to me that not making an effort to examine them is a big red flag.

They did consider it. From Solano 2022:

Article:

Clearly, a human inspection of the POSS I plates could solve the problem. However, the original plates of old sky surveys are treated like gold and accessing those plates is extraordinarily rare.

Source: https://academic.oup.com/mnras/article/515/1/1380/6607509?login=false

They did an excellent job removing artifacts anyway, back in 2022, reducing the set of transients to 5399. The new 2025 papers simply don't build on that work, and go back to a 100,000+ strong data set.

 

[Mendel]

My concern is about the unsupported (and in this case false) statement getting established as fact.

But is it?

@NorCal Dave found* a paper published in November 1956** that describes a better method to process the 103a-O photos; given publication timelines in pre-Internet days, I find it not at all unlikely that the process (if not the emulsion itself) had improved after March 1956, in the months when no photos were taken.

---

* https://www.metabunk.org/threads/transients-in-the-palomar-observatory-sky-survey.14362/post-355721
** https://adsabs.harvard.edu/full/1956AJ.....61..399G

 

[John J.]

I think a general concern of the group is that the paper's conclusions rely on a series of inferences based on a series of disputable (and often disputed) standards:

• Their definition of what counts as a glint and their dismissal of other researchers' interpretations of those spots as potential emulsion defects. The inference here is that these spots can't be from other causes and must be from reflective objects high in the atmosphere or in orbit.

"Their definition of what counts as a glint", i.e. identified by Villaroel et al. as a transient, might be very important.
At present, whether a feature on one photographic plate but not others is considered a "true" transient seems to be, to some degree, subjective- or at least, some astronomers with significant experience in astronomical photography disagree with Villaroel's criteria:
Hambly and Blair's 2024 paper states that some transients identified with high certainty by Villaroel et al. are likely to be emulsion flaws (and not necessarily from flaws on the original NGS-POSS-1 plates).

The absence of agreed objective criteria differentiating transients from photographic/ copying artefacts might open the door to misidentification of transients and subsequent type 1 error (e.g., and wholly hypothetically, there might be a slight- and unintentional- bias to classify features that support the hypothesis as transients; features that do not -perhaps appearing on non-nuclear test dates- perhaps get a second look, and are classified as flaws or other incidental inclusions).

The analysis should also incorporate the dates for when detonations were scheduled, but not conducted

Yes. Unless we credit the aliens with precognition, presumably they would go through their "get visible to monitor a test" routine a day before any scheduled test that did not in fact take place.

Maybe it's surprising Villaroel et al. didn't look for evidence of transients correlating with rocket testing (no orbital flights before 4th of October 1957- but it would have been evident, even using our current level of recce satellite technology, that the USSR and USA were developing that capability). UFO lore associates UFOs with rocketry/ spaceflight just as it does with nuclear tech, the inspiration for Villaroel looking for that correlation. That said, I guess we can't criticise a paper/ papers for not asking a different question.

 

[Mendel]

If they place a lot of significance on three-point transits, do they ever attempt to explain why they aren't four-point, or five, or six? Is it merely a matter of the time of the exposure?

There are, but they're picky about it.

https://iopscience.iop.org/article/10.1088/1538-3873/ae0afe#paspae0afes4

They found 20 4-point alignments, and 2 5-point alignments.
(Not knowing the shape of the transient distribution, I can't comment on how rare that is.)

However, their shortlist only has 1 of the 4-point alignments:

Why? "We show the most interesting candidates emerging after the visual inspection" translates to "these are the ones that looked good". Good means a low pmax value, which measures the width of the path bounding box.

The best 4-path has 5 arcsec width, presumably the others are worse. At geosynchronous orbit, that's 1 km wide. (Some "satellite"!)

So if we assume a single satellite that doesn't scare people when it passes before the moon, these 4-point and 5-point alignments don't really work.

 

[John J.]

The plates are all apparently at Cornell University in New York https://ecommons.cornell.edu/items/b85eec8d-3215-4999-b54b-f7c8e7aa5ace

I'm not sure that the linked-to Cornell University webpage, "Palomar Sky Survey 1 Plate Locator Guide", confirms that Cornell holds the original NGS POSS-1 plates (but I may well be mistaken).

