From Wikitroid, the Metroid wiki

Cylosis is given as Sylux's origin in the opening cinematic of Metroid Prime: Hunters. Since Sylux is surrounded in mystery, it's debatable whether Cylosis is his actual homeworld, or simply where he stole his armor, the Delano 7, Shock Coil, and Lockjaw.

Planets in the Metroid Series
Note: Bolded Planets were visited by Samus Aran
Tetra Galaxy
Alinos | Arcterra
Ooromine System
Bilium | Ooromine II | Twin Tabula | Zebes | Tallon IV
Federation Solar System
Bryyo | Norion | Elysia
SR 388 System
SR227 | SR388
Other
Aether | Aliehs III | Bes III | Cylosis | Earth | Jovia XII | Earth Colony K-2L | Mondreus | Phaaze | Phrygis | Pirate Homeworld | Tivus | Vho | Wotan VII