【Celestial】 , 【heavenly】 , 【empyrean】 , 【empyreal】 mean of, relating to, or fit for heaven or the heavens.

【Celestial】  (opposed to terrestrial) may refer either to the visible heavens (the region surrounding the earth and seemingly enclosed by the sky) or to the religious conception of heaven or the heavens (in Christian use, the abode of God, the angels, and the blessed dead); thus, a 【celestial】 globe is one on whose surface the stars, planets, comets, and nebulae are depicted; a 【celestial】 body is a star, planet, or other aggregation of matter that forms a unit for astronomical study; a 【celestial】 visitant is an angel or other spirit from the spiritual heaven; 【celestial】 bliss is the happiness enjoyed by the residents of heaven.

【Heavenly】 , although it is applicable, especially in nontechnical use, to the visible heavens or to pagan conceptions of Olympus or other abodes of the gods is far more often applied to heaven as conceived by Jews and Christians and is apt, therefore, to suggest spiritual qualities.

【Empyrean】 and 【empyreal】 suggest association with the  【empyrean】 , either as thought of in ancient and medieval cosmology as the highest 【celestial】 sphere, a region of light or fire or, more often, as conceived by various theologians and poets as the highest of the spiritual heavens, where God is and reigns in spiritual light the fire.

The words are often weakened in idiomatic use to mean little more than outstanding of its kind.