The Caltech Archives website under "National Geographic Society - Palomar Observatory Sky Survey [NGS-POSS] Identifier: 2013-00051" says

Set of 1872 photographic prints from the original Palomar sky survey, conducted between 1949 and 1958 and funded by the National Geographic Society. These prints were the road atlas of astronomy for several decades. The original glass plates are stored at Palomar Observatory.

Hambly and Blair (2024) say

The originals are, we understand, archived in the Carnegie Observatories plate vault as part of the plate archive holdings of the Observatories of the Carnegie Institution for Science.

From the Palomar Observatory webpage they link to, under "Carnegie Observatories Plate Archive",

The Carnegie Observatories Plate Vault is home to the second largest collection of astronomical glass plates in the US. The plates (spanning the years 1892 – 1994) were created using telescopes at the Kenwood, Mt. Wilson, Palomar, and Las Campanas Observatories. Use their Plate Archives Search Tool (PAST) to search

"Plate Archives Search Tool" (PAST) is a clickable link to a Carnegie Institution for Science webpage "THE OBSERVATORIES Plate Archives", https://plates.obs.carnegiescience.edu/PAST/search/ (NB flagged up as "Not secure" on my browser), which has the Plate Archives Search Tool.
It confirms that plates from the Palomar 48-inch Schmidt (the Samuel Oschin telescope used for NGS POSS-1) are held, but it isn't immediately evident (to me) that that includes the POSS-1 plates (I'm sure some of you bright people here will be able to find out).

If the POSS-1 plates are held at the Carnegie Institution's Plate Vault, they are in Pasadena, California (Google Maps)

In the basement of the Observatories' Santa Barbara Street office is the plate vault, home to the second largest collection of astronomical glass plates in the United States. The plate collection consists of over 200,000 glass plate negatives, including spectra, direct object images, and solar plates. These glass plates date from between 1892 and 1994 were created using telescopes at the Kenwood, Mount Wilson, Palomar, and Las Campanas Observatories.

Carnegie Science webpage, "The Plate Archives" https://carnegiescience.edu/about/history/archives/plate-archives

 

[NorCal Dave]

103a' denotes an entire emulsion family, the quoted source considers '103a-O', which is blue sensitive not red, I did not read the rest of it.

You are right sir, I stand corrected. After reading through a number of papers I got the 103a-O and the 103a-E mixed up. At least one source I read, likely incorrect or only partially true, listed 103a as the red emulsion. From a 1991 paper about POSS II:

Eastman Kodak tyре-103а еmulsions were used for
both red and blue plates of the POSS I, with the blue
plates being unfiltered 103a-O and the red plates
combining 103a-E emulsion with a red plexiglass 2444
filter. The resultant spectral response functions (see
MA63) give effective wavelengths of~4100 A in the blue
(with a passband of~ 1100 A) and ~ 6500 Å in the red
(passband~500 A). The current survey is being taken in
three passbands: blue (IIIa-J emulsion and GG395 filter

Also from this paper it notes that the POSS I ended in late 1956:

With relatively short exposure times
(20 minutes in the blue, 40 minutes in the red), the plate
pairs were taken on the same night, with the first ac-
cepted plates being taken in July 1949 and the survey
completed in late 1956. Whiteoak further extended the
survey to a declination of-45° (or a zenith distance of 78°)
using red plates only.

https://adsabs.harvard.edu/full/1991PASP..103..661R

But it also notes that Whiteoak extended the survey with red plates only, but doesn't say for how long or if it was concurrent with the '49-'56 time frame, just at the -45 declination.

 

[AmberRobot]

They did consider it. From Solano 2022:

Article:

Clearly, a human inspection of the POSS I plates could solve the problem. However, the original plates of old sky surveys are treated like gold and accessing those plates is extraordinarily rare.

