Intersidereal is a word that refers to the space between celestial bodies. Some synonyms for this word include interstellar, astral, cosmic, stellar, and heavenly. Interstellar is a commonly used synonym, especially when referring to travel or communication between stars or galaxies. Astral and cosmic are similar in meaning, often used to describe space and the stars within it. Stellar most often refers to the stars themselves and their characteristics. Heavenly, on the other hand, is more often used in a religious or spiritual context. Regardless of the synonym chosen, all relate to the vast expanse of space beyond our own planet.