Transients in the Palomar Observatory Sky Survey

[John J.]

has Villarroel indicated at any point that they have reached out to the "custodians of the plates" to ask for access and if so have they reported the response?

I don't know. Maybe others do, but I don't remember Beatrix Villarroel suggesting this (which doesn't mean she hasn't).

I guess many other astronomers have done work based on/ informed by DSS and/or SSS, and probably the earlier glass POSS1 copies (perhaps more so pre-digitisation). If this is the case, it might be argued that those astronomers were not obliged to refer back to the original material (conjecture, maybe some were, I don't know). But I feel B.V. et al.'s transient papers are perhaps different; their findings are extraordinary and if accepted their implications are far-reaching. Hambly and Blair have raised what might be plausible concerns about reprographic artefacts, which might be tested by examining the POSS1 plates. Maybe other relevant insights would be made while examining the originals.

I don't know anything about access to the POSS1 plates. Even if allowed, a re-examination of the 1st generation plates (presumably "in situ") might be a much more time-consuming, inconvenient and in effect expensive process than the study of the digitised material.

 

[jon_eir]

I don't think they have actually examined the original plates. However I think they would say they have shown that the transients can't be emulsion artifacts because their distribution has been shown to correlate with the Earth's shadow. But even that logic has been shown to have some questionable assumptions and tenuous rationale.

Snips from my post #72:

To me having not looked at these papers in 2 years nothing seems to have moved on. Like you said all the assumptions made around why these may not be plate artifacts seem flawed either,

1-address the issues the authors themselves highlighted in the 2021 paper
or
2-clearly state the problem or the assumptions being made on those issues in future papers

Completely pointless discussing/building on the initial work without this. Go make some plates again and do a study on that even to further the conversation.

 

[AmberRobot]

I don't know. Maybe others do, but I don't remember Beatrix Villarroel suggesting this (which doesn't mean she hasn't).

to me, it seems a major oversight to not examine the originals, and if she had tried and was rejected that would be an important point to make in order to show that one is trying in good faith to rule out an instrumental artifact. It seemed like she just said "I don't have access to the originals" and then carried on leaving the uncertainty just hanging over the entire work.

 

[jdog]

to me, it seems a major oversight to not examine the originals, and if she had tried and was rejected that would be an important point to make in order to show that one is trying in good faith to rule out an instrumental artifact. It seemed like she just said "I don't have access to the originals" and then carried on leaving the uncertainty just hanging over the entire work.

Properly assessing the original plates -- especially dealing with any significant number of suspected transients -- would have to be done by someone with expertise in glass-plate astrophotography. Probably someone working at the one of the several astronomical archives holding glass plate collections, like Harvard College Observatory or the Carnegie Plate Archives.

 

[AmberRobot]

Properly assessing the original plates -- especially dealing with any significant number of suspected transients -- would have to be done by someone with expertise in glass-plate astrophotography. Probably someone working at the one of the several astronomical archives holding glass plate collections, like Harvard College Observatory or the Carnegie Plate Archives.

And that could in principle be done in collaboration with Villarroel but there's no indication that I have seen that this was attempted.

 

[NorCal Dave]

Properly assessing the original plates -- especially dealing with any significant number of suspected transients -- would have to be done by someone with expertise in glass-plate astrophotography. Probably someone working at the one of the several astronomical archives holding glass plate collections, like Harvard College Observatory or the Carnegie Plate Archives.

And may have been a bit of a wild goose chase before. But her most recent paper has identified 203 transients on plate(s) from 1 particular day, 5/3/1954:

To maximize likelihood of interpretable results, we again focused on the highest probability transients (≥ 0.90 probability of being a real transient per the ML model) [10].There were 231 transients meeting this criterion observed within +/- 1 day of a nuclear test(for nuclear testing details, see https://nnss.gov/wp-content/uploads/2023/08/DOE_NV209_Rev16.pdf). Of these, 203 transients (87.9%) were associated with a single nuclear test:Castle Yankee conducted on 5/4/54.