Source: https://academic.oup.com/mnras/article/515/1/1380/6607509?login=false

Sure, I understand that it may be difficult to get access to the plates, but because it is such a major potential test to their research program's critical hypothesis it comes across as a massive oversight to a reviewer like me. Did they report ever trying to get access and why they couldn't? In multiple of the papers, including Hambly's criticism of their work, the idea of looking at the original plates is mentioned, but there's been no mention of any attempt to get access.

And certainly i think I would want to check that out before I started considering alien spacecraft examining our nuclear explosions as the source.

 

[Gary C]

.... Unless we credit the aliens with precognition, presumably they would go through their "get visible to monitor a test" routine a day before any scheduled test that did not in fact take place.

Maybe it's surprising Villaroel et al. didn't look for evidence of transients correlating with rocket testing (no orbital flights before 4th of October 1957- but it would have been evident, even using our current level of recce satellite technology, that the USSR and USA were developing that capability). UFO lore associates UFOs with rocketry/ spaceflight just as it does with nuclear tech, the inspiration for Villaroel looking for that correlation. That said, I guess we can't criticise a paper/ papers for not asking a different question.

Continuing this line of reasoning, the visibility of the alleged NHI satellites should not change at all. In the early days of satellite reconnaissance/surveillance the systems used physical film that had to be ejected periodically, returning to Earth by parachute. These early spacecraft had to be maneuvered to low orbits over their targets during times of expected tests.

The following generations of spacecraft used increasingly advanced analog and later digital systems to reduce the need for special maneuvers to cover targets or events of interest. As the cost of launching and maintaining systems on-orbit has fallen, the major national intelligence services now operate a fleet of spacecraft that cover much of the globe and relay their data in real time through a dedicated satellite based communications network.

Our extant space-based surveillance systems don't have to do anything flashy in order to do their work. Villaroel et al. are describing behavior by NHIs during the 1950s that implies a less advanced technological base than 21st Century humans already posses.

 

[jdog]

I'm not sure that the linked-to Cornell University webpage, "Palomar Sky Survey 1 Plate Locator Guide", confirms that Cornell holds the original NGS POSS-1 plates (but I may well be mistaken).

The Caltech Archives website under "National Geographic Society - Palomar Observatory Sky Survey [NGS-POSS] Identifier: 2013-00051" says

Set of 1872 photographic prints from the original Palomar sky survey, conducted between 1949 and 1958 and funded by the National Geographic Society. These prints were the road atlas of astronomy for several decades. The original glass plates are stored at Palomar Observatory.

Hambly and Blair (2024) say

The originals are, we understand, archived in the Carnegie Observatories plate vault as part of the plate archive holdings of the Observatories of the Carnegie Institution for Science.

From the Palomar Observatory webpage they link to, under "Carnegie Observatories Plate Archive",

The Carnegie Observatories Plate Vault is home to the second largest collection of astronomical glass plates in the US. The plates (spanning the years 1892 – 1994) were created using telescopes at the Kenwood, Mt. Wilson, Palomar, and Las Campanas Observatories. Use their Plate Archives Search Tool (PAST) to search

"Plate Archives Search Tool" (PAST) is a clickable link to a Carnegie Institution for Science webpage "THE OBSERVATORIES Plate Archives", https://plates.obs.carnegiescience.edu/PAST/search/ (NB flagged up as "Not secure" on my browser), which has the Plate Archives Search Tool.
It confirms that plates from the Palomar 48-inch Schmidt (the Samuel Oschin telescope used for NGS POSS-1) are held, but it isn't immediately evident (to me) that that includes the POSS-1 plates (I'm sure some of you bright people here will be able to find out).

If the POSS-1 plates are held at the Carnegie Institution's Plate Vault, they are in Pasadena, California (Google Maps)

In the basement of the Observatories' Santa Barbara Street office is the plate vault, home to the second largest collection of astronomical glass plates in the United States. The plate collection consists of over 200,000 glass plate negatives, including spectra, direct object images, and solar plates. These glass plates date from between 1892 and 1994 were created using telescopes at the Kenwood, Mount Wilson, Palomar, and Las Campanas Observatories.

