Snapchat Planetsare part of Snapchat+’s Friend Solar System, which represents your position among another person’s top eight friends.
Each planet corresponds to a ranking, starting with Mercury for first place and ending with Neptune for eighth place.
Your position depends on your interactions through Snaps and Chats, so it can change as your activity changes.
The feature is optional, and you may need to enable the Friend Solar System in your Snapchat+ settings to see it.
Have you checked your planet recently, and did it match how often you interact with that friend?