noun which may take the genitive case particle 'no'
interstellar
Used attributively with の to modify nouns, as in 恒星間旅行 (interstellar travel).
恒星間航行はまだ実現していない。
Interstellar navigation has not yet been realized.
恒星間物質の研究が進んでいる。
Research on interstellar matter is advancing.
惑星間 means 'interplanetary', referring to space between planets within a star system, while 恒星間 refers to space between stars.
Compound of 恒星 (star) + 間 (between).