Carnegie Science webpage, "The Plate Archives" https://carnegiescience.edu/about/history/archives/plate-archives

Dizzy-head emoji!

The search tool for the Carnegie Science archive in Santa Barbara brings up only 353 results for 1947 to 1956 and they don't look like POSS-1 -- and POSS-1 should be more than 2,000 plates.

This 2008 blog post by the Cornell University Engineering Library says:

The Physical Sciences Library recently acquired the Palomar Observatory Sky Survey plates and prints, a complete photographic record of the night sky. During the 1950's, the National Geographic Society funded the project to produce celestial photographs using the Oschin Schmidt telescope at the newly-built Mount Palomar Observatory. In 1991, a photographic survey of the southern sky was begun, using three wavebands (blue, red and near infrared) to produce images and record the spectral type of objects in nearly 1000 celestial fields. The updated series, POSS II, was completed in June 2000.

The survey photos were produced in both paper and glass formats. The sets are fairly common, but the glass plates, which were sold to a number of research institutions including Cornell, contain better detail and less spatial distortion than the paper copies, and are therefore uniquely valuable to researchers.

So some libraries may have sets of original prints made from the plates, others may have the plates themselves.

Why the plates would be in New York rather than California is a good question.

 

[Mendel]

Our extant space-based surveillance systems don't have to do anything flashy in order to do their work. Villaroel et al. are describing behavior by NHIs during the 1950s that implies a less advanced technological base than 21st Century humans already posses.

It's worse than that, I think? The studies assume that most of the 100,000+ data points are objects in orbit (in a single hemisphere). For comparison, Starlink has under 10,000 nodes in orbit right now.

So the conclusion must be that the hypothetical aliens cover Earth in an absolute flood of satellites each time there's a test because while they know the date in advance, they have no clue which continent it'll even be on; and then pull all of these satellites, only to redeploy them for the next test weeks or months later.

 

[Eburacum]

Another possibility is that the 'Earth's shadow anomaly' is entirely consistent with the distribution of stars in the Milky Way.

My daughter, who is a mathematical biologist, has suggested that one way to test this would be to determine the stellar density for each plate using the real, accepted stars that appear in that location. This should allow us to see if the natural distribution of stars is so skewed that it explains the 'Earth Shadow effect' without recourse to alien GEO satellites.

 

[John J.]

Just thinking, during a lunar eclipse, the Moon is still visible due to reflected light from the Earth because of refracted light in the atmosphere.
I appreciate that the transients are of very low magnitude, but might we expect some of the brighter transients to still be imaged?-
-though I guess they might all be brought below the detection threshold (approx. mag. of 21-22).
Objects in GEO are only about 9.3% of the distance from Earth to Moon, though (35,786 kilometres , 22,236 miles v. 384,400 kilometres, 238,855 miles).

Considering the length of time of the exposures, and the considerable number of supposed transients, it seems (to me, intuitively- could be wrong) that some transients would be captured when, during the exposure, they end up entering the Earth's shadow or are just leaving it. Is this likely?
If so, might we expect to see a population of transients with an average magnitude lower than that of the general population, associated with being in shadow for a brief time during the exposure?

 

[JMartJr]

Just thinking, during a lunar eclipse, the Moon is still visible due to reflected light from the Earth because of refracted light in the atmosphere.
I appreciate that the transients are of very low magnitude, but might we expect some of the brighter transients to still be imaged?-
-though I guess they might all be brought below the detection threshold (approx. mag. of 21-22).
Objects in GEO are only about 9.3% of the distance from Earth to Moon, though (35,786 kilometres , 22,236 miles v. 384,400 kilometres, 238,855 miles).

Considering the length of time of the exposures, and the considerable number of supposed transients, it seems (to me, intuitively- could be wrong) that some transients would be captured when, during the exposure, they end up entering the Earth's shadow or are just leaving it. Is this likely?
If so, might we expect to see a population of transients with an average magnitude lower than that of the general population, associated with being in shadow for a brief time during the exposure?

If so, like an eclipsed moon, would they not be noticeably reddened/oranged? (If oranged is a word...)

