| Answer | Crossword Clue |
|---|---|
| PLUTO | Planet beyond Neptune |
| PSI | Symbol of the planet Neptune |
| TRIDENT | Symbol of the planet Neptune |
| PLUTO | Beyond Neptune |
| PLUTO | Orb beyond Neptune |
| PLANETX | Hypothetical solar system body beyond Neptune |
| PLANETX | Hypothetical body in the solar system beyond Neptune |
| PLANETX | Term coined by Percival Lowell for a hypothetical world beyond Neptune |
