This is a list of Planet related discoveries, events, and more that occurred in 1989.
June[]
- June 16: Proteus is discovered.
July[]
- July 28: Despina and Galatea are discovered.
August[]
September[]
- September 18: Thalassa and Naiad are discovered.
October[]
- October 18: Galileo spacecraft is launched.
Unknown date[]
- HD 114762 b is discovered.