 

[AmberRobot]

If so, like an eclipsed moon, would they not be noticeably reddened/oranged? (If oranged is a word...)

And extremely less bright. If they are barely visible in the POSS plates while sunlit they should be invisible in earth shadow. Just compare your camera settings when taking a photo of the moon versus a lunar eclipse.

 

[Eburacum]

It's worse than that, I think? The studies assume that most of the 100,000+ data points are objects in orbit (in a single hemisphere). For comparison, Starlink has under 10,000 nodes in orbit right now.

To get a statistically significant result that shows a deficit with the Earth's shadow., Villaroel et al. seem to have used these 106,339 data points. But they have already suggested that many or most of these data points are real stars which have moved over the intermediate decades.
That gives us two options.
1/ If these 106,339 data points are stars, then the deficit in the Earth's shadow must be nothing more than a coincidence due to the uneven distribution of stars in the sky.
2/ If these 106,339 data points are satellites, then there must have been tens of thousands of them up there, more than Musk has ever launched in his career.

The five thousand anomalies that cannot be identified with known stars are not enough to make the shadow effect significant, and they appear to be visible in the shadow plates anyway.

Are we to suppose that these 106,339 anomalies are also correlated with UAP reports and atom tests?

None of this makes sense.

 

[AmberRobot]

Agreed. It seemed like they said they used the whole Solano et al. sample, but didn't Solano say that only 5399 were unidentified? If so, then their analysis is contaminated by a majority of false positives it would seem. Am I misreading these papers?

 

[Mendel]

Agreed. It seemed like they said they used the whole Solano et al. sample, but didn't Solano say that only 5399 were unidentified? If so, then their analysis is contaminated by a majority of false positives it would seem. Am I misreading these papers?

Solano 2022 has a "candidate selection" chapter that identifies 298 165 sources by sampling the plates and then matching them with two other star surveys, and a geometrical criterium. What then follows are several sections of astronomical sleuthing that identifies more astronomical sources like IR stars or asteroids, and compares with a better scan of the same plates, and after that they ended up with a list of 5399 sources. Hambly & Blair have proposed that these remaining sources are emulsion defects, and @Eburacum has noticed above that they align somewhat with the edges of the plate grid, which is where (as we know from the paper that @NorCal Dave found) defects are more likely.

For the 2025 papers, it looks like they went with those 298165 transients, applied one IR star catalog to it, and left it at that. They also checked that the transients they used for the alignments were visible in the better scan.
The decision to go back on their earlier work and discard most of it is not explained.

 

[Mendel]

Just thinking, during a lunar eclipse, the Moon is still visible due to reflected light from the Earth because of refracted light in the atmosphere.
I appreciate that the transients are of very low magnitude, but might we expect some of the brighter transients to still be imaged?-

We're really looking for flares, which are specular reflections off a point source. If you've seen "Earth from space" footage, sunrise is really noticeable.

Considering the length of time of the exposures, and the considerable number of supposed transients, it seems (to me, intuitively- could be wrong) that some transients would be captured when, during the exposure, they end up entering the Earth's shadow or are just leaving it. Is this likely?

Yes. The chance for a teansient to be captured is (time outside shadow)/(exposure time).

If so, might we expect to see a population of transients with an average magnitude lower than that of the general population, associated with being in shadow for a brief time during the exposure?

No, because the glints are so short as to not leave streaks, so it's very unlikely that time spent in shadow would affect the brightness.

 

[Michael]

We're really looking for flares, which are specular reflections off a point source. If you've seen "Earth from space" footage, sunrise is really noticeable.

Yes. The chance for a teansient to be captured is (time outside shadow)/(exposure time).

No, because the glints are so short as to not leave streaks, so it's very unlikely that time spent in shadow would affect the brightness.

Glints would only be short if the relevant object is rotating (e.g. like a spin stabilised communication satellite). If a satellite isn't rotating then any glint it produced would last quite a while because the Sun spans 0.5 degrees in the sky (not a point source) so the glint beam would spread out from the satellite with a 0.5 degree angle (corresponding to ~350 km at 35,000 km distance). In other words, without rotation glints produced by satellites in high orbits would produce a streak (15 arcsec per second for geostationary).

