Bilium is a planet in the FS-176 system. Its only mention was in the Space Pirate Observatory in Metroid Prime. A notable feature of the planet is that it is the closest planet to its star, FS-176. It is one of three known objects in the system to have a retrograde orbit, however it has a normal rotation. Otherwise, it has one of the most stable orbits and does not approach or cross paths with other planets like the rest in the system do. It is very close to a large asteroid field that encloses it in with its sun.

An unused scan in Metroid Prime Remastered names a Planet Miteralis. This name appears to have ultimately been repurposed for a virus present on Bilium.


"Planet Bilium
Mass: 3.8 trillion teratons.

Atmosphere is rife with Miteralis, a sentient gaseous Global Exterminator virus."


Bilium has 3 moons orbiting it, one of which has an incredibly low orbit.


  • Interestingly, the name Bilium carries the prefix, bili- (L. bilis; bile) and the suffix -um, which creates a noun indicating the presence of.
  • Animation data for the Observatory hologram gives Bilium the name '"GasPlanet". Considering its cloudy appearance, this may indicate that Bilium is a gas giant.
  • The Mass of 3.8 Trillion Teratons or 3.8×1027 kg by US English standards would give it a mass twice as much as planet Jupiter; which has a mass of 1.9×1027 kg. This would be consistent with Bilium being having descriptions indicating it being a gas giant.