In addition, these transients are supposedly located in particular spots over the Eastern Pacific, off the coast of Mexico:

Cluster 1 was centered in the Pacific ocean to the southwest of Baja California. Clusters 5 and 6, while statistically distinct, were located in two adjacent regions of the Pacific further south than Cluster 1, with both being to the west of southern Mexico and Central America. These two clusters combined represented the location of nearly 65% of all high probability transients identified.

https://arxiv.org/pdf/2609.09461

So, there is a plate(s) from a particular day that has 203 transients in a particular area on it. That would substantially narrow down what to look for on the specific original plate(s). As there is a specific plate(s), it should also be easier to track the copy(s) from original to digitization thus providing a complete pipeline that can be checked for transients. Right?

 

[AmberRobot]

What does it mean for a transient to be "over" a particular location on Earth? Aren't these supposed to be in space? Is that point on Earth just the "sub-satellite" point (i.e., draw a line from the supposed location of the transient to the center of the earth and where it intersects the surface)? It seems odd to geolocate a transient happening in space, especially when there's no direct measurement of the 3-d position of the supposed object. A transient by its nature is not repeating, which means no ephemeris can be calculated and an altitude would have to be assumed, no?

sorry, I am not well versed in all of this research, so perhaps these questions have been addressed in the papers and/or this thread. I can be ignored if I am rehashing old ground.

 

[NorCal Dave]

What does it mean for a transient to be "over" a particular location on Earth? Aren't these supposed to be in space? Is that point on Earth just the "sub-satellite" point (i.e., draw a line from the supposed location of the transient to the center of the earth and where it intersects the surface)? It seems odd to geolocate a transient happening in space, especially when there's no direct measurement of the 3-d position of the supposed object. A transient by its nature is not repeating, which means no ephemeris can be calculated and an altitude would have to be assumed, no?

sorry, I am not well versed in all of this research, so perhaps these questions have been addressed in the papers and/or this thread. I can be ignored if I am rehashing old ground.

The geolocation thing, as well as the supposed altitude of transient being calculated from the POSS1 plates is from her new pre-print that I linked to. Whether it works or not, I have no idea. But I would think one could try to follow the logic and find a particular area on the plate that the authors believed was above certain location on the Earth. In this case, a number of points in the Eastern Pacific:

Because the shadow deficit is consistent with transients representing reflective objects in Earth orbit and recent findings suggest transients may be due to brief flashes like tumbling objects in orbit exhibit [12.14], we began exploring their potential orbital parameters. We recently developed a modelling approach that permits estimating the altitude of POSS-I transients based on shadow deficit characteristics [12]. Results using two complementary statistical approaches both suggested that transients were between 26,371 - 35,786 km above Earth.

After filtering for high probability transients, results were most consistent with the higher estimate, suggesting geosynchronous orbit. Notably, a significant excess of transients was observed at low declinations [12], potentially indicating orbits near the celestial equator where modern geosynchronous satellites are typically observed [15].

Building on these recent findings, the current work explored the Earth-projected locations over which transients were observed. Specifically, given an assumed orbital altitude of 35,786 km, combined with information regarding the Mount Palomar observatory location and observation parameters (e.g., right ascension, declination), we estimated the latitude and longitude over which transients were positioned at the time POSS-I transient images were taken.

At least it narrows down a particular date and possible location on a plate(s) from that date for examination.

The new pre-prints may need a new thread.

 

[jon_eir]

In addition, these transients are supposedly located in particular spots over the Eastern Pacific, off the coast of Mexico:

can I ask the transients on what plate?, how was that plate produced? was it a first generation negative that was used to make a positive and that positive was used to make how many copies? these copies seen to have produced in batches and record keeping of copies seems to have been poor on the whole.

maybe link the paper that you quoted from in this instance-were any of the plates issuses that have been mentioned in the paper or why they might not apply to this plate in particular?

 

[John J.]

But her most recent paper has identified 203 transients on plate(s) from 1 particular day, 5/3/1954... ...In addition, these transients are supposedly located in particular spots over the Eastern Pacific, off the coast of Mexico

Rough map showing the location of the Castle Yankee nuclear test, 05 May 1954, and proposed transient "hotspots"
(Fig. 2, "Earth-Projected Clustering of Historical Optical Transients in the Palomar Observatory Sky Survey-I (POSS-I)", Bruehl, Villarroel et al.)

Not all contributing transients would be on this date, but Bruehl, Villarroel et al. write

Of these, 203 transients (87.9%) were associated with a single nuclear test: Castle Yankee conducted on 5/4/54.

The map is very approximate as the projections used differ. Point C4 in SW Canada is not shown.

Bruehl, Villarroel et al:

It is notable that these 203 transients were all observed the night immediately before this test and were located exclusively over Pacific hotspot regions west of Mexico and Central America identified in hostpot analyses described above. None were observed over the southwestern U.S. or in the Gulf of Mexico region.

If the Oschin Schmidt telescope was not facing East to take photos for POSS1 on 04 May, the lack of transients over the Gulf of Mexico would not be a surprise. Transients will only be apparent in areas of sky being imaged at the time.

I wonder if more transients at lower latitudes (and higher, e.g. C4 in British Columbia) might correlate with positions of apparent transients on the plates? IIRC significantly more transients were detected near plate edges.

 

[AmberRobot]

The geolocation thing, as well as the supposed altitude of transient being calculated from the POSS1 plates is from her new pre-print that I linked to. Whether it works or not, I have no idea. But I would think one could try to follow the logic and find a particular area on the plate that the authors believed was above certain location on the Earth. In this case, a number of points in the Eastern Pacific:

Sure. But if I were an alien in a spacecraft at geostationary altitude where I could see almost the entirety of the Pacific at once I question the meaningfulness of assigning a specific latitude and longitude as being "under" the spacecraft.

 

[NorCal Dave]

can I ask the transients on what plate?, how was that plate produced? was it a first generation negative that was used to make a positive and that positive was used to make how many copies? these copies seen to have produced in batches and record keeping of copies seems to have been poor on the whole.

maybe link the paper that you quoted from in this instance-were any of the plates issuses that have been mentioned in the paper or why they might not apply to this plate in particular?

Link to the paper I quoted from is right there under the graph, but I'll link again:

https://arxiv.org/pdf/2609.09461

As to which plate(s) and how they were produced, it's sorta been covered. I think you read the first paper on this subject where they explain they used digitized scans that trace back to the original POSS 1 photographic plates produced at the Palomar Observatory. This new paper uses the same sources.

To be clear, Villarreol et al. don't mention or specify any specific plate in the paper, which is consistent with all of the related papers as far as I know. They used various techniques to analyze digitized versions of the POSS 1 plates and identified "transients" as has been discussed. But it was never clear what transients are found on which digitized plates. That data seems to be unavailable or hard to understand.

As you pointed out up-thread, the digitized versions were often from at least 2nd or more generations of photographic copies, so not only should the originals be examined, but each successive copy between the originals and the digitizing process should also be examined. This becomes quite a daunting task when there is no clear explanation as to which original plates and subsequent copies, supposedly contain which transients. Add to this the delicate nature of the originals which makes them difficult to access.

However, in the new paper a specific date is given for a digitized plate(s) that contains 203 transients related to a nuclear test on May 4, 1954. It appears plates were produced on May 3 and May 5 of 1954. With the test happening on the other side of the date line, the May 3 digitized plate(s) is likely the one.

So, someone now has a specific plate to look at. Even if the original plates are hard to access, there is potentially 1 specific plate(s) to look at. That's 1 plate(s) from 1 night that supposedly contains 203 transients. It narrows down where to look for transients on the originals. And, with one specific plate(s) it might be easier to trace the copies from that plate that led to the digitized versions used in the paper.

In addition, if one can understand their geo-location strategy, regardless if it's wrong or right, it can tell someone where to look for the 203 transients on the 1 specific plate(s). Someone now knows where to look for 203 transients.