dome of the sky; vault of heaven
Formal, literary term for the overarching sky or heavens, often with a poetic or classical feel. Rare in everyday speech.
The stars in the vault of heaven shone quietly.
A Sino-Japanese compound of 穹 (kyū, 'dome' or 'vault') and 蒼 (sō, 'blue' or 'azure'). The exact historical derivation is uncertain, but the spelling is conventionally associated with the poetic image of the sky as a vast blue dome.