Did an Astronomical Photographic Plate From 1950 (Seven Years Before Sputnik) Show Artificial Satellites?

I just discovered this (possible) astronomical mystery while watching the video entitled 10 Unsettling Alien Technosignatures that Could be Very Close by author and futurist John Michael Godier.

Synopsis:

The first potential “techno-signature” Godier describes is entitled Transients in Photographic Plates.

It is based upon a recent paper entitled “Is there a background population of high-albedo objects in geosynchronous orbits around Earth?” Villaroel et al, 2022 by Beatriz Villarroel.

In April 1950, astronomers noticed that nine starlike point sources of light had simultaneously appeared in a photographic plate. This occurred during the Palomar Sky Survey at the Palomar Observatory in Southern California.

None of those point sources appeared in plates taken before or after. Images taken today also do not show the nine point sources.

Beatriz Villarroel at the Nordic Institute for Theoretical Physics in Stockholm, Sweden, and colleagues have tried to answer the question what were these nine transient objects?

The paper claims that a photographic plate from 1950 shows tracks consistent with artificial satellites. The tracks are consistent with objects in a geosynchronous orbit.

Humans (to our knowledge) did not successfully orbit a satellite until Sputnik was launched in late 1957. Placing a satellite in geosynchronous orbit was not achieved until 1963.

The objects on the photographic plate also appeared to be rotating as a geometrically shaped (i.e. non-natural) satellite would.

Alternative Explanations:

Instruments? Perhaps the anomalies were akin to lens flares? While the glass cover used during scanning could produce false stars, the objects in the photographic plate do not have the shape expected from such an image.

Elementary particles? Muons and natural radioactivity were ruled out since such particles hit photographic plates at a steady rate. I.e. had this happened, the photographic plates would have been full of false stars.

Alpha particles, beta particles or gamma rays can alter photographic plates. However, since the first atomic bomb test in July 1945, new containers were created by Kodak to prevent this (radioactive contaminants from to atom bomb test left tiny fogged spots on photographic plates).

Human error? Humidity or tiny droplets from sneezing or saliva could leave traces on photographic plates, but do not produce circular shapes on a flat surface (they are elongated and clustered).

In addition, water droplets have more variability in size than what is seen in the plates.

Naturally occurring transients? This case shows nine simultaneous transients within a 30-minute period and within a small section of sky. But the total density of naturally occurring fast transients such as flaring stars, gamma-ray bursts or fast radio bursts is estimated to be about 1.63 events per square degree per day.

Asteroids or meteoroids? This was considered unlikely, since any such fragments would be moving in space.

For a meteoroid to appear as a point source, it would need to burn up in less than a millisecond (or else it would appear as a streak).

Airplanes or satellites? Although an airplane’s strobe might cause this type of image, airplanes also have lights that are on continuously – which would show as a streak.

While rotating satellites or debris in geosynchronous orbits can produce similar point sources like those seen in the plates, no known satellites were in orbit at that time.

Conclusion:

From the paper:

A follow-up critique showed that the … transient is more likely explained by a solar system satellite of artificial or natural origin. Small, flat and highly reflective objects at, or near, geosynchronous orbits around the Earth could produce multiple, fast glints.

Questions: