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.