KAERO: Novinky o defektech v emulzi
Fast Astronomical Transients in Archival Photographic Plates: Using optical aberrations as a tool for discerning real images, from plate artifactshttps://arxiv.org/html/2606.08319Abstract
The detection of fast astronomical transients in photographic plates from the Palomar sky surveys conducted in the 1950s, was subject to the criticism that such transients could be just the effect of otherwise unaccounted for plate artifacts. In this paper, we show that transient images exhibit the coma aberration pattern expected from off-axis point sources recorded through the telescope optics, a signature that plate artifacts cannot naturally reproduce. Although the data does not by themselves establish the physical origin of the light that generated the images, they lend support to hypotheses that do not rely on instrumental effects to explain transients.
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Data from the Hamburger Sternwarte Doppel-Reflektor 0.6-m parabolic mirror telescope was selected for this project, because its images are affected by significant coma, and because enough plate pairs appropriate for the transient search could be found at the archive holdings.
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Asteroids can be ruled out as the cause of these transients, however, since no blurring is visible on the 10 min. long exposures, and the distance travelled is inconsistent with typical asteroid speeds. The Minor Planet Center asteroid finding tool also returns empty for both date, time, coordinates data sets.
Following the above, on March 4, 1951, three very bright events were recorded again on the same patch of sky as the ones described above (Figures 2, 3, 4 and 6). Of note is the fact that the photographic image of the brightest event shows evidence of saturation of the emulsion response to light, and halation, the result of light backscatter in the emulsion layer. These further confirm that the image resulted from light acting on the emulsion, and not a plate defect.
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The data set consists of 525 plates produced by the Hamburger Sternwarte Doppel-Reflektor 0.6-m telescope, during the period 1934 to 1957. That telescope creates images that are mildly affected by coma. Using a slightly modified methodology as the one presented in Paper I, we found eleven transients on that data set.
The transients exhibit a remarkable degree of clustering, both in time as in space. All eleven showed up on only two small regions of the sky, even when appearing on separate nights. They also all happened in the period 1949 - 1953, even though the data set has about half of its plate pairs outside that window.
Explanations for the transient phenomenon were advanced by several authors. Hyphotheses based on plate artifacts (Hambly and Blair, 2024) are not supported by the findings in this work, although we still need to further develop the comatic-image technique with better sampling and an automated identification algorithm.
Other hypothesis based on non-astronomical causes for these transients still exist (the astronomical ones were examined by Solano et al. 2022). Villarroel et al. 2021 shows that micrometeorites seen face-on are not a good explanation. Ghosting and internal reflections on the optics can be dismissed by the fact the present work relies on pairs of plates: if ghosting from star images in the field happened, it should show up on both plates and thus be automatically excluded from the results. Hypotheses based on little-known upper atmosphere effects still need to be further developed.
However, the data presented here are consistent with two non-astronomical hypotheses advanced in recent years. Although the plate sample is not complete and homogeneous enough for us to draw a statistically meaningful conclusion, the data is consistent with the association that Bruehl and Villarroel (2025) found to exist between transients and nuclear weapon testing. On the same token, the data are also consistent with the hypothesis that these transients may be Sunlight glints generated by tumbling, mirror-like objects in space, in the vicinity of Earth (Villarroel et al., 2025b).