noun
sphere of fixed stars
Historical astronomical term from the Ptolemaic system; refers to the outermost celestial sphere where the fixed stars were thought to be embedded. Rare in modern usage, mainly encountered in historical or academic contexts.
プトレマイオスの宇宙論では、恒星天は宇宙の最外層に位置していた。
In Ptolemaic cosmology, the sphere of fixed stars was located at the outermost layer of the universe.
天球 is the general concept of the celestial sphere in astronomy, while 恒星天 specifically refers to the sphere of fixed stars in the Ptolemaic model.
Compound of 恒星 (fixed star) and 天 (heaven, celestial sphere). The term is a direct translation of the Western astronomical concept 'sphere of fixed stars'.