1. the sides of celestial bodies that face away from the sun and are in darkness
Usage: astronomy

Examples

• The nightsides of planets receive no direct sunlight.
• Scientists study temperature differences between the daysides and nightsides of exoplanets.
• The nightsides of tidally locked planets remain permanently dark.
• Infrared telescopes can detect heat radiation from planetary nightsides.
• The nightsides of moons often experience extreme cold.
• Atmospheric circulation patterns differ greatly between daysides and nightsides.