True polar night

A true polar night is a period of continuous darkness where no astronomical twilight occurs at the solar culmination. Astronomical twilight happens when the Sun is between twelve and eighteen degrees below the horizon and night happens when it is lower than that. Thus, the true polar night is limited to latitudes above roughly 84° 34', which is exactly 18° within the polar circles, or approximately five and a half degrees from the poles. The only permanent settlement on Earth above this latitude is Amundsen–Scott South Pole Station, the South Pole scientific research station, whose winter personnel are completely isolated from mid-February to late October. During a true polar night, stars of the sixth magnitude, which are the dimmest stars visible to the naked eye, will be visible throughout the entire 24 hour day. This happens when the sun is between exactly 18° and approximately 23° 26' below the horizon. These conditions last about 11 weeks at the poles.

South Pole, Antarctica experiences this from May 11 to August 1.[13]

The North Pole experiences this from November 12 to January 28.[14][15]