"Planet-struck" is an uncommon word that describes someone who is deeply fascinated and entranced by planets and outer space. However, there are several synonyms that convey similar meanings. Words like "cosmic-minded", "starstruck", or "space-obsessed" all convey the idea of being enamored by the mysteries and wonders of the universe. These words are often used to describe people who are passionate about astronomy, astrology, or science fiction. Additionally, words like "galactic", "celestial", or "interstellar" can also be used to describe the fascination with the vastness of space and all its unknown mysteries. Whether it's exploring the cosmos or simply admiring the beauty of the night sky, there are plenty of words to describe someone who is planet-struck.