| Clue | Source | Date |
|---|---|---|
| Traveler's flight (X = RIP) | Universal | 15 Mar 2023 |
| Hypothetical solar system body beyond Neptune | New York Times | 20 Aug 2020 |
| Hypothetical body in the solar system beyond Neptune | New York Times | 14 Nov 2018 |
| Hypothetical body in the solar system beyond Neptune | ||
| Term coined by Percival Lowell for a hypothetical world beyond Neptune | ||
| Quest of the astronomer Percival Lowell |