 

[Mendel]

In other words, without rotation glints produced by satellites in high orbits would produce a streak (15 arcsec per second for geostationary).

Yeah, and any shape on the plates with ELONGATION<1.3 is filtered out in the "Candidate Selection" step of Solano 2022. Which means if an object is up to 2 arcseconds wide, it can't be longer than 2.6 arcseconds. In that case, the elongation might even be transverse to the direction of motion, as it would result from the superposition of a moving PSF over the exposure time: it would kinda look like the ellipse at the center of a simple Venn diagram.

 

[Mendel]

I did something in the other thread:

Then she does a great thing:

As a quick check, nevertheless, we also test by masking edge transients (>2° from plate center) to remove all artifacts close to the plate edge. Removing the edge of the plate in the analysis, yields a similar ∼30% deficit in Earth's shadow,

This is motivated by the grid pattern in the data that we've also found (after Hambly & Blair pointed it out), see e.g. https://www.metabunk.org/threads/digitized-sky-survey-poss-1.14385/post-355943 . And it proves that the shadow effect is bogus.
Note that the paper is skimpy on numbers here. The 2⁰ cut removes about half of the plate area (4⁰ vs. 6⁰ diameter, aka 16:36), but many more plate defects, since the grid pattern is caused by plate defects. So if there are orbital objects, the data should still have about 50% of these, but maybe only 10% of the plate defects. (I don't really know the number, but it's substantially less than 50%.) But the shadow deficit shrunk from 39% to 30%! It should have done the opposite!

We now know that the edge half of the plates has a stronger shadow deficit than the center half. This falsifies Villarroel's finding.

(more maths there)

Given that we've seen the edge grid, and that it's present in the 106339 data set (which it should, given that's also in the neoWISE data and the 5399), the shadow deficit cannot be explained by orbital objects. The data in the paper itself proves it.

 

[FatPhil]

I did something in the other thread:

(more maths there)

Given that we've seen the edge grid, and that it's present in the 106339 data set (which it should, given that's also in the neoWISE data and the 5399), the shadow deficit cannot be explained by orbital objects. The data in the paper itself proves it.

Unless you invoke ... weird aliens; this particular variety knows where the telescopes are pointing and when they're capturing images to make sure they don't step on the cracks.

 

[jdog]

I'm pretty much over this topic, but...

The more I see Avi Loeb glom onto everyone's else's work on 3I/Atlas and rush out preprints, the more sympathy I have with Villarroel, et.al. for not sharing their data before publication.

 

[jarlrmai]

I'm pretty much over this topic, but...

The more I see Avi Loeb glom onto everyone's else's work on 3I/Atlas and rush out preprints, the more sympathy I have with Villarroel, et.al. for not sharing their data before publication.

They shared and publicised the pre-print on archivx a while before peer review

 

[FatPhil]

I'm pretty much over this topic, but...

The more I see Avi Loeb glom onto everyone's else's work on 3I/Atlas and rush out preprints, the more sympathy I have with Villarroel, et.al. for not sharing their data before publication.

Villarroel is, or at least was, part of Loeb's Galileo project:

Det nystartade forskningsprojektet Galileo har fått 15 miljoner kronor för att vetenskapligt undersöka och leta efter tecken på utomjordisk aktivitet på jorden. Den svenska forskaren Beatriz Villarroel vid Stockholms universitet ingår i den internationella forskargruppen och vi på Populär Astronomi har pratat med henne om projektet.

-- https://www.popularastronomi.se/202...ojekt-om-sokande-efter-utomjordisk-aktivitet/
Which deepl turns into:

The newly launched Galileo research project has received SEK 15 million to scientifically investigate and search for signs of extraterrestrial activity on Earth. Swedish researcher Beatriz Villarroel at Stockholm University is part of the international research team, and we at Populär Astronomi spoke with her about the project.

So it would be surprising if she's trying to protect her work from him.

 

[Mendel]

I'm pretty much over this topic, but...

