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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Cosmic ray visual phenomena | 1/3 | https://en.wikipedia.org/wiki/Cosmic_ray_visual_phenomena | reference | science, encyclopedia | 2026-05-05T12:33:22.738898+00:00 | kb-cron |
Cosmic ray visual phenomena, or light flashes (LF), also known as Astronaut's Eye, are spontaneous flashes of light visually perceived by some astronauts outside the magnetosphere of the Earth, such as during the Apollo program. While LF may be the result of actual photons of visible light being sensed by the retina, the LF discussed here could also pertain to phosphenes, which are sensations of light produced by the activation of neurons along the visual pathway.
== Possible causes == Researchers believe that the LF perceived specifically by astronauts in space are due to cosmic rays (high-energy charged particles from beyond the Earth's atmosphere), though the exact mechanism is unknown. Hypotheses include Cherenkov radiation created as the cosmic ray particles pass through the vitreous humour of the astronauts' eyes, direct interaction with the optic nerve, direct interaction with visual centres in the brain, retinal receptor stimulation, and a more general interaction of the retina with radiation.
== Conditions under which the light flashes were reported == Astronauts who had recently returned from space missions to the Hubble Space Telescope, the International Space Station and Mir Space Station reported seeing the LF under different conditions. In order of decreasing frequency of reporting in a survey, they saw the LF in the dark, in dim light, in bright light and one reported that he saw them regardless of light level and light adaptation. They were seen mainly before sleeping.
== Types == Some LF were reported to be clearly visible, while others were not. They manifested in different colors and shapes. How often each type was seen varied across astronauts' experiences, as evident in a survey of 59 astronauts.
=== Colors === On Lunar missions, astronauts almost always reported that the flashes were white, with one exception where the astronaut observed "blue with a white cast, like a blue diamond." On other space missions, astronauts reported seeing other colors such as yellow and pale green, though rarely. Others instead reported that the flashes were predominantly yellow, while others reported colors such as orange and red, in addition to the most common colors of white and blue.
=== Shapes === The main shapes seen are "spots" (or "dots"), "stars" (or "supernovas"), "streaks" (or "stripes"), "blobs" (or "clouds") and "comets". These shapes were seen at varying frequencies across astronauts. On the Moon flights, astronauts reported seeing the "spots" and "stars" 66% of the time, "streaks" 25% of the time, and "clouds" 8% of the time. Astronauts who went on other missions reported mainly "elongated shapes". About 40% of those surveyed reported a "stripe" or "stripes" and about 20% reported a "comet" or "comets". 17% of the reports mentioned a "single dot" and only a handful mentioned "several dots", "blobs" and a "supernova".
== Motion == A reporting of motion of the LF was common among astronauts who experienced the flashes. For example, Jerry Linenger reported that during a solar storm, they were directional and that they interfered with sleep since closing his eyes would not help. Linenger tried shielding himself behind the station's lead-filled batteries, but this was only partly effective. The different types of directions that the LF have been reported to move in vary across reports. Some reported that the LF travel across the visual field, moving from the periphery of the visual field to where the person is fixating, while a couple of others reported motion in the opposite direction. Terms that have been used to describe the directions are "sideways", "diagonal", "in-out" and "random". In Fuglesang et al. (2006), it was pointed out that there were no reports of vertical motion.
== Occurrences and frequencies == There appear to be individual differences across astronauts in terms of whether they reported seeing the LF or not. While these LF were reported by many astronauts, not all astronauts have experienced them on their space missions, even if they have gone on multiple missions. For those who did report seeing these LF, how often they saw them varied across reports. On the Apollo 15 mission all three astronauts recorded the same LF, which James Irwin described as "a brilliant streak across the retina".
=== Frequency during missions === On Lunar missions, once their eyes became adapted to the dark, Apollo astronauts reported seeing this phenomenon once every 2.9 minutes on average. On other space missions, astronauts reported perceiving the LF once every 6.8 minutes on average. The LF were reported to be seen primarily before the astronauts slept and in some cases disrupted sleep, as in the case of Linenger. Some astronauts pointed out that the LF were seemingly perceived more frequently as long as they were perceived at least once before and attention was directed to the perception of them. One astronaut, on his first flight, only took note of the LF after being told to look out for them. These reports are not surprising considering that the LF may not stand out clearly from the background.