Abstract
This study aimed to address the unexplored relaxing effects of stargazing with different night sky darknesses in a planetarium by conducting an experiment to investigate the physiological effects of the relaxation/stress state on brain and autonomic nervous system activity, as well as the psychological healing effects. Five healthy young women participated in our experiment. We conducted physiological measurements of oxygenated hemoglobin (OxyHb) concentration in the left and right prefrontal cortices by near-infrared spectroscopy, heart rate variability as a measure of the relaxation/stress state, and a psychological assessment of healing on an 11-point Likert scale. We used 9 types of stimuli: 6-star image stimuli that imitated dark star fields (low light pollution) to bright night sky (high light pollution), and movie stimuli that were viewed daily. The results showed that (1) visual stimulation with images of dark night sky significantly reduced the concentration of OxyHb in the right prefrontal cortex and (2) the psychological rating of healing was significantly higher compared to bright night sky. The results of this study will help solve the problems of the mental and physical effects of light pollution on astronomical observations and the reproduction of star images in planetariums.