The more I see Avi Loeb glom onto everyone's else's work on 3I/Atlas and rush out preprints, the more sympathy I have with Villarroel, et.al. for not sharing their data before publication.

She's published now, though, so where's the data?

 

[Scaramanga]

That's a good point. Satellites in LEO would fall into the shadow of the Earth for many minutes every orbit; satellites halfway to GEO would fall into the Earth's shadow much less frequently, and satellites in GEO would only fall into shadow for a few minutes during certain segments of their orbit in certain months of the year. For the vast majority of their orbit they would be in full sunlight.

However - satellites in LEO are moving very rapidly, with a motion that is easy to see even with the naked eye. Any satellite in LEO would make an elongated trace (a blur) on the photograph, depending on how long the exposure is.

On the other hand satellites in GEO would be motionless with respect to the Earth, and so they would be motionless with respect to the tracking of the telescope, which would presumably be moving in order to compensate for the rotation of the Earth. Do we have any information about how long each of these exposures were? Unless the exposure time was very short indeed, we should see any LEO satellites as elongated blurs, and the blur would get shorter and shorter as the satellite orbit approaches GEO.

Note that even a satellite in GEO would move with respect to the fixed stars unless it was in an equatorial orbit (which is a relatively minute fraction of the sky).

But why are we discussing satellites as an explanation for photos taken in 1952 ? There were no satellites in 1952.

 

[Mendel]

But why are we discussing satellites as an explanation for photos taken in 1952 ? There were no satellites in 1952.

Please read the paper. https://iopscience.iop.org/article/10.1088/1538-3873/ae0afe posits that there may have been "non-human artificial objects" or "extraterrestrial probes" in orbit at the time.

 

[overlord]

But is it?

@NorCal Dave found* a paper published in November 1956** that describes a better method to process the 103a-O photos; given publication timelines in pre-Internet days, I find it not at all unlikely that the process (if not the emulsion itself) had improved after March 1956, in the months when no photos were taken.

---

* https://www.metabunk.org/threads/transients-in-the-palomar-observatory-sky-survey.14362/post-355721
** https://adsabs.harvard.edu/full/1956AJ.....61..399G

I should have ended my comment more clearly but my train of thought got severely sidetracked by the dates and times used in the paper and their accuracy. I'll try again in brief:

Villarroel reports a lack of "transients in nuclear test window" after 1956-03-17.
The explanation for this is that plates were taken on only a handful of dates in that period. There is no need for any other explanation for this.

"transients disappeared" and "saw less transients" are either direct or indirect misinterpretations of Villarroel's statement and therefore need no explanation.
And the 'explanations' offered are either unsupported or false.

See my above comment for the actual quotes:

[↑]

But very well, I have now read the quoted paper (https://adsabs.harvard.edu/full/1956AJ.....61..399G - 'Gollnow and Hagemann (1956)' , click on 'print this article' for a proper pdf view).

The results in figure 1 offer limited statistical power:

Article:

Two plates of each kind were tested. The means are plotted in Figure 1 [...]

The 'DSS' scans of 'POSS-I' have a pixel size of about 25μm (14x14 inch plates (+ a bit of border) to 14000x14000 pixels).
From 'Solano et al. (2022)':

Article:

[candidate selection (v.)]
Our condition forces the source to be larger than one pixel and of similar size in both directions.

Source: https://academic.oup.com/mnras/article/515/1/1380/6607509

All numbers in 'Gollnow and Hagemann (1956)' aside from the single data point in the above chart are below 25μm.
But more importantly they are talking about the displacement / distortion of the exposed image (in the plane of the plate), not about the appearance of misleading 'star like flaws'. (Note that I'm perfectly aware of the presence of emulsion flaws on 'POSS-I' plates, just like the people doing the survey were, but that's not relevant here.)

I think that this paper has very limited relevance to the works by Villarroel et al.

 

[Mendel]

References

Villarroel 2025a
Aligned, Multiple-transient Events in the First Palomar Sky Survey
Beatriz Villarroel et al 2025 PASP 137 104504 DOI 10.1088/1538-3873/ae0afe
https://iopscience.iop.org/article/10.1088/1538-3873/ae0afe was published October 17. It's about 83 claimed (5 demonstrated) motion lines and the shadow effect, and based on a 106,339 transient sample.

