What causes astronauts outside a spacecraft to occasionally perceive a brief flash of light?

Answer

The particle exciting molecules in the retina or generating Cherenkov radiation in eye fluid

This visual phenomenon is attributed to the ionizing particle exciting the molecules within the retina or generating Cherenkov radiation within the fluid of the eye as it travels faster than light in that medium.

What causes astronauts outside a spacecraft to occasionally perceive a brief flash of light?

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