Villarroel 2025b or Bruehl 2025
Bruehl, S., Villarroel, B. Transients in the Palomar Observatory Sky Survey (POSS-I) may be associated with nuclear testing and reports of unidentified anomalous phenomena. Sci Rep 15, 34125 (2025). https://doi.org/10.1038/s41598-025-21620-3
https://www.nature.com/articles/s41598-025-21620-3 was published October 20. It's about correlating transient observation dates with UFO reports and nuclear tests, and based on a 107,875 transient sample.

Solano 2022
Enrique Solano, B Villarroel, C Rodrigo, Discovering vanishing objects in POSS I red images using the Virtual Observatory, Monthly Notices of the Royal Astronomical Society, Volume 515, Issue 1, September 2022, Pages 1380–1391, https://doi.org/10.1093/mnras/stac1552
https://academic.oup.com/mnras/article/515/1/1380/6607509?login=false
"Working with three large-area sky surveys (POSS I, Gaia EDR3 and Pan-STARRS DR2) and a workflow based on VO archives and services, we have searched for sources identified in POSS I but not seen either in Gaia or Pan-STARRS finding 298 165 sources. After filtering sources found in other archives (mainly in the infrared), asteroids, high proper motion objects with no information on proper motion in Gaia EDR3, known variables and artefacts, we ended up with a list of 5399 sources."
The list of 5399 transients is available at http://svocats.cab.inta-csic.es/vanish/ .

I should point out that Villarroel 2025a also uses the 107,875 transient data set for the plate-based analysis, with a different number of transients for the 80Mm altitude shadow.

 

[Mendel]

Article:

A Cost-Effective Search for Extraterrestrial Probes in the Solar System Open Access
Beatriz Villarroel, Wesley A Watters, Alina Streblyanska, Enrique Solano, Stefan Geier, Lars Mattsson
Monthly Notices of the Royal Astronomical Society, staf1158, https://doi.org/10.1093/mnras/staf1158
Published: 04 August 2025

Abstract

For centuries, astronomers have discussed the possibility of inhabited worlds — from Herschel's 18th-century observations suggesting Mars may host life, to the systematic search for technosignatures that began in the 1960s using radio telescopes. Searching for artifacts in the solar system has received relatively little formal scientific interest and has faced significant technical and social challenges. Automated surveys and new observational techniques developed over the past decade now enable astronomers to survey parts of the sky for anomalous objects. We briefly describe four methods for detecting extraterrestrial artifacts and probes within the Solar System and then focus on demonstrating one of these. The first makes use of pre-Sputnik images to search for flashes from glinting objects. The second method makes use of space-borne telescopes to search for artificial objects. A third approach involves examining the reflectance spectra of objects in Earth orbit, in search of the characteristic reddening that may imply long-term exposure of metallic surfaces to space weathering. We focus here on a fourth approach, which involves using Earth's shadow as a filter when searching for optically luminous objects in near-Earth space. We demonstrate a proof-of-concept of this method by conducting two searches for transients in images acquired by the Zwicky Transient Facility (ZTF), which has generated many repeated 30-second exposures of the same fields. In this way, we identified previously uncatalogued events at short angular separations from the center of the shadow, motivating more extensive searches using this technique. We conclude that the Earth's shadow presents a new and exciting search domain for near-Earth SETI.

Source: https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/staf1158/8221885

 

[MonkeeSage]

Dr. Villarroel made this rather interesting statement on X today.

The biggest mistake by anyone who dismisses the transients as emulsion defects is thinking this solves the problem. If all transients were proven to be emulsion defects, the anomaly wouldn't disappear — it would move from observational astronomy to psi research. One would then have to explain why supposedly local, random processes in photographic emulsions systematically avoid Earth's shadow, and correlate with major events such as nuclear bomb tests or waves of UFO sightings.

Source: https://x.com/DrBeaVillarroel/status/2003122714291146866